Long-Term Outcomes of Phase 1 and 2 Studies of SBRT for Hepatic Colorectal Metastases
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PURPOSE: To report mature outcomes of prospective phase 1 and 2 studies of stereotactic body radiation therapy (SBRT) for the treatment of colorectal liver metastases (CLMs). METHODS AND MATERIALS: Patients with histologically confirmed CLMs unsuitable for resection or standard therapies were eligible for sequential phase 1 and 2 studies conducted from 2003 to 2012. RESULTS: Of 60 patients treated, 82% had received previous chemotherapy, 23% had undergone previous focal liver treatment, and 38% had extrahepatic disease at the time of SBRT. The median number of gross tumor volume (GTV) targets per patient was 1 (range, 1-6), with a median total target volume of 117.7 cm3 (range, 6.7-3115.4 cm3). The median minimum dose to the GTV was 37.6 Gy (range, 22.7-62.1 Gy) in 6 fractions over a period of 2 weeks. Other than 1 case of grade 3 nausea, there were no acute toxicities greater than grade 2. With a median follow-up period of 28.1 months for survivors, no gastrointestinal bleed or biliary or liver toxicity was seen. The local control rate per lesion at 1 and 4 years was 49.8% and 26.2%, respectively. Increasing minimum dose to the GTV was associated with improved local control (P=.003). Median overall survival was 16.0 months (95% confidence interval, 11.9-20.5 months). On multivariate analysis, improved survival was associated with smaller total GTV (P=.017), performance status of 0 or 1 (P=.007), no extrahepatic disease at the time of treatment (P=.005), and local control of targeted liver disease (P=.001). Two long-term survivors remain disease free at 49 and 125 months. CONCLUSIONS: Six-fraction SBRT for CLM is safe and may be associated with long-term cure. Local control was significantly associated with delivered dose and was lower than seen in other studies using a higher SBRT dose. Survival was associated with smaller tumor volume, absence of extrahepatic disease, performance status of 0 or 1, and local control of treated liver lesions.