Quantification of PD-L1 expression and tumor mutational burden in biologically distinct advanced pancreatic cancers responding to pembrolizumab: case reports

Abstract

Background: The advent of checkpoint therapy is one of the most important recent advancements in cancer therapy. Though checkpoint therapy is a mainstay in some cancers, it has been largely ineffective in treating cancers of the pancreas. Pancreatic ductal adenocarcinoma and pancreatic neuroendocrine tumors are seldom responsive to checkpoint inhibition.

Case presentations: Here we present two cases of advanced pancreatic cancers that either failed to respond or recurred following conventional treatments. Tissue from each tumor was sequenced and analyzed for PD-L1 expression. Each patient was started on checkpoint blockade after assessing for a predictive biomarker, either the combined positive score or the tumor mutational burden. In each case, checkpoint blockade led to durable radiographic responses.

Conclusions: We therefore propose that it is reasonable to assess combined positive score and tumor mutational burden in refractory or recurrent pancreatic cancers when initiation of ICB is being considered.

Keywords: CPS; TMB; immunotherapy; pancreatic adenocarcinoma; pancreatic neuroendocrine tumor.