Stereotactic body radiation therapy for local control of liver metastases from colorectal cancer.

Abstract

662 Background: Although possible candidates for surgical treatment are increasing, majority of colorectal cancer patients with liver metastases are ineligible for surgery. In our institution, SBRT for liver metastatic colorectal carcinoma has been adopted since 2005. By reviewing the treatment outcomes of relatively large cohorts treated with homogeneous technique, we aimed to report patterns of recurrence and the most effective dose fractionation schedule. Methods: Seventy patients with colorectal liver metastases were treated with SBRT from 2005 to 2014. Total number of treated lesions was 103. Median tumor size was 2.5 cm, with ≥ 3 cm in 42 (41%) lesions. Prescribed doses were biologically equivalent dose (BED) ≥ 112 Gy10, but, if small bowel is adjacent to target volume, dose was decreased according to the normal tissue tolerance dose. Prescription doses relevant to BED ≥ 112 Gy10 were ≥ 45 Gy in 3 fractions or ≥ 60 Gy in 5 fractions, in this study. Results: Median follow-up period was 34.2 months (range, 5.3-121.8). The 2-year local control rate was 92% when full prescription dose was delivered, and 73% if compromised dose group was included. On prognostic factor analysis for local control, N-stage (P= 0.008), and BED (P= 0.001) were significant factors. Overall survival rate was 86% for BED ≥ 112 Gy10 group, and 73% for total cohort. The major pattern of failure was out-of-field intrahepatic progression. On multivariate analysis, N stage (P= 0.001), lesion size (P= 0.010) and number of treated hepatic lesions (P< 0.001) were significant factors for intrahepatic control. Conclusions: Liver SBRT was an effective treatment option for colorectal liver metastases. If BED ≥ 112 Gy10 was delivered, we could expect long-term survival in substantial portion of patients. Major pattern of failure was out-of-field intrahepatic progression, which was related to number of treated hepatic lesions, lesion size and N-stage.