The circulating PD-L1: An emerging predictive biomarker for immune checkpoint inhibitors response

Immune checkpoint inhibitors (ICI) have recently become the standard of care for many metastatic solid tumors, with considerable improvements in patient prognosis. However, a nonnegligible proportion of patients does not respond to this type of treatment, making it essential to identify predictive factors of this response in order to better adapt the therapy. Among the biomarkers that have been most extensively studied in recent years, tumor PD -L1 levels come out on top, with controversial results for predicting response to ICI. The determination of circulating PD -L1 (or soluble PD -L1) in peripheral blood seems to be an interesting emerging biomarker. Indeed, several studies have investigated its prognostic value, and/or its potential predictive value of response to immunotherapy, and it would appear that there is a correlation between the level of soluble PD -L1 and the level of tumor aggressiveness and therefore prognosis. Furthermore, the results suggest that higher PD -L1 levels are associated with a poorer response to immunotherapy, although this remains to be con fi rmed in large-scale studies.