Delayed radiotherapy following dose intensive chemotherapy for parameningeal rhabdomyosarcoma (PM-RMS) of childhood

Purpose: To evaluate the local control rates and survival rates of patients with Group III parameningeal rhabdomyosarcoma (PM-RMS) treated with a dose intensive chemotherapy regimen followed by irradiation. Materials and methods: Twenty-six patients with group III, PM-RMS were enrolled in a prospective pilot trial at the Mayo Clinic, Rochester, MN and Children's Hospital and Regional Medical Center Seattle, WA. The median age at diagnosis was 8.5 years (range 1.5-19 years). The male to female patient ratio was 1.6:1. Twenty-three patients had embryonal histology with the remaining three alveolar. Risk factors indicating high risk disease included intracranial extension (10 patients), base of skull erosion (12 patients), and cranial nerve palsy (10 patients). The median follow-up period for all patients was 82 months (range 17-148 months). Patients were treated with an intensified chemotherapy regimen followed by definitive local irradiation at week 12 following further chemotherapy. The median time from initiation of chemotherapy to irradiation was 16 weeks (range 6-23). The median dose delivered was 50.4 Gy (50.4-66.6 Gy). Results: Response was assessed after the fourth course of chemotherapy. Three patients exhibited a complete response, 22 a partial response, and 1 patient had no response after two cycles of chemotherapy and proceeded to irradiation at week 6. The 5-year estimated event free survival was 81% (±15%, 95% CI). Two patients died from progressive metastatic disease; 1 patient died from secondary malignancy; and 2 patients died from locally progressive disease. The 5-year local control rate was 92% (±10.6%, 95% CI). Conclusions: Treatment of group III PM-RMS patients with neo-adjuvant, intensive chemotherapy with a delay in irradiation resulted in excellent local-regional control rates and survival rates and may allow for a response-based radiotherapy approach.