Association of programmed death ligand 1 expression with prognosis among patients with ten uncommon advanced cancers

Aim: PD-L1 expression and high levels of microsatellite instability (MSI-H) may predict response to checkpoint inhibitors, but their prevalence and prognostic value are unknown in many cancers. Methods: We retrospectively evaluated PD-L1 combined positive score (CPS) and MSI-H and their association with clinical outcomes among patients with ten advanced uncommon cancers. Results: 398 of 426 patients (93%) had a valid PD-L1 result; most (242; 61%) had CPS ≥1. Prevalence of MSI-H tumors was 8/360. Median overall survival was shorter among patients with PD-L1 CPS ≥1 tumors after first-line treatment (23.0 vs 39.7 months, p = 0.014). Conclusion: PD-L1 was commonly expressed in solid tumors, and CPS ≥1 was associated with shorter overall survival. Prevalence of MSI-H was low. Lay abstract Certain biologic characteristics of tumors (or biomarkers) may be used to assess the likely course of a patient's disease (i.e., their prognosis) and/or how they may respond to treatment. We evaluated whether the presence of the protein PD-L1 and high levels of microsatellite instability were associated with overall survival among patients with ten uncommon advanced cancers. PD-L1 was commonly expressed in solid tumors and its presence may be associated with shorter overall survival. Prevalence of high microsatellite instability was low.