Efficacy and safety of adjuvant therapy with PD‑1/PD‑L1 inhibitors in cancer

Anti-programmed cell death protein-1 (PD-1)/programmed cell death 1 ligand 1 (PD-L1) antibodies have been widely used in cancers. The present study aimed to evaluate the efficacy and safety of PD-1/PD-L1 inhibitors in human cancers. Studies were searched from Cochrane Library, PubMed and Embase databases. Randomized controlled trials (RCTs) that investigated adjuvant therapy with anti-PD-1/PD-L1 agents in solid cancers were eligible for inclusion. As the primary focus of the meta-analysis, clinical outcome measures including overall survival (OS), disease-free survival (DFS), and adverse events (AEs) were analyzed by Stata 15.0 software. A total of six RCTs (n=4,436) met the inclusion criteria. The DFS [hazard ratio (HR)=0.71; 95% confidence interval (CI): 0.63-0.78; P<0.001] and OS (HR=0.66, 95% CI: 0.46-0.86, P<0.001) of patients were significantly prolonged by adjuvant immunotherapy. Subgroup analysis indicated that significantly improved DFS was observed in patients treated with different anti-PD-1/PD-L1 drugs (nivolumab, pembrolizumab, or atezolizumab), as well as in those with different tumors (melanoma, urothelial carcinoma, esophageal or gastroesophageal junction cancer, or renal cell carcinoma), and PD-L1 status [negative (<1%) or positive (≥1%)]. However, PD-1/PD-L1 inhibitors was associated with increased ≥ grade 3 treatment-related AEs (odds ratio=1.63; 95% CI: 1.20-2.21; P=0.002). The available evidence suggests that adjuvant therapy with PD-1/PD-L1 inhibitors provided more survival benefit than placebo for patients with cancer, with increased grade 3 or higher AEs. Prospero registration no. CRD42021290654.