Primary Gallbladder Neuroendocrine Tumors: Insights into a Rare Histology Using a Large National Database

Background: Primary gallbladder neuroendocrine tumors (NETs) are rare, poorly understood cancers infrequently encountered at even the largest of tertiary referral centers. We therefore sought to identify a large cohort of patients with gallbladder NETs using a national database, with the aim of defining treatment modalities employed and survival associated with these uncommon malignancies. Methods: Patients with primary gallbladder NETs were identified in the National Cancer Database, and clinicopathologic characteristics were recorded. A univariate log-rank survival analysis was completed for patients who underwent resection. Parameters found to be significant were entered into a multivariate accelerated failure time analysis. For context, survival comparisons were included for patients who underwent resections for NETs at any gastrointestinal site and for gallbladder adenocarcinoma. Results: Overall, 754 patients with gallbladder NETs were identified. Patients were predominantly female (n = 518, 69%), White (n = 503, 67%), presented with stage IV disease (n = 295, 39%) and had high-grade lesions (n = 312, 41%). The majority underwent resection (n = 480, 64%), primarily simple cholecystectomy (n = 431, 90%), whereas a minority received multimodal therapy (n = 145, 21%). Among patients who underwent resection, older age (p = 0.001), large cell histology (p = 0.012), and positive margins (p = 0.030) were independently associated with worse overall survival. Patients with gallbladder NETs had improved survival relative to those with gallbladder adenocarcinoma (p = 0.001), but significantly worse survival than patients with NETs from other gastrointestinal sites (p < 0.001). Conclusions: Primary gallbladder NETs are aggressive lesions that carry a worse prognosis than NETs of other gastrointestinal sites. Older age, positive margins, and large cell histology are associated with abbreviated survival after resection.