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Journal of Clinical Oncology, Vol 25, No 6 (February 20), 2007: pp. 737 © 2007 American Society of Clinical Oncology. DOI: 10.1200/JCO.2006.06.4915
Predictive Value of Staging Systems in HepatoblastomaDivision of Pediatric Surgery, Primary Children's Medical Center, University of Utah, Salt Lake City, UT
Pediatric Hematology, Oncology, Children's Healthcare of Atlanta, Emory University, Atlanta, GA
Division of Pediatric Hematology, Oncology, Children's Hospital of Los Angeles, University of Southern California, Los Angeles, CA To the Editor: We read with great interest the article by Aronson et al "Predictive Value of the Pretreatment Extent of Disease System in Hepatoblastoma: Results from the International Society of Pediatric Oncology Liver Tumor Study Group SIOPEL-1 Study."1 This article describes the accuracy, reproducibility, and predictive value of the liver tumor Pretreatment Extent of Disease (PRETEXT) staging system from the International Society of Pediatric Oncology Liver Tumor Study Group (SIOPEL-1). In particular we would like to highlight and applaud the authors' observation that the PRETEXT system offers the opportunity to monitor the effect of preoperative chemotherapy and to assess both the surgical resectability of the tumor and the required type of resection before surgery. This system clearly has added a great deal to the nomenclature of critical analysis of hepatoblastoma. Yet, in the remainder of this letter we would like to point out that the methodology used to compare the predictive value of the PRETEXT system with the predictive value of two alternative hepatoblastoma staging systems ultimately leads them to a curious, almost nonsensical, result. Aronson et al1 compare the PRETEXT system used by the European-based SIOPEL group retrospective manner with two alternative systems: the system used by the American-based Children's Oncology Group (COG; formerly the Children's Cancer Study Group/Pediatric Oncology Group [CCSG/POG]) and the conventional TNM system, previously used by the German cooperative hepatoblastoma trials. They conclude that the "predictive value for survival of PRETEXT and of the tumor-node-metastasis–based system was highly significant in contrast to the predictive value of the CCSG/POG/COG-based system which was poor."1 We question this conclusion because the way in which the COG system was applied to their data set is not a valid application of the American COG staging system. The COG staging system was designed to assign tumor stage at the time of diagnosis. Surgery is performed in all patients at diagnosis either as an incisional biopsy or an attempted definitive resection. The stage is assigned according to the extent of this surgery at diagnosis. It is especially important to note that the stage is assigned before any neoadjuvant chemotherapy has been given and includes a risk stratification with respect to the presence or absence of metastatic disease at diagnosis. In the article by Aronson et al the COG stages were inappropriately applied to the data set after neoadjuvant chemotherapy had been given, and most important, after patients who were chemotherapy nonresponders had been excluded from analysis. Exclusion of this entire cohort of chemotherapy nonresponders lead to the curious result. The authors gently acknowledge this flaw in their closing statement by saying that further research is necessary to evaluate the predictive value of PRETEXT "not only in patients who receive surgical resection, but in all patients."1 Perhaps it is best to let the numbers speak for themselves. We thought it would be interesting to take the methodology used in the article by Aronson et al and apply it retrospectively to an American hepatoblastoma data set obtained in the COG cooperative study Intergroup (INT)-0098,2 an American trial contemporary to SIOPEL-1. The INT-0098 stage IV patients provide the most vivid example of selective methodology by Aronson et al. INT-0098 enrolled 41 stage IV patients. Eight patients underwent definitive surgical resection of the primary tumor at diagnosis, but only two were long-term survivors. There were 15 patients who had surgical biopsy at diagnosis and were not responsive to chemotherapy with progressive disease and early death. Of the 18 patients who successfully completed neoadjuvant chemotherapy and went on to definitive surgical resection, survival was 72%. This is not a true reflection of the overall survival rate of 36% in the group as a whole. Whether or not you agree with the COG staging system, it is not a genuine reflection of its predictive capability to retrospectively analyze a select subset of patients. We agree with the authors that PRETEXT is a wonderful tool for predicting resectability and even survival in the subgroup of patients who successfully complete neoadjuvant chemotherapy. This article, however, did not include patients who failed neoadjuvant chemotherapy and points out that PRETEXT is not a risk stratification tool that can be used in isolation without other high-risk predictors, such as metastatic disease and tumor histology. Buried in the Discussion of Aronson et al is a token nod given to this fundamental flaw. Yet we believe that this critical detail fatally undercuts the bold statement in the abstract of the article, which states, "The CCSG/POG-based staging system showed no predictive value for survival." The statement could more accurately read, "shows no predictive value for survival in the retrospective, select subset of patients we chose to analyze in this article." We would like to remind the readers that the COG system was not designed with a subset of patients in mind, but with all patients in mind. AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST The authors indicated no potential conflicts of interest. REFERENCES
1. Aronson DC, Schnater JM, Staalman CR, et al: Predictive value of the pretreatment extent of disease system in hepatoblastoma: Results from the International Society of Pediatric Oncology Liver Tumor study group SIOPEL-1 study. J Clin Oncol 23:1245-1252, 2005 2. Ortega JA, Douglass EC, Feusner JH, et al: Randomized comparison of cisplatin/vincristine/fluorouracil and cisplatin/continuous infusion doxorubicin for treatment of pediatric hepatoblastoma: A report from the Children's Cancer Group and the Pediatric Oncology Group. J Clin Oncol 14:2665-2675, 2000
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Copyright © 2007 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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