Intraoperative spillage of favorable histology wilms tumor cells: influence of irradiation and chemotherapy regimens on abdominal recurrence. A report from the National Wilms Tumor Study Group.

PURPOSE We undertook this study to determine (1) the frequency with which spilled tumor cells of favorable histology produced intra-abdominal disease in patients treated with differing chemotherapy regimens and abdominal radiation therapy (RT) and (2) the patterns of relapse and outcomes in such patients. METHODS AND MATERIALS The influence of RT dose (0, 10, and 20 Gy), RT fields (flank, whole abdomen), and chemotherapy with dactinomycin and vincristine (2 drugs) vs. added doxorubicin (three drugs) on intra-abdominal tumor recurrence rates was analyzed by logistic regression in 450 patients. Each patient was considered at risk for two types of failure: flank and subdiaphragmatic beyond-flank recurrence, with the correlation between the two outcomes accounted for in the analyses. RESULTS The crude odds ratio for the risk of recurrence relative to no RT was 0.35 (0.15-0.78) for 10Gy and 0.08 (0.01-0.58) for 20Gy. The odds ratio for the risk of recurrence for doxorubicin to two drugs after adjusting for RT was not significant. For Stage II patients (NWTS-4), the 8-year event rates with and without spillage, respectively, were 79% and 87% for relapse-free survival (p = 0.07) and 90% and 95% for overall survival (p = 0.04). CONCLUSIONS Irradiation (10 Gy or 20 Gy) reduced abdominal tumor recurrence rates after tumor spillage. Tumor spillage in Stage II patients reduced relapse-free survival and overall survival, but only the latter was of statistical significance. These data provide a basis for assessing the risks vs. benefits when considering treatment for children with favorable histology Wilms tumor and surgical spillage.