A randomized phase II trial of oral vinorelbine as second-line therapy for patients with malignant pleural mesothelioma.

8507 Background: All patients with malignant pleural mesothelioma (MPM) eventually relapse following standard chemotherapy. However, there is no standard treatment option in this setting. Vinorelbine, exhibits useful clinical activity but has not been formally evaluated in a randomised clinical trial, despite its widespread off-label use worldwide. BRCA1 regulates spindle assembly checkpoint in MPM and predicts vinorelbine sensitivity in preclinical models [1,2], suggesting that BRCA1 negative patients may be chemoresistant. Methods: VIM, a Cancer Research UK funded, investigator-initiated randomised controlled phase 2 multi-centre UK trial, enrolled patients with MPM who had progressed after first-line chemotherapy. Pts were randomised 2:1 to either vinorelbine (60mg/m2 weekly Q21d escalating to 80mg/m2 from cycle 2) + active supportive care (ASC) versus ASC until disease progression, unacceptable toxicity or withdrawal of consent. The primary outcome was progression free survival (PFS) defined as the time from randomisation to any progression (based on Modified RECIST criteria for assessment of response in malignant pleural mesothelioma) or death. The trial had 90% power to detect a hazard ratio of 0.65 at the one-sided 20% significance level. Secondary endpoints were overall survival (OS), tolerability and safety. Results: Between May 2016 and Oct 2018, 154 patients were recruited from 10 UK sites and randomised to vinorelbine + ASC (n=98) or ASC alone (n=56). In the Intention-to-treat analysis, after 129 events, median PFS was 4.2 months (m) for vinorelbine + ASC compared to 2.8m for ASC alone (Hazard Ratio (HR) 0.59; 95% CI: 0.41 to 0.85; one-sided p = 0.0017). 108 deaths were reported. Median OS was 9.3m for vinorelbine + ASC compared to 9.1m for ASC alone (HR=0.79; 95% CI: 0.53 to 1.17; two-sided p = 0.24). Toxicity data and subgroup analyses including the impact of BRCA1 deficiency will be presented. Conclusion: The trial met its primary endpoint. Vinorelbine demonstrates useful clinical efficacy in relapsed MPM, supporting its off-label use, as a treatment option for patients with relapsed MPM.[1] Busacca et al, J Pathol 2012, 227(2), 200. [2] Busacca et al, Mol Cancer Res, 2021, 20(2) 379. Clinical trial information: NCT02139904.