Immune checkpoint inhibitors (ICIs) have drastically changed the clinical care of cancer. Although cancer immunotherapy has shown promise in various types of malignancies, thus far, the proportion of patients who can benefit from ICIs is relatively small. Immune-related adverse events and high cost are unavoidable problems. Therefore, biomarkers defining patients that are most likely to benefit from ICIs are urgently needed. The expression of programmed cell death-ligand 1 (PD-L1) is a logical biomarker for the prediction of response to anti-PD1/PD-L1 immunotherapies. However, its usefulness is currently debatable because of its varied definition, threshold, and spatial/temporal heterogeneity. Recently, it was reported that the tumor mutational burden, expression of neoantigens, mismatch repair status, and specific gene mutations may be markers for the success of treatment with ICIs. Moreover, it was suggested that the fecal microbiota prior to immunotherapy may play an important role in predicting the efficacy of ICIs. In this review, we focused on these potential biomarkers for cancer immunotherapy reported in recent clinical articles. Further studies are warranted to develop a predictive model using these biomarkers, with the aim of practicing precision medicine in cancer immunotherapy.

Aim: The aim of the present study was to assess the prognostic utility of the pretreatment blood neutrophil-to-lymphocyte ratio (NLR) and the C-reactive protein-to-albumin ratio (CAR) in patients with inoperable malignant pleural mesothelioma (MPM). Materials and Methods: The medical records of consecutive patients with histologically confirmed MPM from our hospital between January 2007 and August 2017 were retrospectively reviewed. The primary outcome was overall survival (OS). Univariate and multivariate analyses for the prognostic factors were performed using a Cox proportional hazards model. Results: A total of 143 patients with inoperable MPM were included. On multivariate analysis, pretreatment CAR was an independent factor associated with worse OS (hazard ratio(HR)=1.72; 95% confidence interval(CI)=1.11-2.67; p=0.016). However, NLR was not associated with OS in any of the analyses. Conclusion: CAR appears to be a prognostic factor in patients with inoperable MPM.