Is stereotactic body radiation therapy an attractive option for unresectable liver metastases? A preliminary report from a phase 2 trial

Purpose: To evaluate the feasibility of high-dose stereotactic body radiation therapy (SBRT) in the treatment of unresectable liver metastases. Methods and Materials: Patients with 1 to 3 liver metastases, with maximum individual tumor diameters less than 6 cm and a Karnofsky Performance Status of at least 70, were enrolled and treated by SBRT on a phase 2 clinical trial. Dose prescription was 75 Gy on 3 consecutive days. SBRT was delivered using the volumetric modulated arc therapy by RapidArc (Varian, Palo Alto, CA) technique. The primary end-point was in-field local control. Secondary end-points were toxicity and survival. Results: Between February 2010 and September 2011, a total of 61 patients with 76 lesions were treated. Among the patients, 21 (34.3%) had stable extrahepatic disease at study entry. The most frequent primary sites were colorectal (45.9%) and breast (18%). Of the patients, 78.7% had 1 lesion, 18.0% had 2 lesions, and 3.3% had 3 lesions. After a median of 12 months (range, 2-26 months), the in-field local response rate was 94%. The median overall survival rate was 19 months, and actuarial survival at 12 months was 83.5%. None of the patients experienced grade 3 or higher acute toxicity. No radiation-induced liver disease was detected. One patient experienced G3 late toxicity at 6 months, resulting from chest wall pain. Conclusions: SBRT for unresectable liver metastases can be considered an effective, safe, and noninvasive therapeutic option, with excellent rates of local control and a low treatment-related toxicity.