P1.09-22 Programmed Death Ligand-1 Expression in Non-Small Cell Lung Cancer in Mexican Population and Correlation with Clinicopathologic Features

Abstract

Immune checkpoint inhibition is an important therapeutic option in patients with non-small cell lung cancer. Programmed cell death ligand-1 (PD-L1) expression may serve as a predictive and prognostic factor for anti-PD-1/PD-L1 therapies. We conducted a national, retrospective, observational study to determine PDL1 prevalence and correlation with clinicopathologic features. Patients with histologic confirmed stage III/IV NSCLC and available tissue block were included. PDL1 tumor expression was performed with PDL1 IHC (SP263) assay on a Ventana Benchmark XT platform. Tumor cell PD-L1 expression was scored as Tumor Proportion Score (TPS) and classified as negative (<1%), 1-49% and ≥ 50% for correlation with clinicopathologic features. Of a total of 948 patients included in the study, 170 (18%) were TPS >50%, 333 (35%) and 445 (47%) were TPS 1-49% and negative (<1%) respectively. The TPS was higher in squamous cell carcinomas (p=0.001) due to increased proportion of strong expression (>50%). Among the 778 non-squamous carcinomas, 187 (24%) had EGFR mutations and 31 (4%) showed ALK translocations. A TPS >50% was seen in 25% (47/187) and 21% (6/31) EGFR mutant and ALK translocated tumors, respectively. The overall prevalence of TPS ≥50% is slightly lower than previously reported. TPS was significantly higher in squamous cell carcinomas and there was no correlation between PD-L1 expression and molecular abnormalities, or age, gender and smoking status.