Changes of Immune Cell Fractions in Patients Treated with Immune Checkpoint Inhibitors

Simple Summary Immune checkpoint inhibitors (ICIs) are currently widely used in many types of cancer. However, some patients could not benefit from ICIs. In addition, a standardized biomarker for predicting the efficacy of ICIs is currently unavailable. Thus, we determined whether peripheral blood immune cells could be predicting markers. In contrast with previous studies, we focused on changes in immune cell fraction and the relationship between efficacy of ICIs including response rate and survival outcomes. Results revealed significant correlations between changes in NKp46-/CD56+ NK cell fraction and treatment outcomes with ICIs. Background: With the development of immunology, immune checkpoint inhibitors (ICIs) have been widely used in various cancer treatments. Although some patients can benefit from ICIs, other patients have no response to ICIs or suffer from hyperprogression. There has been no biomarker for predicting the efficacy of ICIs. Thus, the objective of this study was to find biomarkers for predicting the efficacy of ICIs using peripheral blood. Methods: Adults patients planned to be treated with ICIs were enrolled in this study. Blood sampling was carried out before and after administration of ICIs. Changes of immune cell fraction were analyzed for each patient. Results: Among 182 patients enrolled, immune cell analysis was performed for 90 patients. The objective response rate was 14.4% (n = 13/90). The median progression-free survival (PFS) was 6.0 months (95% CI: 3.1-8.9 months), and the median overall survival (OS) was 13.9 months (95% CI: 5.6-22.2 months). Significant benefits in ORR and OS were shown for patients with increased NKp46-/CD56+ NK cells (p = 0.033 and p = 0.013, respectively). The PFS tended to be longer in these patients, although the difference was not statistically significant (p = 0.050). Conclusion: Changes of immune cell fraction before and after administration of ICIs could be a novel biomarker for predicting the efficacy of immunotherapy.