1049PD - 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 up-regulated 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 214 HNSCC 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% were male. 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 21.2 months longer in PD-L1 high versus low/negative pts (68.9 vs. 47.7 months, respectively; P=0.03) in analyses using the TC ≥ 1% cut-off. This latter relationship remained after adjusting for baseline covariates using Cox PH models.Table1049PD Baseline characteristicsCharacteristicTC PD-L1 expressionHigh (≥25%)Low/negative (<25%)High (≥1%)Low/negative (<1%)No. of pts (%)33 (15.4)181 (84.6)118 (55.1)96 (44.9)Mean (SD) age, years57.3 (12.3)63.2 (13.4)61.1 (12.9)63.8 (13.8)HPV positive, %42.445.345.843.8Present smoker, %24.236.531.438.5Stage IV, %33.351.448.349.0African American, %27.316.622.912.5Median OS, monthsNot reached62.968.947.7p-value*log-rank p-value comparing high vs. low/negative groups0.270.03IC PD-L1 expressionHigh (≥25%)Low/negative (<25%)High (≥1%)Low/negative (<1%)No. of pts (%)11 (5.1)203 (94.9)150 (70.0)64 (30.0)Mean (SD) age, years63.8 (10.1)62.2 (13.6)61.3 (13.4)64.6 (13.2)HPV positive, %8 (72.7)88 (43.4)75 (50.0)21 (32.8)Present smoker, %3 (27.3)71 (35.0)53 (35.3)21 (32.8)Stage IV, %6 (54.5)98 (48.3)68 (45.3)36 (56.3)African American, %4 (36.4)35 (17.2)31 (20.7)8 (12.5)Median OS, months157.168.979.052.5p-value*log-rank p-value comparing high vs. low/negative groups0.310.07* log-rank p-value comparing high vs. low/negative groups Open table in a new tab Conclusions: PD-L1 high expression based on a TC ≥ 1% cut-off appears to be associated with improved OS in this sample of pts with HNSCC. A small number of samples and resulting low statistical power limited our ability to assess prognosis for TC ≥ 25% and IC ≥ 25%, yet OS was numerically higher among PD-L1 high pts in these subgroups. Legal entity responsible for the study: AstraZeneca Funding: AstraZeneca Disclosure: M. Stokes: Employment (Evidera) and research funding (Evidera). R. Wang: Employment (Evidera) and Stock ownership (Evidera). S. Wildsmith, H.K. Angell, C. Barker, J. Walker, P. Scorer, N. Shire: Employment (AstraZeneca) and Shareholder (AstraZeneca). M. Secrier: Employment (AstraZeneca) Corporate sponsored research (AstraZeneca) and Shareholder (AstraZeneca). M.C. Rebelatto: Employment (AstraZeneca/MedImmune) and Shareholder (AstraZeneca/MedImmune).