Evaluation of the prognostic role of platelet-lymphocyte ratio in cancer patients treated with immune checkpoint inhibitors: A systematic review and meta-analysis

Objective: Whether platelet-lymphocyte ratio (PLR) is a prognostic factor for cancer patients treated with immunotherapy is under debate. In this study, we aimed to evaluate the relationship between PLR and survival of cancer patients treated with immune checkpoint inhibitors (ICIs). Methods: A systematical search was performed in databases including PubMed, Embase, and the Cochrane library to retrieve potential eligible clinical studies assessing the prognosis of cancer patients with high versus low PLR after immunotherapy, from the establishment of the database to June 2019. Quality evaluation of included studies was performed, and meta-analyses with regards to overall survival (OS) and progression-free survival (PFS) were conducted using RevMan 5.3 and STATA 11. Results: A total of 12 eligible studies with 1340 cancer patients were included. Combined results showed that elevated PLR was a negative factor affecting the efficacy of ICIs in cancer patients. Patients with high PLR had a significantly shorter OS compared to those with low PLR (hazard ratio (HR) = 2.02, 95% confidence interval (CI): 1.46 to 2.80, P < 0.0001), as well as PFS (HR = L74, 95%CI: 1.27 to 2.38, P = 0.0006). Similar results were observed in sensitivity analyses. Subgroup analyses revealed that the prognostic role of PLR on OS and PFS was dependent on cancer type, region, and cutoff value. For NSCLC patients, the disease stage, ICIs agent, and line of treatment may not influence the prognostic role of PLR. Conclusion: PLR could be a routinely potential prognostic factor for ICIs. Low PLR may be associated with better survival for cancer patients when treated with immunotherapy.