Robotic stereotactic radiotherapy for liver oligometastases from colorectal cancer: a single-center experience

Purpose To report on the safety and clinical benefit of robotic stereotactic radiotherapy (SBRT) for liver oligometastatic colorectal cancer (CRC). Methods Robotic SBRT was applied to oligometastatic CRC patients, defined as having 1–4 liver metastases and absent or controlled extrahepatic disease. The intended prescription dose was 37.5 Gy in three fractions. Treatment efficacy was estimated by clinical benefit rate (CBR), progression-free survival (PFS) and overall survival (OS). Toxicity was graded according to CTC-AE scale, v. 4.03. Regression analysis was performed to search for the presence of any predictive factors. Results Between 2012 and 2017, 38 patients (66 lesions) were irradiated. The median delivered biological effective maximum dose (maxBED 10 ) was 142 Gy. At a median follow-up of 11.8 months (range 3.2–58.8), the 1- and 2-year OS were 67.3% and 44.1%, respectively. Actuarial LC rates for all patients at 6 and 12 months were 64.2% and 60.4%, respectively. Local or distant progression occurred in 28 (77.8%) patients, with a 1- and 2-year PFS of 19.3% and 12.2%, respectively. The CBR was 71.4%, with no significant association with maxBED 10 . At multivariate analysis, the presence of extrahepatic disease had a detrimental impact on PFS (HR 3.98, 95% CI 1.77–8.93; p