Prognostic and Clinical Heterogeneity of PD1 and PD-L1- Immunohistochemical Scores in Endometrial Cancers

PD1/PD-L1 inhibition (ICi) has recently become a new standard of care for patients with advanced MMR-deficient (MMRd) endometrial cancers. Nevertheless, response to immunotherapy is more complex than the presence of a single biomarker and therefore it remains challenging to predict patients response to ICi beyond MMRd tumors. Elevated PD-L1 expression (CPS ≥ 1) is often used as a prognostic marker as well as a predictive biomarker of response to ICi in different tumor types. In a retrospective, patient derived study, we analyzed PD1- and PD-L1 staining and correlated the results of different scores to clinical data to evaluate the prognostic impact of these scores. Immunohistochemical analysis of the receptor PD1 and the receptor ligand PD-L1 were performed on TMAs of primary paraffin‑embedded tumor samples. All patients were treated for primary endometrial cancer in the Department of Gynecology and Obstetrics, University Medical Center Schleswig–Holstein, Campus-Lübeck, Germany between the years 2006–2018. The evaluation and determination of the tumor proportion scoring (TPS), the combined positive score (CPS) and the immune cell scoring (IC) was automatically assessed semi-quantitatively, and results were correlated with clinicopathological characteristics and survival. 130 samples were evaluable and 64