Retrospective analysis of Claudin18.2 expression in ethnically diverse patients with gastroesophageal adenocarcinoma.

Background: Claudin18.2 (CLDN18.2), a tight junction molecule, is a novel therapeutic target for patients with advanced gastroesophageal adenocarcinoma. Recent phase III trials demonstrated improved survival with the addition of an anti-CLDN18.2 antibody (zolbetuximab) to first-line chemotherapy. However, expression of CLDN18.2 and its association with other biomarkers, especially in racial and ethnic minorities, remains poorly defined. We evaluated CLDN18.2 expression, its association with demographic and clinicopathologic characteristics, and its prognostic potential in a cohort of ethnically diverse patients. Methods: We conducted a single-center retrospective cohort study among patients with gastric, gastroesophageal, and esophageal adenocarcinoma in whom CLDN18.2 immunohistochemistry had been performed. Positivity was defined as moderate-to-strong expression in ≥75% of tumor cells. We extracted demographic and clinicopathologic data from the electronic medical record. Associations with CLDN18.2 were investigated using the Results: Among 75 evaluable patients, 32 (42.7%) were CLDN18.2 positive. Mean age was 66.2 years [standard deviation (SD), 13.2 years], 34.7% were female, and 62.7%, 18.7%, and 18.7%, had primary gastric, gastroesophageal junction, and esophageal tumors, respectively. At diagnosis, 32% were metastatic. The cohort was 49.3% White, 12% Black, 8% Asian, 21.3% other, and 9.3% unknown, and 20% identified as Hispanic. By ethnicity, 53.3% of Hispanic patients were CLDN18.2 positive compared to 38.2% of non-Hispanic patients. By race, 37.8% of White, 44.4% of Black, and 50% of Asian patients were CLDN18.2 positive. In univariate analyses, CLDN18.2 positivity was significantly associated with female sex (P=0.002) and human epidermal growth factor receptor 2 (HER2) negativity (P=0.03). Conclusions: This study provides new information on CLDN18.2 expression in an ethnically diverse population and suggests that Hispanic patients may have higher rates of CLDN18.2 positivity than non-Hispanic patients. We also demonstrate the association between CLDN18.2 and female sex and HER2 negativity and lack of association with survival, consistent with published data. Future research should further investigate differences in CLDN18.2 expression and identify subpopulations of patients who may benefit from CLDN18.2-targeted therapies.