Favorable Prognosis for Patients 12 to 18 Months of Age With Stage 4 Nonamplified MYCN Neuroblastoma: A Children's Cancer Group Study
http://www.100md.com
《临床肿瘤学》
the University of Illinois at Chicago, Chicago, IL
Children's Hospital & Research Center Oakland, Oakland
Children's Hospital of Los Angeles, Los Angeles
Children's Oncology Group, Arcadia
University of California, San Francisco School of Medicine, San Francisco, CA
Children's Hospital of Philadelphia
University of Pennsylvania School of Medicine, Philadelphia, PA
University of Minnesota, Minneapolis, MN
ABSTRACT
PURPOSE: The long-term survival of children between age 12 and 24 months with stage 4 neuroblastoma and nonamplified MYCN (MYCN-NA) has not been defined previously.
PATIENTS AND METHODS: Survival for stage 4 MYCN-NA neuroblastoma patients enrolled onto Children's Cancer Group (CCG) protocols 321P2 (1986 to 1991) and 3891 (1991 to 1996) was analyzed. Treatment consisted of intensive alkylator-based induction chemotherapy with or without autologous bone marrow transplantation (ABMT) with or without 13 cis-retinoic acid. Survival was analyzed by age strata less than 12, 12 to 18, 18 to 24, and more than 24 months at diagnosis. Patients younger than 12 months were treated on the moderate-intensity CCG protocol 3881.
RESULTS: Forty-three patients with stage 4 MYCN-NA disease enrolled onto CCG-321P2 (n = 17) or CCG-3891 (n = 26) were between 12 and 24 months of age at diagnosis. After a median follow-up of 94 months (range, 4 to 140 months), the 6-year event-free survival (EFS) for the 12- to 18-month age group was superior to that of the 18- to 24-month age group (74% ± 8% v 31% ± 12%; P = .008). The EFS for children older than 24 months with stage 4 MYCN-NA neuroblastoma was 23% ± 3%, and for children younger than 12 months was 92% ± 3%.
CONCLUSION: Children diagnosed with stage 4 MYCN-NA neuroblastoma in the second year of life form a transitional group between infants and older children in terms of prognosis. Patients between 12 and 18 months of age have significantly better long-term survival than that of older children treated with intensive chemotherapy with or without ABMT. These patients may not benefit from additional intensification of therapy beyond that provided in earlier clinical trials and may even maintain this high survival rate with less intensive therapy.
INTRODUCTION
Children with neuroblastoma exhibit marked variability in outcome when the disease is categorized by age, stage, and biologic characteristics.1-5 Efforts to improve the outcome of patients with neuroblastoma in the last decade have focused on identification of risk groups based on clinical and biologic variables as well as intensification of therapy for high-risk cases.1,6 Children older than 1 year with stage 4 neuroblastoma constitute the largest such category for which high-dose chemotherapy followed by autologous stem-cell transplantation is now routinely recommended.7
Infants younger than 12 months of age at diagnosis with stage 4 neuroblastoma and nonamplified MYCN (MYCN-NA) have an excellent prognosis when treated with moderate doses of chemotherapy.4 Genomic amplification of MYCN has a profound adverse influence on tumor behavior in infant neuroblastoma patients with metastatic disease. Three-year event-free survival (EFS) rates were 93% ± 4% v 10% ± 7% (P < .0001) based on the absence or presence of MYCN amplification despite significantly more intensive therapy for patients in the latter group.4 In contrast, the adverse prognostic influence of MYCN amplification is diluted in stage 4 patients older than 1 year of age at diagnosis, perhaps due to the poor outcome in general for this group. Within the large cohort of patients with metastatic disease and MYCN-NA, age at diagnosis remains the most important prognostic factor. However, the underlying basis for improved outcome in infants currently is unknown.
Children between 12 and 24 months of age with stage 4 disease currently are classified as high risk irrespective of MYCN status.1 However, although children with amplified MYCN have poor outcome at all ages, the prognosis in patients with MYCN-NA tumors may depend on additional tumor-specific and/or host biologic variables. From the therapeutic perspective, it is important to determine if the decreased EFS occurs in all patients older than 12 months, or whether children between 12 and 24 months of age with stage 4 MYCN-NA neuroblastoma constitute a transitional risk group.
PATIENTS AND METHODS
Patients
Between January 1991 and April 1996, 134 patients between 12 and 24 months of age were enrolled onto the Children's Cancer Group (CCG) -3891 protocol for treatment of high-risk neuroblastoma. A total of 109 patients had stage 4 disease, of whom 26 lacked MYCN amplification. An additional 17 patients enrolled onto the preceding CCG-321P2 study (also with stage 4 disease) who lacked MYCN amplification and were between 12 and 24 months of age were treated at CCG institutions between 1986 and 1991, and are also included in the current analysis (Table 1) . The outcome of these 43 patients was compared with children with stage 4 MYCN-NA neuroblastoma younger than 12 months of age who were treated with the less intensive CCG-3881 protocol (n = 68), and children older than 24 months treated with the CCG-3891 protocol (n = 165). All patients had informed consent forms signed by a parent or guardian and study approval by the CCG treatment center’s institutional review board.
MYCN gene amplification was determined either by Southern analysis (up to 1993) or on the basis of the pattern and intensity of the MYCN protein on immunohistochemical and semiquantitative polymerase chain reaction assays (after 1993).8-11 All tumors with adequate biopsy specimens were reviewed centrally and classified as favorable histology (FH) or unfavorable histology (UH) according to the method of Shimada et al.12,13
Treatment
The details of chemotherapy administered in the CCG-3891 protocol have been published.7 Briefly, CCG-3891 was a randomized trial during which children with high-risk neuroblastoma received initial therapy with cisplatin, doxorubicin, etoposide, and cyclophosphamide for five cycles, plus surgery and radiotherapy for gross residual disease. Patients were randomly assigned to receive autologous bone marrow transplantation (ABMT; after conditioning with carboplatin, etoposide, melphalan, and total-body irradiation) or continuation chemotherapy (CC) with three cycles of cisplatin, etoposide, doxorubicin, and ifosfamide. There was also a cohort of patients that was nonrandomly assigned to the nonmyeloablative regimen for a variety of reasons including physician or parent refusal of randomized assignment to treatment or insurance company refusal to pay for the ABMT. Patients without disease progression were then randomly assigned to receive 13-cis-retinoic acid (CRA) or no additional therapy. CCG-321P2 was a pilot study for the CCG-3891 randomized trial. P2 patients received the induction regimen for CCG-3891 and had the option to continue to ABMT on CCG-321P3.14 Infants treated on CCG-3881 received four-drug chemotherapy for 9 months (cisplatin, cyclophosphamide, doxorubicin, and etoposide), with surgery and local radiation only for gross residual disease.4
Statistical Analysis
Life-table methods were used to estimate the EFS and overall survival (OS) from the time of diagnosis. Elapsed time from time of diagnosis to an event or to end of follow-up was used to compute EFS and OS probabilities. The log-rank statistic was used to compare the EFS and OS probabilities between subgroups of patients.15 For just the comparison of the EFS of patients receiving ABMT versus those receiving CC on CCG-3891, elapsed time was computed either from time of ABMT (for those receiving ABMT) or from 190 days after study entry (for those receiving CC). The time point of 190 days from the beginning of follow-up for the CC group was chosen because it was equal to the median time of all patients receiving ABMT who were enrolled onto CCG-3891. In performing the analysis of pairwise comparisons of the EFS and OS curves by age groups, a conservative Bonferroni adjustment for multiple comparisons was used. For four age-group curves, there are three pairwise comparisons that can be performed; therefore, the significance level to which the P value is compared is lowered from .05 to .0167 (.05/3).
RESULTS
Patient Characteristics
Of the 808 patients enrolled onto the CCG-321P2/P3 and CCG-3891 trials, a total of 47 patients met the criteria for stage 4 MYCN-NA neuroblastoma and age 12 to 24 months at diagnosis. Patients enrolled onto CCG-321P3 (n = 4) were excluded from analysis because of differences in chemotherapy regimens. Of the remaining 43 patients, 26 were from CCG-3891 and 17 were from CCG-321P2 (Table 1). ABMT was performed in eight patients (six in the 12- to 18-month-old group and two in the 18- to 24-month-old group), 10 patients received CRA (five each in the 12- to 18-month-old group and 18- to 24-month-old group), and four patients received both ABMT and CRA (two in each age group). The number of transplantations in the CCG-3891 cohort (eight of 26 patients) approximates the ratio of transplantations for all of CCG-3891 and was due in large part to the nonrandom assignment to the consolidation chemotherapy regimen because of parental and/or physician choice. There were no deaths as a result of toxicity among the 12- to 24-month-old cohort of patients.
In the CCG-3881 and CCG-3891 studies, results of MYCN analysis were available for 414 (71%) of the 581 stage 4 patients. The prevalence of MYCN amplification was 35% for the entire group and displayed variation with age. The proportion of MYCN-amplified tumors increased to reach a peak of 67% between age 18 and 24 months, and then decreased gradually to 15% for older children. Children in the 12- to 24-month-old group exhibited the highest prevalence of MYCN amplification compared with any other group (Fig 1). Sixty-five percent of patients between 12 and 24 months of age had MYCN-amplified tumors as opposed to 29% of patients younger than 1 year, 36% between 2 and 4 years of age, and 15% of patients older than 4 years.
EFS and Biologic and Treatment Variables
With a median follow-up of 94 months (range, 4 to 140 months) the 6-year EFS ± SE was 74% ± 8% for the 12- to 18-month-old group (n = 27) and 31% ± 12% for the 18- to 24-month-old group (n = 16; P = .008; Fig 2A). The 6-year OS ± SE was 74% ± 9% for the 12- to 18-month-old group (n = 27) and 33% ± 12% for the 18- to 24-month-old group (n = 16; P = .022; Fig 2B).
A separate analysis of age and outcome for all patients with stage 4 MYCN-NA disease treated during CCG-3881 or CCG-3891 was completed. The 6-year EFS ± SE for children younger than 12 months with stage 4 MYCN-NA neuroblastoma (n = 68) treated on the less intensive CCG-3881 protocol was 92% ± 3%. Children 12 to 18 months of age with stage 4 MYCN-NA neuroblastoma (n = 15) treated during CCG-3891 had a 6-year EFS ± SE of 87% ± 9%. Children 18 to 24 months of age with stage 4 MYCN-NA neuroblastoma (n = 11) treated during CCG-3891 had a 6-year EFS ± SE of 36% ± 15%. Children older than 24 months with stage 4 MYCN-NA neuroblastoma (n = 165) treated during CCG-3891 had a 6-year EFS ± SE of 23% ± 3%. One or more of these age-group EFS curves was statistically significantly different from one another (P < .0001; Fig 3A). In a pairwise comparison of the stage 4 MYCN-NA patients who were younger than 12 (n = 68) v 12 to 18 months (n = 15), the EFS rates were not found to be statistically significantly different from one another (P = .523). However, a pairwise comparison of the stage 4 MYCN-NA patients who were age 12 to 18 (n = 15) v 18 to 24 months (n = 11) yielded EFS rates that were statistically significantly different from one another (P = .006).
The 6-year OS ± SE for children younger than 12 months with stage 4 MYCN-NA neuroblastoma (n = 68) treated on the less intensive CCG-3881 protocol was 97% ± 2%. Children 12 to 18 months of age with stage 4 MYCN-NA neuroblastoma (n = 15) treated during CCG-3891 had a 6-year OS ± SE of 86% ± 10%. Children age 18 to 24 months with stage 4 MYCN-NA neuroblastoma (n = 11) treated during CCG-3891 had a 6-year OS of 40% ± 16%. Children older than 24 months with stage 4 MYCN-NA neuroblastoma (n = 165) treated during CCG-3891 had a 6-year OS of 35% ± 4%. At least one (and perhaps more) of these age-group EFS curves were statistically significantly different from one another (P < .0001; Fig 3B). In a pairwise comparison of the stage 4 MYCN-NA patients who were younger than 12 (n = 68) v 12 to 18 months (n = 15), the OS rates were not found to be statistically significantly different from one another (P = .134). A pairwise comparison of the stage 4 MYCN-NA patients who were age 12 to 18 (n = 15) v 18 to 24 months (n = 11) yielded OS rates that were statistically significantly different from one another (P = .014).
Shimada histology correlated with age at diagnosis and survival. Results for Shimada classification were available for 25 patients (CCG-3891, n = 19; CCG-321P2, n = 6), 12 had FH and 13 had UH (Table 2). In the remaining 18 patients, tumors could not be classified according to the Shimada system because of insufficient biopsy specimen. The 6-year EFS was significantly better for patients with FH (92% ± 8%) compared with the UH group (46% ± 14%; P = .013). Nearly all patients with FH (11 of 12) were in the 12- to 18-month-old group. Only one of 10 patients 18 to 24 months of age had a tumor with FH; and only four of 15 patients 12 to 18 months of age had a tumor with UH. It is notable that three of four patients with UH who were 12 to 18 months old have survived without relapse.
ABMT was performed in eight patients enrolled onto the CCG-3891 protocol. ABMT was performed at the assigned time in the protocol (four patients), later (three patients), or after relapse (one patient). The EFS at 6 years ± SE for the four patients who underwent ABMT at the assigned time on CCG-3891 was 100% ± 0%, compared with 69% ± 13% for the 13 patients who received CC at the assigned time during CCG-3891 (P = .236). When patients 12 to 18 months of age from the CCG-3891 study were analyzed separately, none of the three patients undergoing ABMT at the protocol-assigned time experienced relapse, whereas one of the three patients undergoing ABMT during follow-up experienced relapse. None of the eight patients receiving CC at the protocol-assigned time experienced relapse (Table 2).
Biologic therapy with CRA was given to 10 patients in this cohort and treated during CCG-3891 (Table 2). Five of the 14 eligible patients 12 to 18 months of age received CRA. Four patients survived, as did nine of nine other 12- to 18-month-old patients who did not receive CRA. Five of seven eligible patients 18 to 24 months of age received CRA. Three of five survived, as did one of two patients who did not receive CRA in this age group.
DISCUSSION
Recent reports suggest that children with stage 4 MYCN-NA neuroblastoma can be subdivided into risk categories based on clinical or biologic characteristics.2,4,5 Tumor histology,5 age at diagnosis,4 tumor cell ploidy,16 and genomic copy number alterations at 1p36, 11q23,17,18 and 17q23-25 may have a significant impact on disease outcome. Age remains a powerful predictor of prognosis in this group of patients, with infants exhibiting 93% EFS at 3 years4 with moderate-intensity therapy. However, only one third of the patients older than 1 year of age at diagnosis are expected to survive with the current dose-intensive regimens, including myeloablative consolidation therapy.6,7 Historically, age at diagnosis has been considered as a dichotomous variable. As risk stratification algorithms evolve, reanalysis of age as a continuous variable, as originally suggested by the analysis of Breslow and McCann,19 seems warranted.
The purpose of this study was to examine the hypothesis that patients with stage 4 MYCN-NA disease who are 1 to 2 years of age have a similarly favorable prognosis as infants younger than 1 year of age. This could lead to a more precise risk assignment and could significantly affect treatment recommendations for these patients.
In this analysis, children in the 12- to 18-month-old group treated during CCG-321P2 and CCG-3891 had an EFS and OS that was not statistically different from infants younger than 12 months treated on the less intensive CCG-3881 protocol. Increased treatment intensity could have contributed to the improved survival of children between 12 and 18 months of age. However, children in the 18- to 24-month-old group fared as poorly as those older than 24 months, despite receiving similar therapy. The superior survival of stage 4 patients between 12 and 24 months of age has been noted before. In a study of 218 patients older than 1 year of age with stage 4 neuroblastoma treated at a single institution between 1980 and 1996, the relative risk of relapse in patients older than 24 months at diagnosis was 1.83 (P = .012) compared with 12- to 24-month-old patients.20 A previous analysis of CCG-321P2 and CCG-321P3 trials also observed better outcome in the 12- to 24-month-old patients.21 However, additional classification based on age and MYCN status was not performed in either of these reports. The current analysis of the combined data from CCG trials suggests that the basis for the previously reported improved survival of the 12- to 24-month-old group of patients is probably related to the excellent outcome of the patients between 12 and 18 months of age with MYCN-NA neuroblastoma. The outcome of these patients seems to be much more favorable and similar to that of the infants younger than 12 months than to the patients older than 2 years of age. The infants, however, demonstrate excellent outcome with a much less intensive and nonmyeloablative chemotherapy4 (CCG-3881) than is currently recommended for all children with disseminated neuroblastoma who are older than 12 months at diagnosis.
Within the 12- to 18-month-old group, the benefit of ABMT was inconclusive because of the small number of assessable patients in each group. In the CCG-3891 protocol, five of six patients between 12 and 18 months of age who underwent ABMT survived, compared with eight of eight who received consolidation chemotherapy alone. This observation is comparable to the previously reported CCG-321P2 and CCG-321P3 data, for which no effect of ABMT on survival of 12- to 24-month-old patients (stage 4, any MYCN status) was demonstrable (4-year EFS, 62% for ABMT group v 60% for chemotherapy group; P = .720).21
The Shimada classification system, based on patient age and histologic features, is an independent predictor of survival in neuroblastoma.22 This is an age-linked classification system with children younger than 18 months with poorly differentiated or differentiating tumors, and low to intermediate mitosis-karyorrhexis index considered FH. Among children older than 18 months, only those with differentiating tumors or low mitosis-karyorrhexis index are classified as FH. Given that this age criterion corresponds to the threshold for poor prognosis in the current analysis, the relationship of age at diagnosis to Shimada classification in 12- to 24-month-old patients was examined. In the 25 patients for whom information was available, the majority of patients age 12 to 18 months had FH (11 of 15), and those in the 18- to 24-month-old group had UH (nine of 10). In the 12- to 18-month-old group, three of four patients with UH survived compared with survival in only three of nine patients with UH in the 18- to 24-month-old group. This suggests that covariates of age and Shimada pathology are closely linked and do not add independent prognostic information in the 12- to 18-month-old group.
Tumor cell ploidy (DNA content) can help to distinguish between good and poor responders to chemotherapy in children younger than 2 years.16 In 34 children 12 to 24 months old with metastatic neuroblastoma, patients with hyperdiploid tumors had significantly better outcome compared with those with diploid tumors.16 Tumor ploidy was not determined in our study. With an OS of 97% for infants with MYCN-NA stage 4 neuroblastoma, and with the biostatistically similar outcome results in the patients 12 to 18 months old with MYCN-NA stage 4 disease, it may be difficult to identify an independent prognostic power for tumor cell ploidy in these groups using current therapy.
MYCN amplification status has been widely studied as a molecular marker to identify poor-risk patients1 and plays an important role in the Children’s Oncology Group risk assignment schema. The impact of MYCN amplification on prognosis was illustrated dramatically in infants with stage 4 neuroblastoma, in whom the 3-year EFS of patients with MYCN-amplified tumors was just 10% compared with 93% in those with MYCN-NA tumors.4 The observation of the previously unreported relationship of MYCN amplification with age in stage 4 neuroblastoma supports the concept of age-dependent genetic changes. In the CCG-3881 and CCG-3891 studies, the overall prevalence of MYCN amplification was 35% among children with stage 4 neuroblastoma, which is comparable to that in previous reports.9,16 When the prevalence of MYCN amplification was examined by age, children between the ages of 12 and 24 months had a much higher prevalence of MYCN amplification (65%) than at any other age. It is important to emphasize that these studies were open concomitantly for all newly diagnosed neuroblastoma patients; therefore, these data likely reflect the true natural history of the disease including the prevalence of MYCN amplification within various age groups. The 67% prevalence of MYCN amplification in our cohort of 18- to 24-month-old patients is remarkable, as is the age-dependent variation in this prevalence (Fig 1).
Taken together, these observations suggest a model for stage 4 MYCN-NA neuroblastoma. We hypothesize that age is a surrogate marker for tumor biology, with tumors from younger patients more likely to show hyperdiploidy, with few (if any) additional structural chromosomal rearrangements. Tumors from older children are more likely to show genetic instability, with unbalanced chromosomal deletions or gains including genomic amplification of MYCN. The excellent prognosis for patients 12 to 18 months of age reported in this study suggests that the molecular profile for the majority of these patients is more like that of the patients younger than 12 months. All other patients older than 18 months reflect a different tumor genetic profile with a much worse prognosis despite intensive multimodal therapy. Future studies should determine if tumor-specific molecular biologic variables other than MYCN might predict outcome independent of age in patients with metastatic neuroblastoma.
The current Children’s Oncology Group neuroblastoma risk stratification system and the International Neuroblastoma Risk Groups assign children with stage 4 disease to the high-risk group if they are at least 365 days old at the time of diagnosis, irrespective of the MYCN status.1,6 Currently, such patients are recommended to receive significantly more intensive induction and consolidation therapy, including myeloablative therapy with autologous stem-cell rescue, compared with the CCG-3891 trial. The results here suggest that the prognosis for children between 12 to 18 months of age with stage 4 MYCN-NA disease is excellent with the treatment administered during CCG-3891, with or without myeloablative consolidation, and with or without CRA.
Authors' Disclosures of Potential Conflicts of Interest
The authors indicated no potential conflicts of interest.
NOTES
Authors' disclosures of potential conflicts of interest are found at the end of this article.
REFERENCES
Castleberry RP, Pritchard J, Ambros P, et al: The International Neuroblastoma Risk Groups (INRG): A preliminary report. Eur J Cancer 33:2113-2116, 1997
Maris JM, Matthay KK: Molecular biology of neuroblastoma. J Clin Oncol 17:2264-2279, 1999
Brodeur GM, Pritchard J, Berthold F, et al: Revisions of the international criteria for neuroblastoma diagnosis, staging, and response to treatment. J Clin Oncol 11:1466-1477, 1993
Schmidt ML, Lukens JN, Seeger RC, et al: Biologic factors determine prognosis in infants with stage IV neuroblastoma: A prospective Children's Cancer Group study. J Clin Oncol 18:1260-1268, 2000
Goto S, Umehara S, Gerbing RB, et al: Histopathology (International Neuroblastoma Pathology Classification) and MYCN status in patients with peripheral neuroblastic tumors: A report from the Children's Cancer Group. Cancer 92:2699-2708, 2001
Matthay KK: Intensification of therapy using hematopoietic stem-cell support for high-risk neuroblastoma. Pediatr Transplant 3:72-77, 1999 (suppl 1)
Matthay KK, Villablanca JG, Seeger RC, et al: Treatment of high-risk neuroblastoma with intensive chemotherapy, radiotherapy, autologous bone marrow transplantation, and 13-cis-retinoic acid: Children's Cancer Group. N Engl J Med 341:1165-1173, 1999
Brodeur GM, Seeger RC, Schwab M, et al: Amplification of N-myc in untreated human neuroblastomas correlates with advanced disease stage. Science 224:1121-1124, 1984
Seeger RC, Brodeur GM, Sather H, et al: Association of multiple copies of the N-myc oncogene with rapid progression of neuroblastomas. N Engl J Med 313:1111-1116, 1985
Seeger RC, Wada R, Brodeur GM, et al: Expression of N-myc by neuroblastomas with one or multiple copies of the oncogene. Prog Clin Biol Res 271:41-49, 1988
Crabbe DC, Peters J, Seeger RC: Rapid detection of MYCN gene amplification in neuroblastomas using the polymerase chain reaction. Diagn Mol Pathol 1:229-234, 1992
Shimada H, Chatten J, Newton WA Jr, et al: Histopathologic prognostic factors in neuroblastic tumors: Definition of subtypes of ganglioneuroblastoma and an age-linked classification of neuroblastomas. J Natl Cancer Inst 73:405-416, 1984
Chatten J, Shimada H, Sather HN, et al: Prognostic value of histopathology in advanced neuroblastoma: A report from the Childrens Cancer Study Group. Hum Pathol 19:1187-1198, 1988
Stram DO, Matthay KK, O'Leary M, et al: Myeloablative chemoradiotherapy versus continued chemotherapy for high risk neuroblastoma. Prog Clin Biol Res 385:287-291, 1994
Kaplan EL, Meier P: Nonparametric estimation from incomplete observations. J Am Stat Assoc 53:457-481, 1958
Look AT, Hayes FA, Shuster JJ, et al: Clinical relevance of tumor cell ploidy and N-myc gene amplification in childhood neuroblastoma: A Pediatric Oncology Group study. J Clin Oncol 9:581-591, 1991
Guo C, White PS, Hogarty MD, et al: Deletion of 11q23 is a frequent event in the evolution of MYCN single-copy high-risk neuroblastomas. Med Pediatr Oncol 35:544-546, 2000
Luttikhuis ME, Powell JE, Rees SA, et al: Neuroblastomas with chromosome 11q loss and single copy MYCN comprise a biologically distinct group of tumours with adverse prognosis. Br J Cancer 85:531-537, 2001
Breslow N, McCann B: Statistical estimation of prognosis for children with neuroblastoma. Cancer Res 31:2098-2103, 1971
Hartmann O, Valteau-Couanet D, Vassal G, et al: Prognostic factors in metastatic neuroblastoma in patients over 1 year of age treated with high-dose chemotherapy and stem cell transplantation: A multivariate analysis in 218 patients treated in a single institution. Bone Marrow Transplant 23:789-795, 1999
Stram DO, Matthay KK, O'Leary M, et al: Consolidation chemoradiotherapy and autologous bone marrow transplantation versus continued chemotherapy for metastatic neuroblastoma: A report of two concurrent Children's Cancer Group studies. J Clin Oncol 14:2417-2426, 1996
Shimada H, Umehara S, Monobe Y, et al: International neuroblastoma pathology classification for prognostic evaluation of patients with peripheral neuroblastic tumors: A report from the Children's Cancer Group. Cancer 92:2451-2461, 2001(Mary Lou Schmidt, Ashutos)
Children's Hospital & Research Center Oakland, Oakland
Children's Hospital of Los Angeles, Los Angeles
Children's Oncology Group, Arcadia
University of California, San Francisco School of Medicine, San Francisco, CA
Children's Hospital of Philadelphia
University of Pennsylvania School of Medicine, Philadelphia, PA
University of Minnesota, Minneapolis, MN
ABSTRACT
PURPOSE: The long-term survival of children between age 12 and 24 months with stage 4 neuroblastoma and nonamplified MYCN (MYCN-NA) has not been defined previously.
PATIENTS AND METHODS: Survival for stage 4 MYCN-NA neuroblastoma patients enrolled onto Children's Cancer Group (CCG) protocols 321P2 (1986 to 1991) and 3891 (1991 to 1996) was analyzed. Treatment consisted of intensive alkylator-based induction chemotherapy with or without autologous bone marrow transplantation (ABMT) with or without 13 cis-retinoic acid. Survival was analyzed by age strata less than 12, 12 to 18, 18 to 24, and more than 24 months at diagnosis. Patients younger than 12 months were treated on the moderate-intensity CCG protocol 3881.
RESULTS: Forty-three patients with stage 4 MYCN-NA disease enrolled onto CCG-321P2 (n = 17) or CCG-3891 (n = 26) were between 12 and 24 months of age at diagnosis. After a median follow-up of 94 months (range, 4 to 140 months), the 6-year event-free survival (EFS) for the 12- to 18-month age group was superior to that of the 18- to 24-month age group (74% ± 8% v 31% ± 12%; P = .008). The EFS for children older than 24 months with stage 4 MYCN-NA neuroblastoma was 23% ± 3%, and for children younger than 12 months was 92% ± 3%.
CONCLUSION: Children diagnosed with stage 4 MYCN-NA neuroblastoma in the second year of life form a transitional group between infants and older children in terms of prognosis. Patients between 12 and 18 months of age have significantly better long-term survival than that of older children treated with intensive chemotherapy with or without ABMT. These patients may not benefit from additional intensification of therapy beyond that provided in earlier clinical trials and may even maintain this high survival rate with less intensive therapy.
INTRODUCTION
Children with neuroblastoma exhibit marked variability in outcome when the disease is categorized by age, stage, and biologic characteristics.1-5 Efforts to improve the outcome of patients with neuroblastoma in the last decade have focused on identification of risk groups based on clinical and biologic variables as well as intensification of therapy for high-risk cases.1,6 Children older than 1 year with stage 4 neuroblastoma constitute the largest such category for which high-dose chemotherapy followed by autologous stem-cell transplantation is now routinely recommended.7
Infants younger than 12 months of age at diagnosis with stage 4 neuroblastoma and nonamplified MYCN (MYCN-NA) have an excellent prognosis when treated with moderate doses of chemotherapy.4 Genomic amplification of MYCN has a profound adverse influence on tumor behavior in infant neuroblastoma patients with metastatic disease. Three-year event-free survival (EFS) rates were 93% ± 4% v 10% ± 7% (P < .0001) based on the absence or presence of MYCN amplification despite significantly more intensive therapy for patients in the latter group.4 In contrast, the adverse prognostic influence of MYCN amplification is diluted in stage 4 patients older than 1 year of age at diagnosis, perhaps due to the poor outcome in general for this group. Within the large cohort of patients with metastatic disease and MYCN-NA, age at diagnosis remains the most important prognostic factor. However, the underlying basis for improved outcome in infants currently is unknown.
Children between 12 and 24 months of age with stage 4 disease currently are classified as high risk irrespective of MYCN status.1 However, although children with amplified MYCN have poor outcome at all ages, the prognosis in patients with MYCN-NA tumors may depend on additional tumor-specific and/or host biologic variables. From the therapeutic perspective, it is important to determine if the decreased EFS occurs in all patients older than 12 months, or whether children between 12 and 24 months of age with stage 4 MYCN-NA neuroblastoma constitute a transitional risk group.
PATIENTS AND METHODS
Patients
Between January 1991 and April 1996, 134 patients between 12 and 24 months of age were enrolled onto the Children's Cancer Group (CCG) -3891 protocol for treatment of high-risk neuroblastoma. A total of 109 patients had stage 4 disease, of whom 26 lacked MYCN amplification. An additional 17 patients enrolled onto the preceding CCG-321P2 study (also with stage 4 disease) who lacked MYCN amplification and were between 12 and 24 months of age were treated at CCG institutions between 1986 and 1991, and are also included in the current analysis (Table 1) . The outcome of these 43 patients was compared with children with stage 4 MYCN-NA neuroblastoma younger than 12 months of age who were treated with the less intensive CCG-3881 protocol (n = 68), and children older than 24 months treated with the CCG-3891 protocol (n = 165). All patients had informed consent forms signed by a parent or guardian and study approval by the CCG treatment center’s institutional review board.
MYCN gene amplification was determined either by Southern analysis (up to 1993) or on the basis of the pattern and intensity of the MYCN protein on immunohistochemical and semiquantitative polymerase chain reaction assays (after 1993).8-11 All tumors with adequate biopsy specimens were reviewed centrally and classified as favorable histology (FH) or unfavorable histology (UH) according to the method of Shimada et al.12,13
Treatment
The details of chemotherapy administered in the CCG-3891 protocol have been published.7 Briefly, CCG-3891 was a randomized trial during which children with high-risk neuroblastoma received initial therapy with cisplatin, doxorubicin, etoposide, and cyclophosphamide for five cycles, plus surgery and radiotherapy for gross residual disease. Patients were randomly assigned to receive autologous bone marrow transplantation (ABMT; after conditioning with carboplatin, etoposide, melphalan, and total-body irradiation) or continuation chemotherapy (CC) with three cycles of cisplatin, etoposide, doxorubicin, and ifosfamide. There was also a cohort of patients that was nonrandomly assigned to the nonmyeloablative regimen for a variety of reasons including physician or parent refusal of randomized assignment to treatment or insurance company refusal to pay for the ABMT. Patients without disease progression were then randomly assigned to receive 13-cis-retinoic acid (CRA) or no additional therapy. CCG-321P2 was a pilot study for the CCG-3891 randomized trial. P2 patients received the induction regimen for CCG-3891 and had the option to continue to ABMT on CCG-321P3.14 Infants treated on CCG-3881 received four-drug chemotherapy for 9 months (cisplatin, cyclophosphamide, doxorubicin, and etoposide), with surgery and local radiation only for gross residual disease.4
Statistical Analysis
Life-table methods were used to estimate the EFS and overall survival (OS) from the time of diagnosis. Elapsed time from time of diagnosis to an event or to end of follow-up was used to compute EFS and OS probabilities. The log-rank statistic was used to compare the EFS and OS probabilities between subgroups of patients.15 For just the comparison of the EFS of patients receiving ABMT versus those receiving CC on CCG-3891, elapsed time was computed either from time of ABMT (for those receiving ABMT) or from 190 days after study entry (for those receiving CC). The time point of 190 days from the beginning of follow-up for the CC group was chosen because it was equal to the median time of all patients receiving ABMT who were enrolled onto CCG-3891. In performing the analysis of pairwise comparisons of the EFS and OS curves by age groups, a conservative Bonferroni adjustment for multiple comparisons was used. For four age-group curves, there are three pairwise comparisons that can be performed; therefore, the significance level to which the P value is compared is lowered from .05 to .0167 (.05/3).
RESULTS
Patient Characteristics
Of the 808 patients enrolled onto the CCG-321P2/P3 and CCG-3891 trials, a total of 47 patients met the criteria for stage 4 MYCN-NA neuroblastoma and age 12 to 24 months at diagnosis. Patients enrolled onto CCG-321P3 (n = 4) were excluded from analysis because of differences in chemotherapy regimens. Of the remaining 43 patients, 26 were from CCG-3891 and 17 were from CCG-321P2 (Table 1). ABMT was performed in eight patients (six in the 12- to 18-month-old group and two in the 18- to 24-month-old group), 10 patients received CRA (five each in the 12- to 18-month-old group and 18- to 24-month-old group), and four patients received both ABMT and CRA (two in each age group). The number of transplantations in the CCG-3891 cohort (eight of 26 patients) approximates the ratio of transplantations for all of CCG-3891 and was due in large part to the nonrandom assignment to the consolidation chemotherapy regimen because of parental and/or physician choice. There were no deaths as a result of toxicity among the 12- to 24-month-old cohort of patients.
In the CCG-3881 and CCG-3891 studies, results of MYCN analysis were available for 414 (71%) of the 581 stage 4 patients. The prevalence of MYCN amplification was 35% for the entire group and displayed variation with age. The proportion of MYCN-amplified tumors increased to reach a peak of 67% between age 18 and 24 months, and then decreased gradually to 15% for older children. Children in the 12- to 24-month-old group exhibited the highest prevalence of MYCN amplification compared with any other group (Fig 1). Sixty-five percent of patients between 12 and 24 months of age had MYCN-amplified tumors as opposed to 29% of patients younger than 1 year, 36% between 2 and 4 years of age, and 15% of patients older than 4 years.
EFS and Biologic and Treatment Variables
With a median follow-up of 94 months (range, 4 to 140 months) the 6-year EFS ± SE was 74% ± 8% for the 12- to 18-month-old group (n = 27) and 31% ± 12% for the 18- to 24-month-old group (n = 16; P = .008; Fig 2A). The 6-year OS ± SE was 74% ± 9% for the 12- to 18-month-old group (n = 27) and 33% ± 12% for the 18- to 24-month-old group (n = 16; P = .022; Fig 2B).
A separate analysis of age and outcome for all patients with stage 4 MYCN-NA disease treated during CCG-3881 or CCG-3891 was completed. The 6-year EFS ± SE for children younger than 12 months with stage 4 MYCN-NA neuroblastoma (n = 68) treated on the less intensive CCG-3881 protocol was 92% ± 3%. Children 12 to 18 months of age with stage 4 MYCN-NA neuroblastoma (n = 15) treated during CCG-3891 had a 6-year EFS ± SE of 87% ± 9%. Children 18 to 24 months of age with stage 4 MYCN-NA neuroblastoma (n = 11) treated during CCG-3891 had a 6-year EFS ± SE of 36% ± 15%. Children older than 24 months with stage 4 MYCN-NA neuroblastoma (n = 165) treated during CCG-3891 had a 6-year EFS ± SE of 23% ± 3%. One or more of these age-group EFS curves was statistically significantly different from one another (P < .0001; Fig 3A). In a pairwise comparison of the stage 4 MYCN-NA patients who were younger than 12 (n = 68) v 12 to 18 months (n = 15), the EFS rates were not found to be statistically significantly different from one another (P = .523). However, a pairwise comparison of the stage 4 MYCN-NA patients who were age 12 to 18 (n = 15) v 18 to 24 months (n = 11) yielded EFS rates that were statistically significantly different from one another (P = .006).
The 6-year OS ± SE for children younger than 12 months with stage 4 MYCN-NA neuroblastoma (n = 68) treated on the less intensive CCG-3881 protocol was 97% ± 2%. Children 12 to 18 months of age with stage 4 MYCN-NA neuroblastoma (n = 15) treated during CCG-3891 had a 6-year OS ± SE of 86% ± 10%. Children age 18 to 24 months with stage 4 MYCN-NA neuroblastoma (n = 11) treated during CCG-3891 had a 6-year OS of 40% ± 16%. Children older than 24 months with stage 4 MYCN-NA neuroblastoma (n = 165) treated during CCG-3891 had a 6-year OS of 35% ± 4%. At least one (and perhaps more) of these age-group EFS curves were statistically significantly different from one another (P < .0001; Fig 3B). In a pairwise comparison of the stage 4 MYCN-NA patients who were younger than 12 (n = 68) v 12 to 18 months (n = 15), the OS rates were not found to be statistically significantly different from one another (P = .134). A pairwise comparison of the stage 4 MYCN-NA patients who were age 12 to 18 (n = 15) v 18 to 24 months (n = 11) yielded OS rates that were statistically significantly different from one another (P = .014).
Shimada histology correlated with age at diagnosis and survival. Results for Shimada classification were available for 25 patients (CCG-3891, n = 19; CCG-321P2, n = 6), 12 had FH and 13 had UH (Table 2). In the remaining 18 patients, tumors could not be classified according to the Shimada system because of insufficient biopsy specimen. The 6-year EFS was significantly better for patients with FH (92% ± 8%) compared with the UH group (46% ± 14%; P = .013). Nearly all patients with FH (11 of 12) were in the 12- to 18-month-old group. Only one of 10 patients 18 to 24 months of age had a tumor with FH; and only four of 15 patients 12 to 18 months of age had a tumor with UH. It is notable that three of four patients with UH who were 12 to 18 months old have survived without relapse.
ABMT was performed in eight patients enrolled onto the CCG-3891 protocol. ABMT was performed at the assigned time in the protocol (four patients), later (three patients), or after relapse (one patient). The EFS at 6 years ± SE for the four patients who underwent ABMT at the assigned time on CCG-3891 was 100% ± 0%, compared with 69% ± 13% for the 13 patients who received CC at the assigned time during CCG-3891 (P = .236). When patients 12 to 18 months of age from the CCG-3891 study were analyzed separately, none of the three patients undergoing ABMT at the protocol-assigned time experienced relapse, whereas one of the three patients undergoing ABMT during follow-up experienced relapse. None of the eight patients receiving CC at the protocol-assigned time experienced relapse (Table 2).
Biologic therapy with CRA was given to 10 patients in this cohort and treated during CCG-3891 (Table 2). Five of the 14 eligible patients 12 to 18 months of age received CRA. Four patients survived, as did nine of nine other 12- to 18-month-old patients who did not receive CRA. Five of seven eligible patients 18 to 24 months of age received CRA. Three of five survived, as did one of two patients who did not receive CRA in this age group.
DISCUSSION
Recent reports suggest that children with stage 4 MYCN-NA neuroblastoma can be subdivided into risk categories based on clinical or biologic characteristics.2,4,5 Tumor histology,5 age at diagnosis,4 tumor cell ploidy,16 and genomic copy number alterations at 1p36, 11q23,17,18 and 17q23-25 may have a significant impact on disease outcome. Age remains a powerful predictor of prognosis in this group of patients, with infants exhibiting 93% EFS at 3 years4 with moderate-intensity therapy. However, only one third of the patients older than 1 year of age at diagnosis are expected to survive with the current dose-intensive regimens, including myeloablative consolidation therapy.6,7 Historically, age at diagnosis has been considered as a dichotomous variable. As risk stratification algorithms evolve, reanalysis of age as a continuous variable, as originally suggested by the analysis of Breslow and McCann,19 seems warranted.
The purpose of this study was to examine the hypothesis that patients with stage 4 MYCN-NA disease who are 1 to 2 years of age have a similarly favorable prognosis as infants younger than 1 year of age. This could lead to a more precise risk assignment and could significantly affect treatment recommendations for these patients.
In this analysis, children in the 12- to 18-month-old group treated during CCG-321P2 and CCG-3891 had an EFS and OS that was not statistically different from infants younger than 12 months treated on the less intensive CCG-3881 protocol. Increased treatment intensity could have contributed to the improved survival of children between 12 and 18 months of age. However, children in the 18- to 24-month-old group fared as poorly as those older than 24 months, despite receiving similar therapy. The superior survival of stage 4 patients between 12 and 24 months of age has been noted before. In a study of 218 patients older than 1 year of age with stage 4 neuroblastoma treated at a single institution between 1980 and 1996, the relative risk of relapse in patients older than 24 months at diagnosis was 1.83 (P = .012) compared with 12- to 24-month-old patients.20 A previous analysis of CCG-321P2 and CCG-321P3 trials also observed better outcome in the 12- to 24-month-old patients.21 However, additional classification based on age and MYCN status was not performed in either of these reports. The current analysis of the combined data from CCG trials suggests that the basis for the previously reported improved survival of the 12- to 24-month-old group of patients is probably related to the excellent outcome of the patients between 12 and 18 months of age with MYCN-NA neuroblastoma. The outcome of these patients seems to be much more favorable and similar to that of the infants younger than 12 months than to the patients older than 2 years of age. The infants, however, demonstrate excellent outcome with a much less intensive and nonmyeloablative chemotherapy4 (CCG-3881) than is currently recommended for all children with disseminated neuroblastoma who are older than 12 months at diagnosis.
Within the 12- to 18-month-old group, the benefit of ABMT was inconclusive because of the small number of assessable patients in each group. In the CCG-3891 protocol, five of six patients between 12 and 18 months of age who underwent ABMT survived, compared with eight of eight who received consolidation chemotherapy alone. This observation is comparable to the previously reported CCG-321P2 and CCG-321P3 data, for which no effect of ABMT on survival of 12- to 24-month-old patients (stage 4, any MYCN status) was demonstrable (4-year EFS, 62% for ABMT group v 60% for chemotherapy group; P = .720).21
The Shimada classification system, based on patient age and histologic features, is an independent predictor of survival in neuroblastoma.22 This is an age-linked classification system with children younger than 18 months with poorly differentiated or differentiating tumors, and low to intermediate mitosis-karyorrhexis index considered FH. Among children older than 18 months, only those with differentiating tumors or low mitosis-karyorrhexis index are classified as FH. Given that this age criterion corresponds to the threshold for poor prognosis in the current analysis, the relationship of age at diagnosis to Shimada classification in 12- to 24-month-old patients was examined. In the 25 patients for whom information was available, the majority of patients age 12 to 18 months had FH (11 of 15), and those in the 18- to 24-month-old group had UH (nine of 10). In the 12- to 18-month-old group, three of four patients with UH survived compared with survival in only three of nine patients with UH in the 18- to 24-month-old group. This suggests that covariates of age and Shimada pathology are closely linked and do not add independent prognostic information in the 12- to 18-month-old group.
Tumor cell ploidy (DNA content) can help to distinguish between good and poor responders to chemotherapy in children younger than 2 years.16 In 34 children 12 to 24 months old with metastatic neuroblastoma, patients with hyperdiploid tumors had significantly better outcome compared with those with diploid tumors.16 Tumor ploidy was not determined in our study. With an OS of 97% for infants with MYCN-NA stage 4 neuroblastoma, and with the biostatistically similar outcome results in the patients 12 to 18 months old with MYCN-NA stage 4 disease, it may be difficult to identify an independent prognostic power for tumor cell ploidy in these groups using current therapy.
MYCN amplification status has been widely studied as a molecular marker to identify poor-risk patients1 and plays an important role in the Children’s Oncology Group risk assignment schema. The impact of MYCN amplification on prognosis was illustrated dramatically in infants with stage 4 neuroblastoma, in whom the 3-year EFS of patients with MYCN-amplified tumors was just 10% compared with 93% in those with MYCN-NA tumors.4 The observation of the previously unreported relationship of MYCN amplification with age in stage 4 neuroblastoma supports the concept of age-dependent genetic changes. In the CCG-3881 and CCG-3891 studies, the overall prevalence of MYCN amplification was 35% among children with stage 4 neuroblastoma, which is comparable to that in previous reports.9,16 When the prevalence of MYCN amplification was examined by age, children between the ages of 12 and 24 months had a much higher prevalence of MYCN amplification (65%) than at any other age. It is important to emphasize that these studies were open concomitantly for all newly diagnosed neuroblastoma patients; therefore, these data likely reflect the true natural history of the disease including the prevalence of MYCN amplification within various age groups. The 67% prevalence of MYCN amplification in our cohort of 18- to 24-month-old patients is remarkable, as is the age-dependent variation in this prevalence (Fig 1).
Taken together, these observations suggest a model for stage 4 MYCN-NA neuroblastoma. We hypothesize that age is a surrogate marker for tumor biology, with tumors from younger patients more likely to show hyperdiploidy, with few (if any) additional structural chromosomal rearrangements. Tumors from older children are more likely to show genetic instability, with unbalanced chromosomal deletions or gains including genomic amplification of MYCN. The excellent prognosis for patients 12 to 18 months of age reported in this study suggests that the molecular profile for the majority of these patients is more like that of the patients younger than 12 months. All other patients older than 18 months reflect a different tumor genetic profile with a much worse prognosis despite intensive multimodal therapy. Future studies should determine if tumor-specific molecular biologic variables other than MYCN might predict outcome independent of age in patients with metastatic neuroblastoma.
The current Children’s Oncology Group neuroblastoma risk stratification system and the International Neuroblastoma Risk Groups assign children with stage 4 disease to the high-risk group if they are at least 365 days old at the time of diagnosis, irrespective of the MYCN status.1,6 Currently, such patients are recommended to receive significantly more intensive induction and consolidation therapy, including myeloablative therapy with autologous stem-cell rescue, compared with the CCG-3891 trial. The results here suggest that the prognosis for children between 12 to 18 months of age with stage 4 MYCN-NA disease is excellent with the treatment administered during CCG-3891, with or without myeloablative consolidation, and with or without CRA.
Authors' Disclosures of Potential Conflicts of Interest
The authors indicated no potential conflicts of interest.
NOTES
Authors' disclosures of potential conflicts of interest are found at the end of this article.
REFERENCES
Castleberry RP, Pritchard J, Ambros P, et al: The International Neuroblastoma Risk Groups (INRG): A preliminary report. Eur J Cancer 33:2113-2116, 1997
Maris JM, Matthay KK: Molecular biology of neuroblastoma. J Clin Oncol 17:2264-2279, 1999
Brodeur GM, Pritchard J, Berthold F, et al: Revisions of the international criteria for neuroblastoma diagnosis, staging, and response to treatment. J Clin Oncol 11:1466-1477, 1993
Schmidt ML, Lukens JN, Seeger RC, et al: Biologic factors determine prognosis in infants with stage IV neuroblastoma: A prospective Children's Cancer Group study. J Clin Oncol 18:1260-1268, 2000
Goto S, Umehara S, Gerbing RB, et al: Histopathology (International Neuroblastoma Pathology Classification) and MYCN status in patients with peripheral neuroblastic tumors: A report from the Children's Cancer Group. Cancer 92:2699-2708, 2001
Matthay KK: Intensification of therapy using hematopoietic stem-cell support for high-risk neuroblastoma. Pediatr Transplant 3:72-77, 1999 (suppl 1)
Matthay KK, Villablanca JG, Seeger RC, et al: Treatment of high-risk neuroblastoma with intensive chemotherapy, radiotherapy, autologous bone marrow transplantation, and 13-cis-retinoic acid: Children's Cancer Group. N Engl J Med 341:1165-1173, 1999
Brodeur GM, Seeger RC, Schwab M, et al: Amplification of N-myc in untreated human neuroblastomas correlates with advanced disease stage. Science 224:1121-1124, 1984
Seeger RC, Brodeur GM, Sather H, et al: Association of multiple copies of the N-myc oncogene with rapid progression of neuroblastomas. N Engl J Med 313:1111-1116, 1985
Seeger RC, Wada R, Brodeur GM, et al: Expression of N-myc by neuroblastomas with one or multiple copies of the oncogene. Prog Clin Biol Res 271:41-49, 1988
Crabbe DC, Peters J, Seeger RC: Rapid detection of MYCN gene amplification in neuroblastomas using the polymerase chain reaction. Diagn Mol Pathol 1:229-234, 1992
Shimada H, Chatten J, Newton WA Jr, et al: Histopathologic prognostic factors in neuroblastic tumors: Definition of subtypes of ganglioneuroblastoma and an age-linked classification of neuroblastomas. J Natl Cancer Inst 73:405-416, 1984
Chatten J, Shimada H, Sather HN, et al: Prognostic value of histopathology in advanced neuroblastoma: A report from the Childrens Cancer Study Group. Hum Pathol 19:1187-1198, 1988
Stram DO, Matthay KK, O'Leary M, et al: Myeloablative chemoradiotherapy versus continued chemotherapy for high risk neuroblastoma. Prog Clin Biol Res 385:287-291, 1994
Kaplan EL, Meier P: Nonparametric estimation from incomplete observations. J Am Stat Assoc 53:457-481, 1958
Look AT, Hayes FA, Shuster JJ, et al: Clinical relevance of tumor cell ploidy and N-myc gene amplification in childhood neuroblastoma: A Pediatric Oncology Group study. J Clin Oncol 9:581-591, 1991
Guo C, White PS, Hogarty MD, et al: Deletion of 11q23 is a frequent event in the evolution of MYCN single-copy high-risk neuroblastomas. Med Pediatr Oncol 35:544-546, 2000
Luttikhuis ME, Powell JE, Rees SA, et al: Neuroblastomas with chromosome 11q loss and single copy MYCN comprise a biologically distinct group of tumours with adverse prognosis. Br J Cancer 85:531-537, 2001
Breslow N, McCann B: Statistical estimation of prognosis for children with neuroblastoma. Cancer Res 31:2098-2103, 1971
Hartmann O, Valteau-Couanet D, Vassal G, et al: Prognostic factors in metastatic neuroblastoma in patients over 1 year of age treated with high-dose chemotherapy and stem cell transplantation: A multivariate analysis in 218 patients treated in a single institution. Bone Marrow Transplant 23:789-795, 1999
Stram DO, Matthay KK, O'Leary M, et al: Consolidation chemoradiotherapy and autologous bone marrow transplantation versus continued chemotherapy for metastatic neuroblastoma: A report of two concurrent Children's Cancer Group studies. J Clin Oncol 14:2417-2426, 1996
Shimada H, Umehara S, Monobe Y, et al: International neuroblastoma pathology classification for prognostic evaluation of patients with peripheral neuroblastic tumors: A report from the Children's Cancer Group. Cancer 92:2451-2461, 2001(Mary Lou Schmidt, Ashutos)