Pre-Treatment Peripheral Blood Parameters as Prognostic Biomarkers in Cancer Patients Receiving Immune Checkpoint Inhibitors

<b>Background:</b> Immune checkpoint inhibitors have significantly improved outcomes in select cancers; however, not all patients respond to these therapies, and the duration of the response varies among responders. Markers predictive of the response to immunotherapy, such as PD-L1 expression determined by immunohistochemical staining of tumor sections and microsatellite status, have been identified. Some of these are used in companion diagnostics approved for clinical practice. Additional easy-to-use biomarkers may help clinicians to predict the efficacy of these drugs in individual patients. <b>Materials and Methods:</b> A retrospective review of the medical records of patients with metastatic cancer treated with immune checkpoint inhibitors in our cancer center was performed to identify the clinical and hematologic parameters associated with survival outcomes. <b>Results:</b> Among the 163 patients included in the study, most had lung cancer, followed by kidney cancer, melanoma, and bladder cancer. Most patients (61.3%) were male and had good performance status. Nivolumab and pembrolizumab were immune checkpoint inhibitors utilized in 85.9% of cases. Age, sex, and primary cancer type were not associated with survival outcomes. Among the peripheral blood parameters evaluated, lymphocytopenia was the strongest predictor of adverse survival outcomes in univariate analysis and the only clinical or hematologic biomarker that retained significance for overall survival (OS) prediction in multivariate analysis. <b>Conclusion:</b> Among the clinical and hematologic parameters routinely used in the clinic, a lymphocyte count below 1 x 10⁹/ L was predictive of adverse OS in patients with metastatic cancers receiving immune checkpoint inhibitors.