National trends, disparities, and inpatient outcomes in appendiceal adenocarcinoma: A U.S. nationwide analysis, 2016–2021.

e23356 Background: Appendiceal adenocarcinoma is a rare gastrointestinal malignancy with heterogeneous inpatient management ranging from limited resection to cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS/HIPEC). Large, contemporary population-level data examining inpatient management patterns and disparities are lacking. We evaluated national trends, treatment utilization, and demographic disparities among adults hospitalized with appendiceal adenocarcinoma in the United States. Methods: We analyzed the Nationwide Inpatient Sample (2016–2021) to identify adult hospitalizations with a principal diagnosis of malignant neoplasm of the appendix, applying survey weights for national estimates. Management strategies were classified as appendectomy, right hemicolectomy, CRS/HIPEC, or no surgery. CRS/HIPEC was identified using procedural codes, acknowledging potential under-capture in administrative data. The primary outcome was in-hospital mortality. Secondary outcomes included length of stay (LOS), prolonged hospitalization (≥90th percentile), and inflation-adjusted hospital costs. Multivariable survey-weighted regression models adjusted for demographics, socioeconomic status (SES), comorbidity burden, illness severity, admission type, hospital characteristics, procedure type, and year. Results: An estimated 17,115 hospitalizations were identified, increasing by 26% from 2016 to 2021 (P < 0.001). Overall in-hospital mortality was 1.5%. After adjustment, female sex was associated with lower odds of mortality, while Black race and higher SES were associated with higher adjusted odds of mortality, potentially reflecting referral patterns and case complexity. Median LOS was 5 days, with most admissions lasting ≤5 days. Total inflation-adjusted inpatient costs exceeded $1.7 billion, with disproportionate costs driven by surgical admissions and prolonged hospitalizations. Right hemicolectomy was the most common intervention (52%), whereas CRS/HIPEC was captured in 13% of hospitalizations, acknowledging potential under-representation in administrative data. No significant demographic differences were observed in adjusted odds of undergoing appendectomy or hemicolectomy. Conclusions: Hospitalizations for appendiceal adenocarcinoma increased substantially from 2016 to 2021, while inpatient mortality remained low but varied across demographic groups. Inpatient care was associated with substantial resource utilization, and CRS/HIPEC was infrequently recorded in this national cohort. These findings highlight rising inpatient burden and demographic variation in outcomes, supporting the need for optimized referral pathways and equitable access to specialized care.