Vinblastine and methotrexate for desmoid fibromatosis in children: Results of a Pediatric Oncology Group phase II trial

Purpose To determine the efficacy and safety of using vinblastine (Vbl) and methotrexate (Mtx) in children with desmoid-type fibromatosis that is recurrent or not amenable to treatment with radiation or surgery. Patients and Methods A phase II study was conducted within the Pediatric Oncology Group. Patients were treated using Vbl ( 5 mg/m(2)/dose) and Mtx ( 30 mg/m(2)/dose), both administered by intravenous injection weekly for 26 weeks and every other week for an additional 26 weeks. Response was assessed by bidimensional measurements of tumor on axial imaging ( magnetic resonance imaging or computed tomography). Results Over 35 months, 28 patients were enrolled; 27 were eligible, and 26 were assessable for response. A measurable response was documented in eight patients (31%), and 10 patients had stable disease documented as the best response to treatment. Eighteen patients had disease progression at a median time of 9.1 months. Eight patients remain free of disease progression at a median of 43.4 months from study entry. Nine patients reported no to moderate toxicity. Neutropenia was the most common toxicity ( n = 22) and the most common grade 4 toxicity ( n = 5). Anemia, nausea, vomiting, and elevations in hepatic transaminases were also common and were reversible with interruption of chemotherapy. Conclusion Vbl and Mtx are well tolerated in children with desmoid-type fibromatosis. Furthermore, this combination can promote tumor regression or block tumor growth in most children.