Systemic therapy for pre-treated malignant mesothelioma: A systematic review, meta-analysis and network meta-analysis of randomised controlled trials

Background: Randomised controlled trials (RCTs) with systemic therapies for patients with pre-treated mesothelioma have reported equivocal efficacy results and generated a degree of clinical uncertainty about the choice of active treatment in this poor prognosis malignancy. Methods: To compare the effectiveness and safety and weigh the benefit of different systemic treatments in patients with pre-treated mesothelioma by systematic review, meta-analysis and network meta-analysis of RCTs. Full-text articles and abstracts were searched on PubMed, EMBASE, Cochrane Library and oncology conferences proceedings from 2005 through November 2021 for phase 2 and 3 RCTs. The protocol was submitted to the PROSPERO registry. Reporting followed the PRISMA guideline. Outcomes of interest were overall survival (OS) and progression-free (PFS), grade ≥3 treatment-related (Tr) adverse events (AEs), Tr-deaths and Tr-AEs leading to treatment discontinuation. Findings: Nine trials at low risk of bias by Cochrane Collaboration's methodology were included, encompassing 2789 patients. Five studies showed PFS benefit in the experimental treatment. In two studies, OS was prolonged by immunotherapy (versus placebo) or by adding an antiangiogenic agent to chemotherapy. Reported Tr-AE were lower with single-agent anti-PD1 compared with chemotherapy or placebo. The meta-analysis revealed a beneficial global effect on OS and PFS from experimental treatments (HR 0.86, 95% CI 0.77-0.96, p = 0.0083 and HR 0.79, 95% CI 0.72-0.86, p < 0.001), that for the PFS significantly favoured the comparison with non-active treatments (HR 0.73, 95% CI 0.66-0.81, p < 0.001). Younger patients (i.e. <65-70 years) appeared to benefit the most in OS (HR 0.71, 95% CI 0.55-0.92, p = 0.04). The risk of serious Tr-AEs and Tr-deaths was not significantly increased by experimental treatments (RR 1.38, 95% CI 0.81-2.35, p = 0.24 and RR 2.07, 95% CI 0.69-6.24, p = 0.19, respectively) that instead increased TrAEs leading to treatment discontinuation (RR 2.9, 95% CI 1.44-6.08, p = 0.003). The network meta-analysis did not identify any superior treatment in PFS. Interpretation: For patients with pre-treated MPM, single-agent anti-PD1 or chemotherapy ± the antiangiogenic agent can be considered active and safe systemic therapeutic options, particularly for younger patients.