Extended pleurectomy decortication and chemotherapy versus chemotherapy alone for pleural mesothelioma (MARS 2): a phase 3 randomised controlled trial.

BACKGROUND: Extended pleurectomy decortication for complete macroscopic resection for pleural mesothelioma has never been evaluated in a randomised trial. The aim of this study was to compare outcomes after extended pleurectomy decortication plus chemotherapy versus chemotherapy alone. METHODS: MARS 2 was a phase 3, national, multicentre, open-label, parallel two-group, pragmatic, superiority randomised controlled trial conducted in the UK. The trial took place across 26 hospitals (21 recruiting only, one surgical only, and four recruiting and surgical). Following two cycles of chemotherapy, eligible participants with pleural mesothelioma were randomly assigned (1:1) to surgery and chemotherapy or chemotherapy alone using a secure web-based system. Individuals aged 16 years or older with resectable pleural mesothelioma and adequate organ and lung function were eligible for inclusion. Participants in the chemotherapy only group received two to four further cycles of chemotherapy, and participants in the surgery and chemotherapy group received pleurectomy decortication or extended pleurectomy decortication, followed by two to four further cycles of chemotherapy. It was not possible to mask allocation because the intervention was a major surgical procedure. The primary outcome was overall survival, defined as time from randomisation to death from any cause. Analyses were done on the intention-to-treat population for all outcomes, unless specified. This study is registered with ClinicalTrials.gov, NCT02040272, and is closed to new participants. FINDINGS: Between June 19, 2015, and Jan 21, 2021, of 1030 assessed for eligibility, 335 participants were randomly assigned (169 to surgery and chemotherapy, and 166 to chemotherapy alone). 291 (87%) participants were men and 44 (13%) women, and 288 (86%) were diagnosed with epithelioid mesothelioma. At a median follow-up of 22·4 months (IQR 11·3-30·8), median survival was shorter in the surgery and chemotherapy group (19·3 months [IQR 10·0-33·7]) than in the chemotherapy alone group (24·8 months [IQR 12·6-37·4]), and the difference in restricted mean survival time at 2 years was -1·9 months (95% CI -3·4 to -0·3, p=0·019). There were 318 serious adverse events (grade ≥3) in the surgery group and 169 in the chemotherapy group (incidence rate ratio 3·6 [95% CI 2·3 to 5·5], p<0·0001), with increased incidence of cardiac (30 vs 12; 3·01 [1·13 to 8·02]) and respiratory (84 vs 34; 2·62 [1·58 to 4·33]) disorders, infection (124 vs 53; 2·13 [1·36 to 3·33]), and additional surgical or medical procedures (15 vs eight; 2·41 [1·04 to 5·57]) in the surgery group. INTERPRETATION: Extended pleurectomy decortication was associated with worse survival to 2 years, and more serious adverse events for individuals with resectable pleural mesothelioma, compared with chemotherapy alone. FUNDING: National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (15/188/31), Cancer Research UK Feasibility Studies Project Grant (A15895).

Mesothelioma and Radical Surgery 2 (MARS 2): protocol for a multicentre randomised trial comparing (extended) pleurectomy decortication versus no (extended) pleurectomy decortication for patients with malignant pleural mesothelioma.

INTRODUCTION: Mesothelioma remains a lethal cancer. To date, systemic therapy with pemetrexed and a platinum drug remains the only licensed standard of care. As the median survival for patients with mesothelioma is 12.1 months, surgery is an important consideration to improve survival and/or quality of life. Currently, only two surgical trials have been performed which found that neither extensive (extra-pleural pneumonectomy) or limited (partial pleurectomy) surgery improved survival (although there was some evidence of improved quality of life). Therefore, clinicians are now looking to evaluate pleurectomy decortication, the only radical treatment option left. METHODS AND ANALYSIS: The MARS 2 study is a UK multicentre open parallel group randomised controlled trial comparing the effectiveness and cost-effectiveness of surgery-(extended) pleurectomy decortication-versus no surgery for the treatment of pleural mesothelioma. The study will test the hypothesis that surgery and chemotherapy is superior to chemotherapy alone with respect to overall survival. Secondary outcomes include health-related quality of life, progression-free survival, measures of safety (adverse events) and resource use to 2 years. The QuinteT Recruitment Intervention is integrated into the trial to optimise recruitment. ETHICS AND DISSEMINATION: Research ethics approval was granted by London - Camberwell St. Giles Research Ethics Committee (reference 13/LO/1481) on 7 November 2013. We will submit the results for publication in a peer-reviewed journal. TRIAL REGISTRATION NUMBERS: ISRCTN-ISRCTN44351742 and ClinicalTrials.gov-NCT02040272.