SUN-626 Survival of Patients with Gastroenteropancreatic Neuroendocrine Tumors and Diabetes Mellitus in a Seer-Medicare Cohort

Background: The incidence and prevalence of gastroenteropancreatic neuroendocrine tumors (GEP-NET) is increasing globally and has been associated with diabetes mellitus (DM). In this study we aimed to compare tumor characteristics, disease-specific survival (DSS) and overall survival (OS) of GEP-NET patients (pts) with and without DM. Methods: Using the Surveillance, Epidemiology, and End Results registry (SEER) linked to Medicare claims, we identified pts diagnosed with GEP-NET between January 1995 and December 2010, aged ≥65 years at the time of GEP-NET diagnosis. We included patients who were in exclusive Medicare coverage without healthcare management organizations and had Medicare Parts A and B coverage for ≥1year after GEP-NET diagnosis or until death. Within the pts with GEP-NET diagnosis, we identified those without a diagnosis of DM prior to the GEP-NET diagnosis. We compared baseline sociodemographics, co-morbidities, and GEP-NET location, stage, grade and treatment between pts with and without DM using χ (2) analysis. Kaplan Meier (KM) curves were used to compare OS and DSS up to 10 years between the DM and non-DM groups. We used Cox proportional hazards analysis to compare the DSS between the groups, adjusting for confounding variables. Results: We identified a cohort of 1,969 well-characterized GEP-NET patients with accurate tumor stage, grade, comorbidities, and treatment data. 478 (25.7%) had DM and 1,383 (74.3%) did not have DM. There were no statistically significant differences in gender or age at the time of GEP-NET diagnosis in the DM (mean age 74.7±SD 6.6 yrs) and non-DM (74.9±7.4 yrs) groups. Significant differences in race were found in the DM (80.6% white, 13.6% black, 1.3% hispanic) and non-DM (86.8% white, 8.2% black, 1.8% Hispanic) groups (p=0.002). Patients with DM had more gastric (14.7%), duodenal (10.9%) and pancreatic (21.0%), and less jejunal/ ileal (12.8%) NETs compared with the non-DM group (9.7%, 6.4%, 16.9%, 18.2%, respectively, p<0.0001). Patients with DM had earlier stage disease than those without DM (p=0.0012), but no difference in tumor grade or treatment was found. KM curves revealed no differences in OS and DSS in the GEP-NET patients with and without DM across all stages. Multivariate adjusted Cox proportional-hazards model found no significant difference in DSS between those with and without DM (HR=0.97, 95%CI: 0.76–1.24). Compared with pts with pancreatic NETs, pts with colon (HR=1.39, 95%CI: 1.04–1.86) had worse survival, while those with jejunal/ileal (HR = 0.59, 95%CI: 0.42–0.83) NETs had a better survival. Discussion: This is the first study to investigate the effect of DM on survival of pts GEP-NETs. We found a high prevalence of pre-existing DM in pts with GEP-NETs, but no difference in OS or DSS in pts with and without DM. Interestingly, pts with DM had more foregut GEP-NETs which may suggest mechanistic links between DM and GEP-NETs at these sites.