Outcome for Clinical Group III Rhabdomyosarcoma Patients Who Did Not Receive Radiotherapy on IRS-III and -IV

Purpose/Objective: To assess the outcome of patients in whom radiotherapy (RT) was not given, in order to determine if any patient subset might have omission of RT tested in future clinical trials. Materials/Methods: Seventy-two patients who remained on study and did not fail up to the time when RT would have begun were analyzed. Among these 72, RT omission was allowed per protocol in 24 who had second-look surgery (SLS) (20 with non-bladder/prostate (B/P) GU primaries, one with bladder dome, and three amputees with extremity primaries); these patients were included in this analysis. 904 CG III patients on IRS-III and -IV who did receive RT are reported for comparison but without tests of statistical significance. Primary endpoints were five-year total local failure (LF), failure-free survival (FFS), and overall survival (OS). Results: LF was not different overall (18% v 16%). However, non-B/P GU patients were infrequent in the RT cohort (3%) but comprised 46% (33/72) of the no RT cohort, and their relatively low LF skewed the overall LF rate. Examining each site group separately revealed apparently worse LF without RT, whereas FFS and OS were better in the no RT cohort for all site groups except those with other/PM/orbit/H&N primaries (TABLE). In the RT group, the effect of age (under 1 yr v 1 yr or older) was examined separately for GU and for all others. For GU patients, LF was 28% v 8%, FFS was 71% v 91%, and OS was 86% v 100%. For all others, LF 62% v 12%, FFS 37% v 66%, and OS 63% v 70%. Second-look surgery in the no RT group consisted of radical procedures (total or subtotal sacrifice of at least one organ, resulting in irreversible loss of function) in 21/72 (including 9 cystectomies, 8 hysterectomies, 6 vaginectomies, and 3 extremity amputations), resection in 22, biopsy in 16, and unknown in 6. No SLS was performed in 7 patients. Conclusions: Omission of RT in favor of SLS or no local therapy resulted in local failure rates higher than would be predicted for all primary sites. Radical surgery was used in 21/72 patients. Age under 1 year was also predictive of higher local failure risk. Nevertheless, overall survival in this highly selected population was not compromised, especially in non-B/P GU patients. The clinical features to permit RT omission cannot be fully determined in this analysis, supporting the current guidelines for SLS and RT dose reduction as recommended in IRS V. Tabled 1