Abstract

ABSTRACT Background There has been a paradoxical rise in young‐onset gastric cancer (YOGC), defined as gastric cancer (GC) diagnosed before age 50. Precursor lesions may contribute to pathogenesis, though their role in progression to different histologic subtypes is unclear. The impact of self‐reported race is also poorly characterized and may be unreliable as a proxy for genetic differences. We aimed to compare differences in histology and genetic ancestry between YOGC and average‐onset gastric cancer (AOGC). Methods This retrospective cohort included all patients with GC at Memorial Sloan Kettering (MSK) from January 2013 to March 2021. Data on demographics, tumor characteristics, and precursor lesions were collected. Genetic ancestry was inferred from MSK‐Integrated Mutation Profiling of Actionable Cancer Targets panel. Results Of 1685 individuals with GC, 290 had YOGC. Compared to AOGC, individuals with YOGC tended to be female, Hispanic, foreign‐born, and feature diffuse‐type histology. YOGC was less likely to have precursor lesions, including intestinal metaplasia (20% vs. 37%, p < 0.01) and dysplasia (4% vs. 14%, p < 0.01). Of 560 patients with ancestry data, 127 had YOGC. Admixed, East Asian, and South Asian ancestries were more likely to present with YOGC while Europeans presented with AOGC. Intestinal metaplasia was enriched among East Asians, maintained when stratifying by histology and GC onset. Conclusions We observed YOGC was more common in East and South Asians, and while YOGC may be less likely to develop in the setting of precursor lesions these high‐risk states may also be enriched in East Asians. Future research is needed to understand drivers behind such differences and outcome disparities given these individuals may be less amenable to endoscopic interventions.