Factors Predicting Response and Survival After Yttrium-90 Radioembolization of Unresectable Neuroendocrine Tumor Liver Metastases

Yttrium-90 (90Y) radioembolization is a promising treatment option for unresectable neuroendocrine tumor liver metastases (NETLM). This study is the first to evaluate the prognostic variables that influenced radiologic response and survival in patients with unresectable NETLM who were treated with 90Y radioembolization. As a secondary outcome, the impact of this treatment on serologic toxicity was assessed.Forty-eight patients underwent resin-based 90Y radioembolization for unresectable NETLM at a single institution between December 2003 and May 2009. Patients were assessed radiologically and serologically at 1 month and then at 3 month intervals after treatment. Prognostic variables that affected response and survival were determined. The impact of this treatment on serologic toxicity over a 6-month period was assessed.No patient was lost to follow-up. The median follow-up for the patients who were alive was 41 months. The median survival was 35 months (range: 5-63). On imaging follow-up, 7 patients (15%) had a complete response and 19 patients (40%) had a partial response to treatment. Eleven patients (23%) had stable disease and 11 patients (23%) had progressive disease. Five prognostic factors were associated with an improved survival: complete/partial response (P=0.003), low hepatic tumor burden (P=0.022), female gender (P=0.022), well-differentiated tumor (P=0.001), and absence of extra-hepatic metastasis (P<0.001). Three factors were associated with a complete/partial response: female gender (P=0.040), well-differentiated tumor (P<0.001) and low hepatic tumor burden (P=0.041). There was a significant increase in the level of alkaline phosphatase over the 6-month period (P<0.001).90Y radioembolization is a promising treatment option for unresectable NETLM. Patients with low hepatic tumor burden, well-differentiated tumor, female gender, and no extrahepatic disease benefit most from treatment.