Outcomes Following Proton Therapy for Group III Pelvic Rhabdomyosarcoma

This study aimed to report on the institutional outcomes after proton therapy for pelvic rhabdomyosarcoma (RMS). Thirty-one children (≤21 years old) with group III pelvic RMS were enrolled on a prospective outcome study and treated between 2007 and 2018. Patients with vaginal/cervical RMS were excluded. The median age was 2.6 years. Twenty-four patients had embryonal RMS. At diagnosis, the median tumor volume was 185 cm3 and the median maximum diameter was 9.4 cm. Seven patients had N1 disease. Nineteen and 12 patients received European Pediatric Soft Tissue Sarcoma Study Group– and Children’s Oncology Group–based chemotherapy, respectively. Fourteen patients underwent resection of the primary tumor after induction chemotherapy, including 6 patients who had a total cystectomy. The median radiation dose was 50.4 Gy relative biological effectiveness. With a median follow-up of 4.2 years, the 5-year local control, progression-free survival, and overall survival rates were 83%, 80%, and 84%, respectively. Patients