Impact of Rhabdomyosarcoma Treatment Modalities by Age in a Population-Based Setting.

Purpose: Rhabdomyosarcoma (RMS) has a worse prognosis in adults than in children, but there is evidence of a better outcome in the former if treated using a pediatric-like approach. This study describes treatment for RMS in patients more than 10 years old and examines to what extent treatment contributes to explain the different age-related survival observed and to what extent treatment centers impact treatment appropriateness. Methods: A retrospective population-based study was developed considering 104 RMS cases (excluding the pleomorphic subtype) diagnosed in Italy between 2000 and 2015. Patients were grouped by age (10–19 vs. 20–60 years old) and scored according to whether or not their chemotherapy was consistent with the schemes used in pediatric protocols (score 1 = chemotherapy in line with pediatric protocols). Treatment centers were grouped according to whether or not they have a pediatric-dedicated unit affiliated to the national pediatric oncology network (Associazione Italiana Ematologia Oncologia Pediatrica [AIEOP]). Results: Older patients were more likely to have tumors at unfavorable sites (p = 0.045). A treatment score of 1 was assigned to 85% of younger patients, but only to 32% of older patients (p < 0.001). Furthermore, the proportion of score 1 was higher in younger patients treated in centers with an AIEOP Unit. A multivariate model confirmed age as a significant prognostic factor (Hazard rate ratio [HR] = 2.06; p = 0.04) and showed a significant impact of treatment on survival (HR = 2.13; p = 0.03). Conclusions: Adult RMS patients are still relatively unlikely to be treated with pediatric protocols and in centers with a pediatric oncology expertise. This may explain the survival gap between older and younger patients. [ABSTRACT FROM AUTHOR]