Characterization of a novel entity of high-grade well-differentiated colorectal neuroendocrine tumors.

Abstract

e15696 Background: Small studies suggest that a new pathologic entity of high-grade (by Ki-67 or mitotic index) well-differentiated (by histologic features) neuroendocrine tumors (NETs) exist throughout the GI tract, but the prognosis and characteristics of affected patients are unknown. We sought to further characterize the prognosis and demographics of patients with high-grade (HG) well-differentiated (WD) colorectal NET. Materials and Methods: We used the Surveillance Epidemiology and End Results (SEER) database to study patients with NETs of the colon and rectum diagnosed from 2000 to 2015. We identified patient demographics, clinical and tumor characteristics, and studied associations with tumor grade. We compared overall survival (OS) between patients with low-grade (LG)(grade 1-2) well-differentiated (ICD-0-3 = carcinoid), high-grade (grade 3-4) well-differentiated, and high-grade poorly-differentiated NETs (ICD-0-3 = small cell neuroendocrine). We used logistic regression to detect associations with grade and Cox proportional hazards models to examine predictors of survival. Results: We identified 5,894 cases with colorectal carcinoid tumor (5780 [98.1%] LG and 114 [1.9%] HG); the cohort was 68% white, 48% male, and had a median age of 54. Patients diagnosed with HG carcinoid tumors were more likely to be of older age (OR 2.23; 95% CI 1.19-4.19 for age 60-69 vs < 50) and unmarried (OR 1.56; 95% CI 1.02-2.38), and less likely to be diagnosed after 2010 (OR 0.09; 95% CI 0.06-0.15). OS for patients with HG carcinoids (median 36 m; 95% CI 13-92) fell in between OS for those with HG small cell NETs (median 7 m; 95% CI 6-8), and LG carcinoid tumor (median not reached, > 120 m). Among patients with carcinoid tumors, black patients (HR 1.31; 95% CI 1.03-1.67, older patients (HR 3.60; 95% CI 2.50-5.19 for age 60-69 vs < 50), unmarried patients (HR 1.52; 95% CI 1.24-1.87), and those with HG features (HR 3.85; 95% CI 2.88-5.15) had worse survival. Conclusions: We defined a subset of high-grade well-differentiated NETs, more commonly diagnosed in older, unmarried patients, with a prognosis between that of high grade small cell NETs and low grade carcinoid tumors. Our analysis adds the first national registry study to the literature in support of a new classification of non-pancreatic high-grade well differentiated NETs.