Biomarker landscape and survival outcomes in gastric adenocarcinoma: A Hispanic/Latino cohort from Colombia (2010–2024).

Abstract

e16088 Background: Hispanic patients with gastric adenocarcinoma show distinct clinical patterns, including earlier onset, increased mortality, and a distinct molecular profile. Despite recognition that ethnicity shapes tumor biology and precision oncology access, Latin American real-world data on this disease remain scarce. Methods: We conducted a retrospective observational cohort study of adults diagnosed with gastric adenocarcinoma treated at Fundación Santa Fe de Bogotá between 2010 and 2024. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan–Meier (KM) method. Survival curves were compared using the log-rank test, and Cox proportional hazards regression models were performed to identify factors associated with OS and PFS. Results: A total of 166 patients were included; 51.8% were female, with a median age of 66 years (IQR 25). Stage IV disease was frequent (37.6%), predominantly involving the peritoneum (70.4%). Notably, 18.1% of patients were asymptomatic at diagnosis. Diffuse-type histology was most common (47.6%), and 60.6% of tumors were grade III. HER2 overexpression (IHC 3+) and MSI-high status were observed in 6.1% and 6.8%, respectively. Biomarker testing was available in a subset of patients: MSI status was assessed in 79 patients, with 13.9% classified as MSI-high, and HER2 status was evaluated in 106 patients, of whom 13.2% were HER2-positive. Systemic therapy was administered to 82.9% of patients, with chemotherapy as the backbone of treatment (97.0%), the most commonly used regimens were FOLFOX (25.9%) and FLOT (22.3%), followed by CAPEOX (6.0%) and DCF (3.6%). After a median follow-up of 41.0 months using the reverse KM method, median OS and PFS were not reached. Twelve- and 24-month OS rates were 77.6% (95% CI, 70.0–83.6) and 62.9% (95% CI, 54.2–70.4), respectively, while corresponding PFS rates were 58.4% and 41.0%. Disease stage was a strong predictor of both OS and PFS (p < 0.001 for both). OS differed according to MSI status, with MSI-high tumors associated with significantly improved survival (HR 0.13, 95% CI 0.02–0.90; p = 0.048). In contrast, HER2-positive status was not associated with OS (adjusted HR 0.71, 95% CI 0.25–2.00; p = 0.52). Conclusions: Diffuse histology and peritoneal metastasis were frequent in this Hispanic cohort, while HER2 overexpression and MSI-high status were uncommon, limiting targeted and immunotherapy-based approaches. Notably, MSI-high status was associated with significantly improved OS, indicating that the low prevalence of this subtype in our population may contribute to the overall poorer prognostic profile. Despite advanced-stage presentation, survival outcomes were comparable to international real-world series, highlighting the distinct biologic profile of gastric cancer in Hispanic populations and the need for greater representation in clinical research.