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Journal of Clinical Oncology, Vol 24, No 24 (August 20), 2006: pp. 4043-4044 © 2006 American Society of Clinical Oncology. DOI: 10.1200/JCO.2006.07.1878
In ReplyDepartment of Hematology-Oncology, St Jude Children's Research Hospital, Memphis, Tennessee and Department of Pediatrics, University of Tennessee School of Medicine, Memphis, TN
Department of Pediatrics, Hospital for Sick Children, Toronto, Ontario, Canada We appreciate the lively debate that has taken place since the publication of our letter1 about the terminology used to describe pediatric soft tissue sarcomas (STS) other than rhabdomyosarcoma.2 In that letter, we argued that the term nonrhabdomyosarcoma STS describes these tumors better than the term adult-type STS because the distribution of STS histologic subtypes in children and adults is quite different. The use of the term adult-type STS also implies that children with these diseases should be treated as adults are treated. While we have learned much about the treatment of pediatric nonrhabdomyosarcoma soft tissue sarcomas (NRSTS) from adult STS clinical trials, we must remember that these studies include a different mix of diseases than are seen in pediatrics. Thus, the lessons learned from adult STS studies may not always translate perfectly to pediatric populations. In their letter, Ferrari and Casanova point out that differences in the distribution of STS subtypes in adults and children do not necessarily indicate that the underlying biology of adult and pediatric STS differs. While we have no doubt that this will be true for some STS subtypes, we expect that studies will uncover heterogeneity in other subtypes. Fibrosarcoma is a perfect example of age-associated differences in biology and clinical behavior. In older children and adults, fibrosarcoma behaves much like other high-grade STS, with unfavorable outcomes for patients with large or unresectable tumors. In infants, however, fibrosarcoma behaves in a much more benign fashion and is virtually always curable. The presence of the characteristic t(12;15) translocation defines infantile fibrosarcoma as a biologically distinct disease despite a microscopic appearance that is indistinguishable from adult-type fibrosarcoma.3 There are other examples of cancers whose biology and clinical behavior differ in pediatric and adult populations. Neuroblastoma, which virtually always occurs during childhood, typically has a more indolent course when it occurs in adults.4 Similarly, colorectal carcinoma, a tumor characteristic of adults, has a much poorer prognosis in pediatric patients, a finding that has been attributed to differences in the underlying tumor biology.5,6 Given the dearth of prospective data about children with NRSTS, we feel that it is premature to assume that these tumors are clinically and biologically identical to the same diseases that occur in adults. Even if pediatric and adult STS can be shown to be clinically and biologically identical, treatment considerations may differ according to patient age. For example, it may be perfectly reasonable to treat a 60-year-old adult with adjuvant radiotherapy after marginal resection of a low-grade STS. In a young child, such treatment might produce severe growth and functional impairment, in addition to many decades of risk for secondary neoplasia. Thus, it may be more prudent to avoid adjuvant radiotherapy in this setting and re-excise the tumor in the event of local recurrence. Despite the complexities inherent in these tumors, all pediatric and adult STS specialists can agree that more prospective studies are needed to better understand these diseases in both children and adults. Given the marginal benefit of standard chemotherapy in most STS and the poor outcomes of many of these patients, there is a critical need to identify novel therapies. Biology studies to identify important pathways and therapeutic targets will be key, as will histology-specific clinical trials. We agree with Ferrari that future progress in pediatric NRSTS depends on eliminating the obstacles preventing combined pediatric-adult STS studies. Differing treatment considerations may make collaborative pediatric-adult STS clinical trials challenging, but these issues should not be prohibitive. We look forward to joining Ferrari, Baker7, and others in designing future collaborative studies for adults and children with STS. Authors' Disclosures of Potential Conflicts of Interest The authors indicated no potential conflicts of interest. ACKNOWLEDGMENTS Supported in part by Grants No. CA 23099 and P30 CA 21765 from the National Institutes of Health and by the American Lebanese Syrian Associated Charities (ALSAC). REFERENCES
1. Spunt SL, Pappo AS: Childhood nonrhabdomyosarcoma soft tissue sarcomas are not adult-type tumors. J Clin Oncol 24:1958-1959, 2006 2. Ferrari A, Casanova M, Meazza C, et al: Adult-type soft tissue sarcomas in pediatric age: Experience at the Istituto Nazionale Tumori in Milan. J Clin Oncol 23:4021-4030, 2005 3. Knezevich SR, McFadden DE, Tao W, et al: A novel ETV6-NTRK3 gene fusion in congenital fibrosarcoma. Nat Genet 18:184-187, 1998[CrossRef][Medline] 4. Franks LM, Bollen A, Seeger RC, et al: Neuroblastoma in adults and adolescents: An indolent course with poor survival. Cancer 79:2028-2035, 1997[CrossRef][Medline] 5. LaQuaglia MP, Heller G, Filippa DA, et al: Prognostic factors and outcome in patients 21 years and under with colorectal carcinoma. J Pediatr Surg 27:1085-1089, 1992[CrossRef][Medline] 6. Hill D, Rao B, Cain A, et al: Colorectal carcinoma: A clinicopathologic review of 71 cases from St. Jude Children's Research Hospital. Proc Am Soc Clin Oncol 19:253a, 2000 (abst 983) 7. Baker LH: Medical and pediatric oncology, not adult and pediatric oncology. J Clin Oncol 23:4003-4005, 2005
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Copyright © 2006 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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