Radiation therapy in Wilms' tumor revisited.

Drs. Jeal and Jenkin in this issue review the abdominal irradiation experience of the Ontario Cancer Institute in Wilms’ tumor (WT) patients.‘* That institution has used total abdominal irradiation post operatively as a routine since 1960; al1 but one of 152 consecutive children with WT were treated in that fashion. Dose (2400 rad mean), daily fraction (100-125 rad) and field arrangements were more or less constant throughout that interval. Systemic adjuvant chemotherapy (CT) changed, however. First, no chemotherapy was given, then actinomycin D (AMD) alone was used in various dose combinations and more recently, maintenance AMD plus vincristine (VCR) has been employed. The authors sort these several factors in an analysis designed to establish whether chemotherapy has altered the frequency and patterns of abdominal relapse. Drs. Jeal and Jenkin conclude that the abdominal relapse rate in patients with early disease (Stages 1 and 11) is low in patients irradiated according to their system, and perhaps is lowest in those given both AMD and VCR. The numbers of children available for analyses in the various subsets were small, however, so that statistical significance could not be established. Reports of radiation therapy (RT) results obtained in single institutions such as this one can provide valuable information, especially when they include the era before effective CT was evolved. This is because the data help establish not only the criteria for patients who are at high risk, but also those who are at low risk for local relapse and in whom therapy can therefore safely be reduced. The issue is of particular importante in pediatrics, where the late deleterious consequences of therapy are of especial concern.3 These considerations properly have led investigators to repeated re-assessments of the role RT should play in the management of WT patients. Such a re-assessment is pertinent today in the light of the various prognostic factors that now are becoming better defined, and as the efficacy of CT becomes established in providing local as wel1 as systemic disease control.2.s.8 Discussions concerning RT in WT patients have been underway for decades, of course. The routine administration of postoperative irradiation of these children was credited with a major increase in survival experience by Gross and Neuhauser who first popularized the method.7 The statistical validity of their observation, which was based on smal1 numbers of patients, was questioned long ago by Schneider, who also suggested that patients with early disease might not require irradiation at all.” This proposal, which could be tested only in a large cooperative group study, was one of the therapeutic questions asked in the first National Wilms’ Tumor Study (NWTS-1).6 The outcome, as reviewed by Drs. Jeal and Jenkin, indicated that for children who also were given AMD for fifteen months, RT delivered postoperatively conferred no advantage to those under two years of age. Those over two given the same chemotherapy but no irradiation had more abdominal relapses than those who received RT. These results could not and. cannot be considered in a therapeutic vacuum, however.