EUS fine-needle pancreatic core biopsy can determine eligibility for tumor-agnostic immunotherapy

Background and study aims  The US FDA recently approved a cancer treatment with pembrolizumab based upon the tumor biomarker status of deficient mismatch repair (dMMR) rather than a specific disease-based approach. We sought to determine if endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) could determine dMMR and quantification of PD-L1 expression to potentially guide the delivery of tumor agnostic immunotherapy. Patients and methods  Immunohistochemistry was performed on archived pancreas core biopsy specimens. Tumors with absent nuclear staining of DNA mismatch repair proteins represented dMMR. Tumors were considered to have any or high PD-L1 expression, if expressed in ≥ 1 % or ≥ 50 % of tumor cells. Results  Histologic specimen adequacy for MMR status assessment was satisfactory in 97.2 % of tumors. dMMR and high PD-L1 expression was identified in 3 % and 8.1 % of the cohort. Conclusion  In the setting of tumor type agnostic immunotherapy, it is projected that at least 3 % of malignant pancreas lesions will be sensitive to pembrolizumab and up to 8 % sensitive to the family of immune checkpoint inhibitors. This highlights the expanding role of EUS-FNB in the field of precision immuno-oncology.