Background: This study aimed to determine whether postoperative chemotherapy is associated with a survival benefit for patients with poorly differentiated neuroendocrine carcinoma (NEC) of the stomach, small bowel, or pancreas.
Methods: Patients were identified in the National Cancer Database (NCDB) between 2004 and 2014. Inverse probability of treatment weighting (IPTW) was used to reduce selection bias. To compare the overall survival (OS) of patients in different treatment groups, IPTW-adjusted Kaplan-Meier curves and Cox proportional hazards models were used.
Results: The inclusion criteria were met by 759 patients. The diagnosis was NEC of the stomach for 195 patients (25.7%), NEC of the small intestine for 278 patients (36.6%), and NEC of the pancreas for 286 patients (37.7%). Overall, 213 patients (28.1%) received postoperative chemotherapy after curative resection. For the patients who received chemotherapy, IPTW-adjusted survival showed no OS benefit. However, subgroup analysis demonstrated improved OS with observation (OB) for patients with NEC of the small intestine (hazard ratio [HR], 1.436; 95% confidence interval [CI] 1.13-1.823; P = 0.003), T3 or T4 primary tumor (HR, 1.258; 95% CI 1.08-1.465; P = 0.003), node-positive disease (HR, 1.238; 95% CI 1.040-1.475; P = 0.0165), or positive resection margin (HR, 1.4283; 95% CI 1.02-2.00; P = 0.038).
Conclusions: In this national database analysis, postoperative chemotherapy was not associated with improved survival for patients with poorly differentiated gastroenteropancreatic (GEP) NECs. These findings highlight the need for continued efforts to understand better which patients in this high-risk population will benefit from additional systemic therapy and the need for continued development of more effective therapies for these patients.