Background: Immune checkpoint inhibitors, which are a milestone in anti-cancer therapy, have been applied in the treatment of multiple malignancies. Real-world data have suggested that smoking status may be associated with the efficacy of anti-PD-1/PD-L1 therapy. Hereby, to evaluate "smoking benefit or not", we included numerous high-quality randomized controlled clinical trials (RCTs) without any restriction on category.
Methods: A systematic search of online database was performed from July 2010 to July 2019. Eligible studies included phase II/III RCTs comparing PD-1/PD-L1 inhibitors with chemotherapy in the treatment of multiple carcinomas and contained subgroup analysis of smoking status. Then, related hazard ratios (HRs) with 95% confidence intervals (CIs) of overall survival (OS) were pooled.
Results: In the initial meta-analysis, compared with chemotherapy, the OS of non-smokers (HR, 0.81; 95% CI, 0.67-0.98) and smokers (HR, 0.77; 95% CI, 0.71-0.83) were significantly prolonged with PD-1/PD-L1 inhibitors. Outcomes from subgroup analysis showed that in anti-PD-1/PD-L1 monotherapy groups, non-smokers showed no significant improvement in OS (HR, 0.94; 95% CI, 0.83-1.06), while the OS of smokers was significantly prolonged (HR, 0.79; 95% CI, 0.74-0.85); in groups of PD-1/PD-L1 inhibitors combined with chemotherapy, the OS of non-smokers (HR, 0.45; 95% CI, 0.28-0.71) and smokers (HR, 0.72; 95% CI, 0.61-0.85) were significantly prolonged. Combined ipilimumab and chemotherapy showed no significance in both groups.
Conclusion: Smokers benefit from either anti-PD-1/PD-L1 monotherapy or the combined regimen compared with chemotherapy. Considering cost-effectiveness, monotherapy was recommended to smokers. For non-smokers, only the combined regimen was feasible in non-small cell lung cancer.
Keywords: Anti-PD-1/PD-L1; Immune checkpoint inhibitors; Immunotherapy; Meta-analysis; Smoking.