Efficacy & safety of oral vinorelbine in desmoid fibromatosis

Summary

Introduction: Desmoid-type fibromatosis (DF) are a group of rare (0.03% of total neoplasms) benign tumours arising from fibroblasts that can exhibit locally aggressive behaviour.1 Single agent oral vinorelbine (90 mg weekly for three consecutive weeks of each 28-day cycle) recently emerged as a simplified, less toxic and more manageable alternative to the standard pharmacological approach with two-weekly IV methotrexate and vinorelbine in patients with aggressive or refractory disease.2,3 This study aimed at describing the efficacy and safety of oral vinorelbine in a cohort of patients with DF in any line of treatment. Methods: This was a single-centre, retrospective study of patients treated with oral vinorelbine for DF over a period of 18 months (Jan 2020 to Jun 2021) within a specialised cancer centre. Patients who received at least 3 cycles of treatment (or until the first documented radiographic assessment, whatever occurred first) were included. The following information was collected from the electronic health care records system (Epic®) patient demographics (age, gender), number of previous treatment lines, and number of number of months on treatment (until closure of observations). Efficacy clinical and radiographic reports were used to determine disease status as per RECIST A subgroup analysis of patients who were transitioned from other pharmacological options was also performed. Safety routine full blood count and biochemistry weekly for the first three cycles, and once monthly thereafter were assessed for blood dyscrasias. Other side effects were also recorded. Results: Twenty-four patients were initially started on oral vinorelbine, of which 19 met the inclusion criteria (baseline and demographic characteristics summarised in table 1). Efficacy Symptomatic improvement was observed in all cases (100%) shortly after initiation. Favourable radiographic findings (SD or better) were documented in 18 cases (94.73%). Only one patient (5.26%) experienced marginal increase in tumour size, but was maintained on treatment until further assessment, as still deriving clinical benefit. Additionally, all subjects in the subgroup who were transitioned from other pharmacologic options (9 patients) showed disease response. Safety one episode of grade 3 neutropenia observed after seven cycles. Full blood counts and biochemistry parameters remained otherwise stable throughout treatment one patient had low haemoglobin requiring multiple blood transfusions;this occurred in the context of poor baseline renal function and remained essentially unchanged throughout. The main reported toxicities were diarrhoea (5 cases), nausea (grade 1 in 7 patients and grade 2 in one), fatigue (8), constipation (grade 2, 4 patients), and headaches and muscle pain (one case each). Discussion/ conclusion: Single agent oral vinorelbine was found to be an effective treatment option for the management of newly diagnosed or refractory DF;this was also true for a subgroup of patients who received this to reduce hospital visits or after failure of a previous treatment line. Safety-wise, patients had stable blood counts and biochemical values throughout treatment, whereas most toxicities were mild and did not require discontinuation. These findings are in line with previous reports and underpin a paradigm shift in the management of DF in the post-COVID era.