BACKGROUND : The objective of the current study was to determine the safety and efficacy of Yttrium-90 (Y90) microsphere treatment in patients with liver-dominant colorectal metastases. METHODS : Seventy-two patients with unresectable hepatic colorectal metastases were treated at a targeted absorbed dose of 120 Gray (Gy). Safety and toxicity were assessed using version 3 of the National Cancer Institute Common Terminology Criteria. Response was assessed by anatomic imaging and positron emission tomography (PET). Survival from the diagnosis of hepatic metastases and first treatment were estimated using the Kaplan-Meier method. Substratification analyses were performed. RESULTS : The median dose delivered was 118 Gy. Treatment-related toxicities included fatigue (61%), nausea (21%), and abdominal pain (25%). Grade 3 and 4 bilirubin toxicities were observed in 9 of 72 patients (12.6%). The tumor response rate was 40.3%. The median time to hepatic progression was 15.4 months, and the median response duration was 15 months. The PET response rate was 77%. Overall survival from the first Y90 treatment was 14.5 months. Tumor replacement (< or =25% vs >25%) was associated with significantly greater median survival (18.7 months vs 5.2 months). The presence of extrahepatic disease was associated negatively with overall survival (7.9 months vs 21 months). Overall survival from the date of initial hepatic metastases was 34.6 months. A subset analysis of patients who had an Eastern Cooperative Oncology Group performance status of 0 demonstrated a median survival of 42.8 months and 23.5 months from the time of hepatic metastases and Y90 treatment, respectively. CONCLUSIONS : Y90 liver therapy appears to provide sustained disease stabilization with acceptable toxicity. Asymptomatic patients with preserved liver function at the time of Y90 appeared to benefit most from treatment. Cancer 2009. (c) 2009 American Cancer Society.