PD-1 and PD-L1 Expression in Endometrial Cancer: A Systematic Review of the Literature
Orazio De Tommasi, Matteo Marchetti, Marta Tripepi, Sofia Bigardi, Giosuè Giordano Incognito, Valentina Tuninetti, Emma Facchetti, Giulia Tasca, Marco Noventa, Carlo Saccardi, Roberto Tozzi, Giulia Spagnol
Abstract
Background/Objectives: Cancer immunotherapy through the use of PD-1/PD-L1 inhibitors have shown significant promise in endometrial carcinoma (EC), particularly in tumors with microsatellite instability (MSI) or mismatch repair deficiency (dMMR), present in approximately 30% of cases. This review evaluated PD-L1 and PD-1 expression as potential biomarkers for immunotherapy response in EC, focusing on their relationship with MSI status. Methods: A systematic review, adhering to PRISMA guidelines, analyzed studies from MEDLINE and Embase until February 2023 on PD-1/PD-L1 expression in EC stratified by MSI status, including diverse study designs but excluding conference abstracts, with independent screening, data extraction, and additional reference checks to ensure comprehensive coverage. Results: A systematic analysis of 10 studies found that PD-L1 expression was more frequently expressed in MSI tumors (49%) compared to microsatellite-stable tumors (MSS) (33.5%), while PD-1 was expressed in 58% of MSI cases and 48% of MSS cases. Despite these findings, the prognostic value of PD-L1/PD-1 remains uncertain, with conflicting results regarding their association with survival outcomes. PD-L1 expression varied across molecular subtypes, being highest in POLE-mutated tumors (76.56%) and serous carcinomas (73%). Differences in PD-L1 expression between primary and metastatic sites were also noted, complicating its use as a biomarker. Conclusions: The assessment of PD-L1 expression in EC could represent a valuable option for selecting patients who may benefit from immune checkpoint inhibitors (ICI), including those in the MSS cohort, thereby ensuring a more tailored and personalized treatment strategy.