Stereotactic body radiotherapy for colorectal cancer liver metastases: A systematic review

While surgery is the preferred option for isolated, operable liver metastases from colorectal cancer (CRC), ablative techniques are endorsed for medically or technically inoperable lesions. Stereotactic body radiotherapy (SBRT) is an alternative ablative local therapy that delivers high RT doses in a few fractions to the cancer, sparing surrounding critical tissue. We have performed a systematic review of published trials to evaluate the efficacy of SBRT as a primary modality therapy for CRC liver oligometastases.

We searched the Cochrane Central Register of Controlled Trials, Pubmed, and EMBASE for publications regarding SBRT for CRC liver metastases. Overall survival (OS: median, 1- and 2-year OS %) was the primary endpoint, and median PFS and one- and two-year local control (LC) were the secondary endpoints. A random-effect model pooled-analysis was performed to calculate the aggregated OS rates at 1 and 2 years as well as the one- and two-year LC.

A total of 18 studies, encompassing 656 patients, were included in the analysis. The pooled one- and two-year OS were 67.18% (95% CI, 42.1-92.2) and 56.5% (95% CI, 36.7-76.2), respectively. Median PFS and OS were 11.5 and 31.5 months. The pooled one-year LC was 67% (95% CI, 43.8-90.2), while the pooled two-year LC was 59.3% (95% CI, 37.2-81.5). Correlation analysis revealed a moderate/poor linear relationship between the SBRT (BED10) dose and LC (p = 0.001, R = 0.47)/OS (p = 0.001, R = 0.29) at 2 years. Mild-moderate and severe liver toxicity were 30.7% and 8.7%.

SBRT for liver oligometastases is an effective option for patients with advanced CRC, with encouraging local control and survival. However, a definitive validation in large randomised studies is required, due to the retrospective or non-randomised nature of the included studies and the limitations of series with different doses/schedules of treatment.