Inpatient burden and outcomes across gastrointestinal cancer subtypes among younger adults in the United States, 2018–2022.

11077 Background: Early-onset gastrointestinal (GI) cancers are increasingly recognized, yet national data describing inpatient burden and outcomes across GI cancer subtypes in younger adults remain limited. Methods: A serial cross-sectional analysis was performed using the 2018–2022 Healthcare Cost and Utilization Project National Inpatient Sample. Adult hospitalizations among younger adults (age 18–49 years) with a principal diagnosis of GI malignancy were identified and categorized by cancer subtype. Outcomes included in-hospital mortality (primary), length of stay (LOS), and hospitalization cost estimated using cost-to-charge ratios. National estimates accounted for survey weighting, clustering, and stratification. Survey-weighted multivariable logistic regression evaluated associations between cancer subtype and in-hospital mortality, adjusting for age, sex, race/ethnicity, payer, neighborhood income quartile, elective admission, APR-DRG severity, hospital teaching status, geographic region, and calendar year. Sensitivity analyses were performed restricting the cohort to age < 45 years. Results: Across 2018–2022, principal GI cancer hospitalizations among younger adults were dominated by colorectal cancer, followed by stomach, pancreatic, liver or intrahepatic biliary, and esophageal cancers. In-hospital mortality varied by cancer subtype and year, with higher crude mortality observed for pancreatic, stomach, esophageal, and liver or intrahepatic biliary cancers compared with colorectal cancer. Resource utilization increased markedly during 2020 across subtypes, with corresponding increases in LOS and hospitalization costs. In adjusted analyses using colorectal cancer as the reference, odds of in-hospital mortality were higher for stomach (adjusted odds ratio aOR 3.01, 95% CI 1.78–5.10), esophageal (aOR 2.12, 95% CI 1.03–4.37), and liver or intrahepatic biliary cancers (aOR 2.56, 95% CI 1.36–4.79). Pancreatic cancer demonstrated a borderline increase in mortality (aOR 1.79, 95% CI 0.96–3.36). Higher APR-DRG severity was strongly associated with mortality (aOR 5.20, 95% CI 3.50–7.72). Sensitivity analyses demonstrated similar subtype ordering and mortality patterns. Conclusions: Among younger adults hospitalized with GI malignancies, inpatient mortality and resource utilization varied substantially by cancer subtype. Colorectal cancer accounted for the largest share of hospitalizations, while stomach, esophageal, and liver or intrahepatic biliary cancers were associated with higher adjusted inpatient mortality. These nationally representative findings provide benchmarking data on inpatient outcomes across early-onset GI cancer subtypes.