Treatment outcomes of breast cancer liver metastasis treated with stereotactic body radiotherapy.

Background: To assess the outcomes of breast cancer liver metastasis (BCLM) treated with stereotactic body radiotherapy (SBRT) and systemic treatment.

Materials And Methods: Patients with oligometastasis at the time of liver metastasis (LM) or who became oligometastatic (≤5 metastases) after systemic treatment were assessed. Twenty-nine liver metastatic lesions were treated with a total of 54 Gy delivered in 3 fractions. The local control (LC), overall survival (OS), and progression-free survival (PFS) rates were calculated using Kaplan-Meier analyses.

Results: A total of 22 patients with 29 liver metastatic lesions treated with liver SBRT between April 2013 and September 2017 were retrospectively analyzed. After a median follow-up time of 16.0 months (range 4.4-59.4 months), 18 patients (82%) had disease recurrence, median of 7.4 months (range 1.0-27.9 months) after completion of liver SBRT. The 1- and 2-year OS rates were 85% and 57%, and the 1- and 2-year PFS rates were 38% and 8%, respectively. The 1- and 2-year LC rates were 100% and 88%, respectively. No significant prognostic factors, including disease extension, size of metastasis, number of liver metastasis and timing of liver metastasis, hormonal status affecting OS, PFS and LC were found. No patients experienced Grade 4 or 5 toxicity; furthermore, only one patient experienced rib fracture 6 months after completion of treatment, and one patient had a duodenal ulcer.

Conclusion: This study is the first to evaluate the feasibility of SBRT to BCLM patients. Liver SBRT is a conservative approach with excellent LC and limited toxicities.