Survival of high-grade neuroendocrine carcinomas (HGNEC) of the colon and rectum: Analysis of the Surveillance, Epidemiology, and End Results (SEER) database.

3541 Background: HGNECs are rare, aggressive colorectal tumors, biologically similar to small cell lung cancer. Their optimal management is unclear and based on case series. Our study sought to compare survival outcomes and the role of surgery in HGNECs and high-grade adenocarcinomas (AC) using the population-based SEER registry. Methods: We obtained data on patients (pts) with colorectal HGNEC or AC diagnosed between 1998 and 2011. Relative survival (RS) was the primary endpoint. Trends in incidence and survival were calculated as annual percent change (APC). Associations with prognostic factors and treatment were analyzed in multivariate proportional hazard models, accounting for immortal time bias, and reporting hazard ratios (HR) with 95% confidence intervals (CI). Results: Compared with AC (N=392,854), HGNECs (N=1,455) were more often metastatic (18% vs. 54%, respectively) and more commonly located in the cecum or rectum, but rarely in the sigmoid (P<.0001). The incidence of HGNEC increased during th...