Association of inpatient outcomes with carcinoid syndrome among malignant neuroendocrine tumor hospitalizations in the United States: NIS 2016–2022.

e16320 Background: Carcinoid syndrome (CS) may contribute to inpatient morbidity and resource utilization among patients with neuroendocrine tumors (NETs). However, contemporary national-level data describing the inpatient burden, complications, and outcomes associated with CS remain limited. We aimed to characterize national inpatient trends and assess outcomes associated with CS in malignant NET hospitalizations. Methods: Adult hospitalizations in the National Inpatient Sample (NIS) 2016–2022 with malignant NET diagnoses (ICD-10-CM C7A*/C7B*) were identified. CS was defined by any-diagnosis E34.0*. Survey weights and design-based variance estimates were applied. Outcomes included in-hospital mortality, complications, length of stay (LOS), and total charges (TOTCHG). Survey-weighted regression adjusted for demographics, socioeconomic/hospital factors, calendar year, payer, and key complications (sepsis, septic shock, acute kidney injury [AKI], acute respiratory failure, palliative care). Results: Among 33,318 NET hospitalizations (weighted n = 166,590), 3.24% had CS. Compared with non-CS hospitalizations, CS hospitalizations were older (66.1 vs 64.5 years), more often female (55.3% vs 51.2%), and more often Medicare-insured (62.1% vs 55.3%). AKI was more frequent with CS (30.6% vs 21.0%; P < 0.001), while sepsis and acute respiratory failure rates were similar. Unadjusted mortality was higher with CS (7.14% vs 5.55%), but CS was not independently associated with mortality after adjustment (aOR 1.19, 95% CI 0.90–1.58). CS was independently associated with longer LOS (+0.51 days) and higher charges (+$11,172). CS prevalence did not significantly vary by year. Conclusions: CS was present in ~3% of malignant NET hospitalizations and was associated with increased AKI and independently higher LOS and charges, without an independent association with in-hospital mortality after adjustment. Prospective studies are needed to clarify causal pathways and evaluate targeted inpatient interventions to prevent renal injury and reduce resource utilization.