S3110 Proportions and Outcomes of Post-Endoscopy Gastric Cancer in a U.S. Real-World Cohort

Introduction: “Post-endoscopy” gastric cancer (PEGC) describes malignancy detected 6-36 months after a prior esophagogastroduodenoscopy (EGD) in which no gastric cancer was detected. While interval esophageal cancer has received well described, contemporary U.S. data on PEGC are scarce. We aimed to assess burden and 3-year clinical outcomes of PEGC compared to gastric cancers diagnosed ≤6 months after EGD (“prevalent” GC). Methods: Using the TriNetX U.S. Collaborative Network, we identified adults (18-90 years old) carrying the ICD code for GC between 2005 and 2022. A diagnosis of PEGC required a documented EGD 6-36 months before the index cancer; while a diagnosis of prevalent GC required an EGD within the preceding 6 months. Patients with prior malignancies were excluded. Propensity scores built from age, sex, race/ethnicity, cardiovascular-metabolic disease, smoking, alcohol and BMI generated a 1:1 matched cohort (n = 353). Outcomes (gastrectomy, chemotherapy, inpatient hospitalization, radiation therapy, and all-cause mortality) were calculated over 3 years. Cox models yielded hazard ratios (HRs) with 95% confidence intervals (CIs). Results: Among 7,629 GC over 3 years, 376 fulfilled PEGC criteria, constituting 4.9% of all diagnosed GC. Proportions of PEGC within the GC cohort stratified by sex: 4.0% in men (191/4,760); 6.6% in women (188/2,844). By race, Whites showed a PEGC proportion of 4.6% (212/4,594), whereas the aggregated “other-race” group (Black, Asian, American Indian/Alaska Native, Native Hawaiian/Pacific Islander, and Other) had a higher proportion at 7.2% (145/2,004). Proportions of PEGC within the GC cohort stratified by ethnicity: 4.2% in Hispanics (36/855); 5.7% in non-Hispanics (268/4,695). After matching, PEGC showed significantly lower chance of receiving chemotherapy (HR 0.46; CI 0.34-0.61), hospitalization (HR 0.61; CI 0.45-0.84), radiation (HR 0.36; CI 0.22-0.59) and mortality (HR 0.62; CI 0.47-0.82). Resection rates were numerically lower but not significant (HR 0.56; CI 0.27-1.17) in PEGC cohort. Absolute 3-year mortality was 24% in PEGC compared to 35% in prevalent GC (risk difference -10.8%; P = 0.002). Conclusion: Our large database study suggests that 5% of all GC are PEGC, disproportionately affecting women and racial minorities. PEGC has markedly better mortality outcome and treatment profile than prevalent GC, suggesting tumor detection at earlier stage with favorable tumor biology.