Clinicopathological factors related to survival in gastroenteropancreatic neuroendocrine tumors (GEP-NET): 20 years experience in the American British Cowdray Medical Center.

656 Background: Neuroendocrine neoplasms (NEN) are a diverse group of tumors originating from neuroendocrine cells found throughout the body. Their “rarity”, heterogeneity, and non-specific presentation contribute to limited reliable epidemiological data, especially in developing countries such as Mexico. This study aims to analyze the clinical and pathological features of gastroenteropancreatic neuroendocrine tumors (GEP-NET) and their association with survival in a third-level center in Mexico. Methods: A retrospective cohort study at the American British Cowdray Medical Center, in Mexico City, was conducted. We included all histopathological confirmed GEP-NET from 2004 to 2024. Clinical, biochemical, and radiological features at diagnosis were analyzed. Survival was estimated using Kaplan-Meier and Log-Rank test. Results: We identified 110 NENs, of which 89% were GEP-NET, 56.1% were female, and the median age was 57.7 (SD 13.8) years. The clinical stage was metastatic (50%), localized (37.7%), and locally advanced (6.1%). The primary sites were the pancreas (49%), small bowel (23.5%), gastric (10.2%), colon (7.1%), rectum (5.1%), appendix (3.1%), and unknown (2%). ECOG performance status were 0-1 in 96.9%. In the metastatic setting, liver involvement was 96.2%, mainly high hepatic burden (59.6%). Symptoms were abdominal pain (34.6%), diarrhea (16.3%), and bowel obstruction (6.1%). Functioning tumors were 26.8%, and carcinoid syndrome was found in 9.2%. Grades 1, 2, and 3 were 62.9%, 34%, and 3.1% respectively. The median of Ki-67 was 6.4%. At diagnosis, Ga-68 PET/CT scan, serum CgA, and urinary 5-HIIA were performed in 98.2%, 39.7%, and 16.3% of patients. Among metastatic patients, 87.1% received at least one line of systemic treatment, primarily with somatostatin analogs (62.9%). In all population, the median follow-up was 42.5 months and the median overall survival (OS) was 164.9 (SD 12.2) months. Univariate analyses showed that primary site (p=0.02), Ki-67 <5% (p=0.02), CgA <700 ng/ml (p=0.03), and low hepatic burden (p=0.01) were statistically significantly associated with OS. Conclusions: This study provides critical insights into GEP-NET characteristics in a Mexican population, highlighting clinical, biochemical, and radiological factors associated with better survival.