Clinical benefit of methotrexate plus vinorelbine chemotherapy for desmoid fibromatosis (DF) and correlation of treatment response with MRI.

Background Desmoid fibromatosis (DF) is a rare fibroblastic proliferation that was historically treated with surgery. We report (a) outcomes using low-dose chemotherapy, methotrexate (MTX), and vinorelbine (VNL) for patients with progressing disease (PD) and (b) whether tumor volume (V-tumor) and T2 signal on magnetic resonance imaging (MRI) are more reflective of treatment response compared with maximum tumor dimension (D-max) defined by RECIST1.1. Methods Patients with biopsy-proven DF, treated with MTX/VNL from 1997 to 2015 were reviewed. MRI for a subset of patients was independently re-evaluated for response by RECIST, V-tumor, and quantitative T2 hyperintensity. Results Among 48 patients treated for a median 19 months MTX/VNL, only nine (19%) had previous surgery. RECIST-based overall response rate was complete response (CR) 20 (42%) + partial response (PR) 19 (39%), stable disease (SD) 8 (17%), for a clinical benefit rate of 98%. The median progression-free survival (PFS) was 120 months, (95%CI 84-155 months). Thirty-six (75%) patients had not progressed at a median 38 months from treatment completion. Most common grade 1/2 toxicities included nausea (n = 12, 25%) and fatigue (n = 9,19%) with no grade 3/4 toxicities. In 22 patients with serial MRIs, there was a decrease in D-max mean by 30%, V-tumor by 76%, and in 19/22 (86%) a decrease in T2 signal intensity. Conclusion Low-dose MTX/VNL for a defined duration has high efficacy with sustained benefit and minimal toxicity for treating DF. V-tumor and T2 signal might better predict treatment response than RECIST.