Perianal/perineal rhabdomyosarcoma: Results of the SIOP MMT 95, Italian RMS 96, and EpSSG RMS 2005 studies

Abstract Background/objectives Rhabdomyosarcoma of the perianal/perineal region (PRMS) is rare, with poor survival and limited understanding of the functional consequences of treatment. Design/methods International Society of Pediatric Oncology (SIOP) malignant mesenchymal tumor (MMT) 95, Italian RMS 96, and European paediatric Soft tissue sarcoma Study Group (EpSSG) RMS 2005 studies were interrogated to identify factors that impact survival; in RMS 2005, functional outcomes were analyzed. Results Fifty patients (nonmetastatic) were identified, median age 6.4 years (range: 0.1–19.6): 29 male, 21 female. Tumors were >5 cm in 33 patients. Histopathological subtype was alveolar in 35. Lymph nodes were involved in 23 patients. In RMS 2005, 16/21 (76%) tested alveolar tumors had positive FOXO1 fusion status. Diagnostic biopsy was performed in 37. Primary resection (13) was complete (R0) in one. Delayed primary excision (16) was complete in three. Radiotherapy (RT) in 34/50 patients included external beam (28), brachytherapy (3), and both (3). Nodal RT was given in 16/23 N1 patients (70%). Median follow‐up of alive patients (29) was 84.1 months (range: 3.6–221.1). Relapse or progression occurred in 24 patients (48%), 87% were fatal and most events (63%) were locoregional. Five‐year event‐free survival (EFS) was 47.8 (95% CI: 32.8–61.3), and 5‐year overall survival (OS) was 52.6 (95% CI: 36.7–66.2), with age ≥10 years and tumor size >5 cm impacting 5‐year EFS and OS ( p < .05). Functional outcome data showed bowel, genito‐urinary, and psychological issues; fecal incontinence in four of 21 survivors, and urinary symptoms in two of 21. Conclusions About 60% of patients with nonmetastatic PRMS survive; older patients and those with large tumors have the worst outcomes. Biopsy should be the initial procedure, and definitive local therapy individualized. Quality‐of‐life and functional studies are needed to better understand the consequences of treatment.