Predictors of survival in alveolar rhabdomyosarcoma in the US

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.

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).

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, P < 0.001), and regional nodal involvement also independently worsened CSS (aHR: 1.46, 95% CI 1.07-1.99, P = 0.016) compared to localized disease. Older age (≥20) at diagnosis was associated with higher mortality risk (aHR: 1.82 vs. age <10, P < 0.001). Notably, the use of surgery (aHR: 0.74, P = 0.031) and radiation therapy (aHR: 0.62, P < 0.001) were independently associated with improved CSS after controlling for stage and age.

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.