Extremity rhabdomyosarcoma in children, adolescents and young adults: A report from Children's Oncology Group trials.

Abstract

Long-term survival and prognostic factors for patients with extremity rhabdomyosarcoma (RMS) treated on contemporary Children's Oncology Group (COG) trials are unknown. Data of extremity RMS patients enrolled on COG trials from 1998 to 2014 were analyzed to estimate event-free survival (EFS) and overall survival (OS), and factors associated with survival. The authors identified 264 extremity RMS patients, 159 (60%) localized and 105 (40%) metastatic. The 5-year EFS and OS of patients with localized disease was 62.6% (54%, 71.2%), and 78.7% (71.4%, 85.9%) and of those with metastatic disease was 7.7% (2.2%, 13.2%) and 22.7% (13.9%, 31.4%). Age at diagnosis was associated with EFS, whereas both sex and age at diagnosis were associated with OS. In metastatic patients, a lower Oberlin score was associated with improved EFS and OS, and females had improved OS. The 5-year EFS of patients with localized disease treated on the D9803 trial was not statistically different from those treated on ARST0531, but 5-year OS was statistically superior (adjusted hazard ratio [adjHR] 0.43 [0.21, 0.86]) after adjusting for potential confounders. The 5-year EFS of group 3 patients undergoing delayed primary excision (DPE) with R0 margins was better than those with DPE with positive margins (adjHR 0.31 [0.11, 0.87]) and comparable to group 2 RMS patients. Outcomes for metastatic extremity RMS remain poor. Among patients with localized disease, younger age, female sex, and treatment on D9803 were associated with improved OS, whereas DPE with R0 margins led to better EFS compared to DPE with positive margins in group 3 patients.