Development Of Thrombocytopenia Is Associated With Improved Survival In Patients Treated With Immunotherapy

Background: Immune-related adverse events are associated with efficacy of immune checkpoint inhibitors (ICIs). We hypothesize that immune-mediated thrombocytopenia could be a biomarker for response to ICIs. Materials & methods: This retrospective study included 215 patients with metastatic malignancies treated with ICIs. Patients were stratified by nadir platelet count. Outcomes of interest were progression-free survival and overall survival. Results: On multivariate analysis, grade 1 thrombocytopenia was positively associated with overall survival compared with patients who did not develop thrombocytopenia (hazard ratio [HR]= 0.28 [95% CI: 0.13-0.60]; p = 0.001), while grade 2-4 thrombocytopenia was not (HR= 0.36 [95% CI: 0.13-1.04]; p = 0.060). There was no association between degree of thrombocytopenia and progression-free survival. Conclusion: Follow-up studies are warranted to substantiate the predictive significance of thrombocytopenia in patients receiving ICIs. Lay abstract: Immune checkpoint inhibitors (ICIs) are a class of drug that are increasingly being used in different cancers. The extent of response to treatment with ICIs differs among individuals. There is a lack of biomarkers, which would help clinicians predict response to ICIs. In our study, we aimed to explore the development of low platelets as a potential biomarker. Our findings suggest that cancer patients receiving ICIs who develop a mild decrease in platelet count tend to live longer than those who do not. However, this was not true for those who developed a severe decrease in platelet count. The mechanism of how ICIs affect platelets may be related to the interaction between the immune system and platelets. More studies are needed to validate our results and better understand the role of platelets in cancer biology.