Prevalence of claudin 18.2 (CLD18.2) in gastric cancers and clinical correlation.

e16025 Background: There is no data from India about the prevalence of CLD18.2 in patients with gastric adenocarcinomas (GC). Methods: Records of treatment-naive histologically confirmed GC diagnosed between January 2018 and October 2023 were retrieved from a prospectively maintained GC database at Tata Memorial Hospital in Mumbai. CLD 18.2 estimation was conducted by the Ventana CLDN18 (43-14A) RxDx Assay (Ventana Medical Systems, Inc./Roche Diagnostics) on the archival paraffin blocks. CLD 18.2 expression was considered positive if moderate to strong expression was seen in at least 75% of the tumor cells. The study's primary endpoint was to determine the prevalence of CLD18.2 positivity in GC, while secondary endpoints aimed at correlating clinicopathological variables and overall survival (OS) with CLD18.2 expression. Results: Six hundred specimens were screened, with adequate blocks and treatment details available to 300 patients. The median age of patients was 51 years (range 23-83 years). Most patients were males (67%), and had poorly differentiated histology (64%). Curative resection was performed in 38 % of patients. CLD18.2 positivity was seen in 95 cases (31.7%). CLD18.2 positivity was significantly correlated with signet ring histology (62% vs. 39 %; p = < 0.001), combined proportionate score (CPS) < / = 5 (37 % vs 17 %, p = 0.013), and female gender (42% vs 29 %; p = 0.025). Median overall survival in the CLD18.2 positive population was 14.1 months (95%CI 8.9-19.3), as compared to 19.5 months (95%CI 14.4-24.6) in those who tested negative, though the difference did not reach statistical significance (p = 0.361). Conclusions: Claudin 18.2 positivity is seen in approximately 32% of Indian patients with gastric cancers and shows a greater correlation with signet ring histology, female gender, and lower CPS in these patients. Claudin 18.2 positive patients tended to have inferior survivals compared to Claudin 18.2 negative patients, though this needs further evaluation.