Radioembolization with yttrium-90 resin microspheres for neuroendocrine tumor liver metastases

PURPOSE We aimed to evaluate the effectiveness and safety of radioembolization with yttrium-90 (Y-90) microspheres in cases with unresectable neuroendocrine tumor liver metastases (NETLMs). METHODS Thirty patients (mean age, 55 years) underwent resin-based Y-90 radioembolization for unresectable NETLM at a single institution between April 2008 and June 2013. Post-treatment tumor response was assessed by cross-sectional imaging using the Response Evaluation Criteria in Solid Tumors (RECIST). Prognostic variables that affected survival were determined. RESULTS The mean follow-up was 23.0 +/- 19.4 months and the median overall survival was 39 months (95% CI, 12.6-65.4 months), with one- and two-year survival rates of 71% and 45%, respectively. Imaging follow-up using RECIST at three-month intervals demonstrated partial response in 43%, complete remission in 3%, stable disease in 37%, and progressive disease in 17% of patients. Extent of tumor involvement was found to have a statistically significant influence on overall survival (P = 0.03). The existence of extrahepatic disease at the time of radioembolization, radiographic response, age, and primary neuroendocrine tumor site were not significant prognostic factors. CONCLUSION The current study demonstrates the effectiveness and safety of radioembolization for the treatment of unresectable NETLMs. We identified that the extent of tumor involvement has a significant effect on overall survival. The use of imaging methods reflecting metabolic activity or cellularity such as scintigraphy or diffusion-weighted MRI would be more appropriate, for the response evaluation of liver metastases after radioembolization.