Efficacy and safety of combination PD-1/PD-L1 checkpoint inhibitors for malignant solid tumours: A systematic review.

Treatment of multiple malignant solid tumours with programmed death (PD)-1/PD ligand (PD-L) 1 inhibitors has been reported. However, the efficacy and immune adverse effects of combination therapies are controversial. This meta-analysis was performed with PubMed, Web of Science, Medline, EMBASE and Cochrane Library from their inception until January 2020. Random-effect model was adopted because of relatively high heterogeneity. We also calculated hazard ratio (HR) of progression-free survival (PFS), overall survival (OS) and risk ratio (RR) of adverse events (AEs), the incidence of grade 3-5 AEs by tumour subgroup, therapeutic schedules and therapy lines. Nineteen articles were selected using the search strategy for meta-analysis. Combined PD-1/PD-L1 inhibitors prolonged OS and PFS (HR 0.72, P < 0.001) and (HR 0.66, P < 0.001). In addition, incidence of all-grade and grade 3-5 AEs was not significant in the two subgroup analyses (HR 1.01, P = 0.31) and (HR 1.10, P = 0.07), respectively. Our meta-analysis indicated that combination therapy with PD-1/PD-L1 inhibitors had greater clinical benefits and adverse events were not increased significantly.