Radiation therapy of Wilms' tumor: Results according to dose, field, post-operative timing and histology

Abstract

Abstract The results were reviewed after radiation therapy (RT) and systemic chemotherapy in 250 patients enrolled in the National Wilms' Tumor Study (NWTS). Factors considered were delay in initiating post-operative RT, dose delivered, field sizes employed, and the histology tumor grade. Good local control was observed; only 5 patients had recurrent disease confined to the operative bed. Delays of up to nine days were not associated with adverse results. The field sizes employed, most often designed to include the tumor bed and the adjacent para-aortic lymph nodes, appeared to have provided adequate coverage. Relapse-free survival rates and rad doses in the range used were not correlated; doses greater than 2400 rad (1000 rad/week) did not yield better results. Lower doses, e.g. 1800–2000 rad appeared satisfactory in infants under 13 months of age. Histologic grade was a potent prognostic indicator. Patients with anaplastic tumors and those with sarcomatous features have high relapse and mortality rates. The NWTS already has shown that children under 2 years of age with localized tumors that are totally removed, and who receive systemic single agent chemotherapy, gain no advantage from post-operative RT. Two-year survival rates for these irradiated and non-irradiated children were 9796 and 9496 respectively. However, fewer infradiaphragmatic relapses and fewer deaths were recorded in their older irradiated counterparts when compared with those 2 years old or more not given RT. No such difference is apparent in 97 non-irradiated patients of all ages with early disease followed for at least 1 year in the second NWTS, all of whom were given double agent chemotherapy. These observations, together with the results of this review, which do not show a distinct correlation between RT parameters and outcome, call for re-examination of the role of post-operative irradiation in the modern management of Wilms' tumor patients.