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

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.