Nisha, Fnu

e22593 Background: Pheochromocytoma is a rare neuroendocrine tumor, and population-level data describing long-term temporal trends are limited. Evaluating national patterns over time may improve epidemiologic understanding and clinical awareness. Methods: We performed a retrospective analysis of pheochromocytoma cases recorded in the Surveillance, Epidemiology, and End Results (SEER) database from 1975 through 2022. Annual case counts were examined overall and by race (White, Black, Other, and Unknown). Temporal trends were assessed using Poisson regression, and annual percent change (APC) was calculated to quantify changes over time. Results: A total of 408 pheochromocytoma cases were identified during the study period. Overall case counts increased significantly over time, with Poisson regression demonstrating a consistent upward trend corresponding to an APC of 5.8% per year (p < 0.001). White individuals accounted for the majority of reported cases, while Black and other racial groups had significantly lower case counts compared with the reference population. Visual assessment of decade-level trends suggested a gradual increase from 1975 through approximately 2010, followed by a sharper rise in more recent years. Conclusions: Pheochromocytoma case counts in the United States have increased substantially over the past five decades based on SEER data. These findings suggest evolving epidemiologic patterns in this rare tumor and emphasize the importance of continued surveillance. Observed trends should be interpreted in the context of potential changes in diagnostic practices, imaging utilization, and cancer registry reporting over time.

e16322 Background: Small intestine neuroendocrine carcinoma (NEC) is a rare, aggressive malignancy comprising less than 0.1% of gastrointestinal cancers. Population-level data remain limited, restricting understanding of long-term survival patterns, demographic disparities, and evolving disease burden. We evaluated survival outcomes, demographic predictors, and incidence trends of small intestine NEC in the United States. Methods: We conducted a retrospective population-based cohort study using SEER Research Data (17 registries, November 2024 submission). Patients diagnosed with malignant small intestine NEC (ICD-O-3 morphology code 9.3.3.1.2) between 2000 and 2022 were identified using SEER*Stat (v9.0.4.2). Variables including age group, sex, race, year of diagnosis, survival time, and vital status were analyzed in R (v4.5.1). Overall survival (OS) was estimated using Kaplan–Meier methods and compared using log-rank testing. Cox proportional hazards models identified independent predictors of OS. Annual case counts were modeled using time-series forecasting to project future incidence. Results: A total of 506 patients were included. Estimated OS was 94.4% (95% CI 92.4–96.4) at 1 year, 88.1% (85.3–91.0) at 3 years, and 82.4% (79.0–85.9) at 5 years, with a subset demonstrating survival beyond 15 years. Increasing age was associated with worse survival (log-rank p = 0.058). Significant racial differences in OS were observed (log-rank p < 0.0001). In multivariable analysis, race remained independently associated with OS. Incidence forecasting projected a modest increase in annual case burden over the next decade. Conclusions: Small intestine NEC demonstrates heterogeneous survival outcomes, significant demographic disparities, and projected growth in disease burden. These findings highlight the need for improved risk stratification, equitable access to care, and integration of molecular and treatment-level data to optimize management of this rare malignancy