Stereotactic Body Radiation Therapy With Ablative Dose on Liver Metastases: Radiation-induced Liver Disease (RILD) and Toxicity Assessment

Purpose/Objective(s): To assess the safety of high-dose stereotactic body radiation therapy (SBRT) with volumetric modulated arc therapy (VMAT) technique for the treatment of patients with unresectable liver metastases from solid tumors, with special regard on liver function. Materials/Methods: Patients with 1 to 3 unresectable liver metastases with maximum individual tumor diameters less than 6 cm, a Karnofsky Performance Status of at least 70 and life expectancy more than 6 months were enrolled and treated by SBRT on a phase II clinical trial. Dose prescription to mean clinical target volume (CTV) was 75 Gy in 3 consecutive days, with planning target volume (PTV) covered by at least the isodose of 67%, and where possible, this limit on PTV was increased up to 95% of the prescription. When the dose constraints for normal tissues could not be fulfilled, dose reduction up to 30% was allowed. SBRT was administered using VMAT technique by RapidArc, with a flattening filterfree photon beam 10 MV (FFF) and maximum dose rate of 2400 MU/min. Results: Between February 2010 and August 2011, 57 patients with 77 lesions were enrolled in this trial. Among them, 21% had extrahepatic disease at the time of SBRT. Primary tumor sites were colon in 24, breast in 19, bilio-pancreatic in 6, uterus in 5, and others in the remaining 17. Seventyfour (74%) of patients had 1 lesion, 19% and 7% of patients had 2 and 3 lesions, respectively. Sixty-three lesions (82%) were treated with a full dose of 75 Gy. Dose reduction was provided in only 14 lesions to respect the dose constraints. Mean beam-on time was 2.9 1.5 min (range, 1.9-6.2 min). None of the patients experienced grade 3 or higher acute toxicity. Grade 2 acute toxicity, mainly gastrointestinal, occurred in 7 patients (14%). No radiation-induced liver disease (RILD) was detected. Given the short length of follow-up, no data on late toxicity are currently available. Conclusions: Findings suggest that SBRT for unresectable liver metastases is associated with a low incidence of acute toxicity, and can be considered as a safe and noninvasive therapeutic option in this setting.