Detection of PD-L1 on blood circulating tumor cells

What is it about?

In 2015, PD-L1 expression on tumor biopsy became the first companion diagnostic in immunotherapy. Cancer patients whose tumor cells express the PD-L1 protein are more likely to gain benefit from Anti-PD-1 cancer immunotherapy. Since then exploratory efforts have focused on the measurement of PD-L1 on tumor cells circulating in blood. This is the first review of the progress made and challenges facing this emerging field.

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Why is it important?

It is easier to obtain blood samples as opposed to tumor biopsy for the measurement of this biomarker. This would facilitate measuring this biomarker more frequently during treatment. It could also given a better picture of this biomarker than a single biopsy sample from what could be a very heterogeneous tumor.