Evaluation of MMR Status and PD-L1 Expression Using Specimens Obtained by EUS-FNB in Patients With Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) has a suboptimal response to standard therapies that modestly impact survival due to its ability to evade host immune surveillance. Emerging evidence has shown that the co-inhibitory receptors, such as programmed death 1 (PD-1), play a critical role in cancer immune-editing. Programmed death-ligand 1 (PD-L1) is an immune checkpoint that is often activated in cancer and plays a pivotal role in the initiation and progression of cancer. The advent of immunotherapy, with checkpoint inhibitors, which block PD-L1 interaction between tumor cells and activated T cells, has significantly altered the treatment algorithm for several solid tumors. However, the clinicopathologic significance and prognostic value of PD-L1 in PDAC remains controversial. The main technical ground may be that PDAC PD-L1 expression quantification is limited to surgical resection specimens and dependent on specific immunohistochemistry (IHC) tests. In addition, PD-L1 expression has not been extensively assessed before surgery in treatment-naive PDAC patients, due to the current IHC test requirement for a histologic rather than a cytologic evaluation. However, a recent study showed that EUS-fine needle biopsy (FNB) can successfully determine primary pancreas malignancy PD-L1 status. One recently identified subtype within the genomic landscape of PDAC is the mismatch repair-deficient (dMMR) tumor. Evaluation of dMMR status is particularly important following the FDA approval of the PD-1 inhibitor, pembrolizumab, for the treatment of unresectable or metastatic, microsatellite instability-high (MSI-H) or dMMR PDAC that have progressed following prior treatment, and have no satisfactory alternative treatment options. The objectives of the project will include the assessment of tumor PD-L1/dMMR expression in patients with PDAC using EUS-FNB samples and the prospective correlation of MMR status and PD-L1 expression with overall survival and progression-free survival