Biological characteristics and treatment outcomes of metastatic or recurrent neuroendocrine tumors: tumor grade and metastatic site are important for treatment strategy

Background: Studies about the biology, treatment pattern, and treatment outcome of metastatic/recurrent neuroendocrine tumor (NET) have been few. Methods: We enrolled patients with metastatic/recurrent NET diagnosed between January 1996 and July 2007 and retrospectively analyzed. Results: A total of 103 patients were evaluated. Twenty-six patients (25.2%) had pancreatic NET, 27 (26.2%) had gastrointestinal NET, 2 (1.9%) had lung NET, 28 (27.2%) had NET from other sites, and 20 (19.4%) had NET from unknown origin. The liver was the most common metastatic site (68.9%). Thirty-four patients had grade 1 disease, 1 (1.0%) had grade 2 disease, 15 (14.6%) had grade 3 disease, 9 (8.7%) had large cell disease, and 7 (6.8%) had small cell disease. Sixty-six patients received systemic treatment (interferon, somatostatin analogues or chemotherapy), 64 patients received local treatment (TACE, radiofrequency ablation, metastasectomy, etc.). Thirty-six patients received both systemic and local treatments. Median overall survival (OS) was 29.0 months (95% confidence interval, 25.0-33.0) in the 103 patients. OS was significantly influenced by grade (p = .001). OS was 43.0, 23.0, and 29.0 months in patients who received local treatment only, systemic treatment only, and both treatments, respectively (p = .245). The median time-to-progression (TTP) was 6.0 months. Overall response rate was 34.0% and disease-control rate was 64.2%. TTP was influenced by the presence of liver metastasis (p = .011). Conclusions: OS of metastatic/recurrent NET was different according to tumor grade. TTP was different according to metastasis site. Therefore, development of optimal treatment strategy based on the characteristics of NET is warranted.