Efficacy and tolerability of sorafenib in desmoid-type fibromatosis: A need to review dose.

Background: Sorafenib is currently one of the recommended treatments for symptomatic patients with desmoid-type fibromatosis (DTF). In this study, we aim to assess the clinical efficacy and tolerability of sorafenib in DTF patients.

Methodology: Patients aged>18 years with a histological diagnosis of DTF and who have received sorafenib were enroled in this prospective observational study. Demographic data, clinical profile, the initial dose of sorafenib, treatment-related toxicities, dose modifications, and responses were recorded. The primary objective was to assess the objective response rate (ORR). The secondary objectives were to evaluate progression-free survival (PFS), tolerability, and adverse effects of sorafenib. Response assessment was based on response evaluation criteria in solid tumours 1.1 criteria. Adverse effects were graded according to National Cancer Institute Common Terminology Criteria for Adverse Events version 5.0 criteria. Time to event was calculated by Kaplan-Meier analysis, and survival was compared by log-rank test. Univariate and multivariable cox regression analysis were used to find independent predictors of relapse.

Results: A total of 104 patients were enroled in the study. The median age of the study population was 32 (range, 18-81) years, and 66.35% of patients were females. On response assessment, ORR was 46.1% and stable disease was observed in 31.7% patients. ORR was higher in the appendicular site (51.7%) compared to the abdominal site (27.2%). PFS at 1 and 2 years was 86.6% (79.6-92.7%) and 73.7% (62.4-82.8%), respectively. Two-thirds (66.6%) of patients had already received some form of treatment. At the time of analysis, 70 (67.3%) patients were continuing sorafenib. Only 4.8% stopped sorafenib due to progression, 10.5% due to intolerable adverse effects, and 17.3% due to other reasons. The common treatment-related toxicities were hand-foot skin reaction (HFSR) (89.4%), fatigue (79.8%), alopecia (70.1%), and diarrhoea (48.0%). In the patients with a starting dose of ≥400 mg (48.0% of patients), discontinuation was necessitated in 12% of patients, and further dose reduction was required in 58%, while only about 13% required dose reduction or discontinuation at a starting dose of 200 mg (51.9% of patients). Responses were not compromised due to lower starting doses.

Conclusions: Sorafenib has good activity in DTF, but it is associated with significant toxicity. The adverse effect profile is distinct in Indian patients with higher HFSR and alopecia. Due to the high rate of dose reduction/discontinuation with a starting dose of 400 mg, a starting dose of 200 mg may be recommended in Indian patients.