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/m²/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.