Local Control Outcomes Using Stereotactic Body Radiation Therapy for Liver Metastases From Colorectal Cancer

Purpose To evaluate the effective dose and patterns of recurrence after stereotactic body radiation therapy (SBRT) for hepatic metastases that arise from colorectal cancer. Methods and Materials A cohort of 70 patients with 103 colorectal liver metastases were treated with SBRT at a single institution. The prescribed doses were 45 to 60 Gy in 3 to 4 fractions, but these were modified according to the tolerance of the adjacent normal tissue. To allow for dose comparisons, a biological equivalent dose was calculated. Results The median follow-up period was 34.2 months (range, 5.3-121.8 months). The 2-year overall survival and progression-free survival rates were 75% and 35%, respectively. In subgroups, the 2-year local control rates for biological equivalent dose ≤80 Gy (group 1), 100 to 112 Gy (group 2), and ≥132 Gy (group 3) were 52%, 83%, and 89%, respectively. Cox proportional hazards model revealed a significant difference between groups (hazard ratio 0.44, P=.03 for group 2; hazard ratio 0.17, P=.17 for group 3; P=.01 for total). The major pattern of failure was a new liver metastasis out of the SBRT field. There was no grade ≥3 toxicity. Conclusions Stereotactic body radiation therapy of liver metastases derived from colorectal cancer offers a locally effective treatment without significant complications. Longer local control can be expected if higher doses are used. Further studies will be needed to compare the efficacies of SBRT with those of surgical resection or radiofrequency ablation.