Outcome after pulmonary radiotherapy in Wilms' tumor patients with pulmonary metastases at diagnosis: a UK Children's Cancer Study Group, Wilms' Tumour Working Group Study.

PURPOSE: To evaluate the effect of whole lung radiotherapy on event-free and overall survival of children with Stage IV Wilms' tumor with pulmonary metastases at diagnosis and to ascertain factors that may have led to the decision to withhold radiotherapy. METHODS AND MATERIALS: We compared recurrence and mortality risks of patients with pulmonary metastases at diagnosis enrolled in the UKW2 and UKW3 clinical trials (1986-2001) according to treatment with pulmonary radiotherapy.
RESULTS: Of 102 eligible patients (43 patients in UKW2 and 59 patients in UKW3), 72 (71%) received pulmonary radiotherapy; 30 (29%) did not. After a median follow-up of 9.3 years (range, 0.6-14.1 years), event-free survival was 79.2% (95% confidence interval [CI], 67.8-86.9%) in patients who received pulmonary radiotherapy compared with 53.3% (95% CI, 34.3-69.1%) in patients who did not receive it (p = 0.006), with a hazard ratio of 2.66 (95% CI, 1.28-5.52; p = 0.009). There was no difference in overall survival (84.7% [95% CI, 74.1-91.2%] vs. 73.2% [95% CI, 53.4-85.6%], respectively; p = 0.157). Pulmonary radiotherapy reduced the chance of lung relapse (8.3% vs. 23.3%; p = 0.039). The omission of radiotherapy did not seem to be consistently associated with any specific clinical or radiologic features.
CONCLUSIONS: Outcome may be compromised if pulmonary radiotherapy is omitted in children with Wilms' tumor with pulmonary metastases. There was a significant effect on event-free survival; the risk of an event, particularly lung recurrence, was increased nearly threefold. Strategies for selection of children for avoidance of pulmonary irradiation need to be developed in a controlled fashion.