Shorter duration therapy that includes vincristine (V), dactinomycin (A), and lower doses of cyclophosphamide (C) with or without radiation therapy for patients with newly diagnosed low-risk embryonal rhabdomyosarcoma (ERMS): A report from the Children’s Oncology Group (COG).

9516 Background: Intergroup Rhabdomyosarcoma Study (IRS) trials showed excellent survival with VA or VAC for patients with Stage 1 or 2, Group I or II ERMS or with Stage 1, Group III orbit ERMS. In COG ARST0331, we hypothesized that VA in combination with lower doses of C (total cumulative dose = 4.8 g/m2) would produce the benefit of IRS-IV VAC with less toxicity and that length of therapy could be reduced without compromising failure free survival (FFS) of patients with low-risk ERMS. Methods: This single arm, noninferiority, phase III study enrolled newly diagnosed patients with Stage 1 or 2, Group I or II ERMS or patients with Stage 1, Group III orbit ERMS onto Subset 1. Therapy was 4 cycles of VAC followed by 4 cycles of VA over 22 weeks (total cumulative doses: V=27 mg/m2, A=12 mg/m2, C=4.8 g/m2). The radiation therapy dose was 36 Gy for Group IIA patients, 41.4 Gy for Group IIB/C patients, and 45 Gy for Group III orbit patients. The primary endpoint was FFS, and results were compared with a fixed e...