Correlation of clinical outcomes with programmed death ligand-1 expression on liquid biopsy.

Abstract

e21050 Background: Programmed death ligand-1 (PD-L1) expression is predictive of immunotherapy benefit. However, tissue PD-L1 protein immunohistochemical testing can be fraught with tissue acquisition and heterogeneity limitations. PD-L1 expression by RNA sequencing can be performed by both tissue and plasma with tissue PD-L1 protein correlations. What has not been well characterized is the correlation of plasma cell free circulating tumor RNA (cfRNA) PD-L1 and clinical outcomes with immunotherapy. Plasma cfRNA PD-L1 expression was evaluated and correlated with immunotherapy benefit in advanced non-small cell lung cancers (NSCLC). Methods: Patients with advanced NSCLC undergoing plasma next-generation sequencing including plasma cfRNA.PD-L1 testing in a Clinical Laboratory Improvement Amendments (CLIA) and College of American pathologists (CAP) accredited laboratory were retrospectively identified and evaluated at a single institution. Plasma PD-L1 positive patients underwent a de-identified chart abstraction to identify those patients with advanced NSCLC treated with front line immunotherapy regimens and those who received cytotoxic chemotherapy alone. Results: Sixteen patients with plasma PD-L1 expression treated with front-line immunotherapy regimens including single-agent immune checkpoint inhibitors, and combinatorial chemo-immune or chemo-immune-bevacizumab regimens were assessed for overall survival (OS). Eleven patients with plasma PD-L1 expression who received chemotherapy were used as a non-immunotherapy OS comparison. Median OS for the immunotherapy treated patients was thirteen months with a thirty percent three year landmark OS versus four months median OS and a ten percent three-year landmark OS for those treated with chemotherapy alone. Comparative log-rank test p-value 0.0091 and a hazard ratio of 0.36 (95%-CI 0.13-0.99). Conclusions: Plasma cfRNA PD-L1 expression is predictive of a statistically significant survival benefit from immunotherapy treatment compared to chemotherapy in the first line treatment of advanced NSCLC. The three year landmark OS of thirty percent parallels tissue PD-L1 directed immunotherapy-based treatment outcomes. The clinical utility of plasma cfRNA PD-L1 to overcome tissue acquisition and PD-L1 protein heterogeneity limitations and to study the dynamic nature of PD-L1 expression with non-immune cancer treatments and potential immunotherapy response monitoring are undergoing ongoing research.