Clinical Outcomes of Patients with Metastatic Breast Cancer Treated with Hypo-Fractionated Liver Radiotherapy

To retrospectively review the clinical outcomes of patients with metastatic breast cancer (MBCa) following liver directed ablative intent radiotherapy (RT). Demographics, disease and treatment characteristics of patients with MBCa who received liver metastasis (LM) directed ablative RT between 2004-2020 were analysed. The primary outcome was local control (LC), secondary outcomes included overall survival (OS) and progression-free survival (PFS) analyzed by univariate (UVA) and multi-variable analysis (MVA). Thirty MBCa patients with 50 LM treated with 5-10 fraction RT were identified. Median follow-up was 14.6 (range 0.9-156.2) months. Class of metastatic disease was described as induced (12 patients, 40%), repeat (15 patients, 50%) and de novo (three patients, 10%). Median size of treated LM was 3.1 cm (range 1-8.8 cm) and median biologically effective dose delivered was 122 (Q1-Q3; 98-174) Gy . One-year LC rate was 100%. One year and two-year survival was 89% and 63%, respectively, with size of treated LM predictive of OS (HR 1.35, = 0.023) on UVA. Patients with induced OMD had a significantly higher rate of progression (HR 4.77, = 0.01) on UVA, trending to significance on MVA (HR 3.23, = 0.051). Hypo-fractionated ablative liver RT in patients with MBCa provides safe, tolerable treatment with excellent LC.