Relationship between PD-L1 expression and survival in head and neck squamous cell carcinoma (HNSCC) patients (pts)

Abstract

Background: Programmed cell death 1 (PD-1) and its ligand 1 (PD-L1) are upregulated in many cancers. The purpose of this study was to explore the relationship between PD-L1 expression and overall survival (OS) in HNSCC. Methods: A retrospective study was conducted using data from pt medical records and analysis of archival tumor samples. Sample ages ranged from 8.2 to 227.5 months. Pts ≥18 years old diagnosed with HNSCC between 1989 and 2015 were selected. Demographic and tumor characteristics were compared by PD-L1 expression status. PD-L1 testing was performed using the Ventana PD-L1 SP263 assay. PD-L1 expression was scored separately using tumor cell (TC) and immune cell (IC) membrane staining and exploratory cut-offs of 1%, 5%, 10%, 25% and 50%. OS was calculated as the number of months from initial HNSCC diagnosis until death and estimated using the Kaplan-Meier method. The log-rank test was used to compare survival curves by PD-L1 status. PD-L1 status as a prognostic indicator of OS was further examined in Cox proportional hazards (PH) models. Results: We identified 214HNSCC pts with data available for date of death/last follow-up and PD-L1 status. Mean (SD) tumor sample age was 93.3 (40.5) months. Mean (SD) pt age was 62.3 (13.4) years and 70%weremale. The Table presents baseline characteristics by PD-L1 subgroup. Median OS was similar between PD-L1 high and low/negative pts classified using the TC ≥25%, IC ≥1%, and IC ≥25%cut-offs. However, median OS was 21.2months longer in PD-L1 high versus low/negative pts (68.9 vs. 47.7months, respectively; P=0.03) in analyses using the TC ≥1%cut-off. This latter relationship remained after adjusting for baseline covariates using Cox PHmodels. Conclusions: PD-L1 high expression based on a TC ≥1% cut-off appears to be associated with improved OS in this sample of pts withHNSCC. A small number of samples and resulting low statistical power limited our ability to assess prognosis for TC ≥25%and IC ≥25%, yetOS was numerically higher among PD-L1 high pts in these subgroups. (Table Presented).