PD-1/PD-L1 expression and regorafenib clinical efficacy on refractory pancreatic cancer patient.

e15684Background: Regorafenib, a potent multikinase inhibitor, targets a broad range of receptor tyrosine kinases (RTKs), including but not limited to VEGFR, PDGFR, and FGFR, which play an integral role in angiogenesis and in making a immunosuppressive tumor microenvironment. The results of the correlation between PD-1/PD-L1 expression and RTKs inhibition remains controversial in lung cancer and limited data exist in pancreatic cancer. Methods: We analysed a cohort of 69 chemorefractory metastatic pancreatic cancer patients, including 56 KRAS mutated, treated with Regorafenib as third line of treatment. PD-L1 (MRQ-22 antibody) and PD-1 (SP142 antibody) expression were assessed by immunohistochemistry. All cases with moderate or strong staining (2+/3+) in > 5% of tumour cells and tumor infiltrating lymphocytes (TILs) were considered as positive. Results: Pancreatic tumors expressed PD-L1 at a frequency of 20% (14/69), and PD-1 at a frequency of 46% (32/69). PD-1 positive (+) was significantly associated wi...