Predictors of survival in alveolar rhabdomyosarcoma in the US.

Background: Alveolar rhabdomyosarcoma (ARMS) is an aggressive subtype of rhabdomyosarcoma with generally poorer outcomes than embryonal rhabdomyosarcoma. We analyzed a large contemporary cohort to characterize survival outcomes and prognostic factors for ARMS. Methods: We identified patients with histologically confirmed ARMS from the Surveillance, Epidemiology, and End Results (SEER) database. Demographics, tumor characteristics (stage, primary site), and treatments (surgery, radiation, and chemotherapy) were extracted. Cancer-specific survival (CSS) was estimated with Kaplan-Meier methods and compared using log-rank tests. Cox proportional hazards models were used for univariate and multivariate analysis of prognostic factors, with results reported as hazard ratios (HR) and 95% confidence intervals (CI). Results: A total of 592 ARMS patients were included [median age 14 years (interquartile range 7-25); 52% male; 73% White]. Primary tumors most commonly arose in extremities or trunk (64%), followed by head and neck sites (26%) and genitourinary locations (5%). Most patients received multimodal therapy: 44% underwent surgical resection, 70% received radiotherapy, and 92% received chemotherapy. The 5-year CSS for the entire cohort was approximately 43%. Distant metastasis was the strongest independent adverse prognostic factor (aHR: 2.9, 95% CI 2.13-3.92, Conclusions: In this large population-based study, ARMS survival remains poor, especially for patients with metastatic disease or in older age groups. Distant metastases and age ≥20 were associated with markedly inferior outcomes, while local therapy with surgery and radiation conferred significant survival benefit.