Real-world characterization of PD-L1 expression in patients with advanced esophagogastric adenocarcinoma in Spain

PURPOSE: Epidemiological data from Sapin are lacking, especially in a publication relating Spanish data and prevalence of programmed cell death ligand-1 (PD-L1) expression. This study aimed to evaluate the prevalence of PD-L1 expression by Combined Positive Score (CPS) ≥ 5 in patients with advanced esophagogastric adenocarcinoma (aEGAC) in Spain. METHODS: This observational, retrospective, and multicenter study collected sociodemographic and clinical data from adult patients with locally advanced unresectable, recurrent, or metastatic EGAC across 21 centers in the AGAMENON-SEOM registry. CPS PD-L1 expression was centrally analyzed using the IHC 28-8 pharmDx. RESULTS: A total of 166 patients were included, with 144 valid and evaluable samples. The primary tumor locations were stomach (70.1%), gastroesophageal junction (19.4%), and esophagus (10.4%). At diagnosis, 84.0% had synchronous metastatic disease, 4.9% had unresectable locally advanced disease, and 11.1% had recurrent disease. PD-L1 CPS ≥ 5 was observed in 41.7% of the patients (95%CI, 34.3-50.4%). Prevalence by tumor type was 41.6% (95% CI, 32.0-51.2%) in gastric adenocarcinoma, 35.7% (95% CI, 18.0-53.5%) in gastroesophageal junction adenocarcinomas, and 60.0% (95% CI, 35.2-84.8%) in esophageal adenocarcinoma. PD-L1 CPS ≥ 5 was found in 42.9% (95% CI, 6.2-79.5%) of patients with unresectable locally advanced disease, 43.0% (95% CI, 34.2-51.8%) of those with metastatic disease, and 37.5% (95% CI, 13.8-61.2%) of those with recurrent disease. CONCLUSION: This is the first study to report the real-world prevalence of PD-L1 expression in patients with aEGAC in clinical practice in Spain. These findings underscore the importance of understanding PD-L1 prevalence in the Spanish population and investigating discrepancies with previous studies.