PD-L1 Expression in Ampullary Adenocarcinoma.

Introduction: Ampullary adenocarcinoma is a rare neoplasm often treated by the complex Whipple's procedure. Several histological factors predict poor prognosis including pancreatobiliary morphology, presence of lymphovascular, perineural invasion and local or distant metastasis. Systemic therapy with gemcitabine, 5-fluorouracil regimens are given with variable benefits. Immunotherapy checkpoint inhibitors have shown beneficial anti-tumor effects in several carcinomas, the most remarkable being in non-small cell lung cancer. Administration of these novel drugs is based on immunohistochemical expression (which may or may not be indicative of response to therapy) along with meticulous decision making by the multidisciplinary team. Immunohistochemistry (IHC) is an effective means of immune marker demonstration and has been used in various tumor types for predictive and prognostic purposes.

Methods: PD-L1 IHC (clone E1L3N) was applied in 101 cases of ampullary adenocarcinoma. Tumor infiltrating lymphocytes were also evaluated. The immunoreactivity was assessed and categorized into following staining thresholds: <1%, <5%, <10% and ≥10% for tumor cells (membranous and/or cytoplasmic staining pattern), and 5% and 10% cut-offs for immune cells.

Results: We found that at a 10% cut-off, 73.3% (74/101) patients were men (  =  .006) older than 50 years of age ( < .001) presenting with a tumor measuring <3 cm (  =  .001). It was significantly associated with intestinal differentiation (  =  .004) and grade 1 tumors (  =  .001). Twelve patients presented with recurrence as well (  =  .03).

Conclusion: In the context of ampullary adenocarcinoma, this study highlights the positivity observed with the PD-L1 IHC clone E1L3N at different thresholds, with the particularly stronger associations being evident at a 10% cut-off.