Selective Internal Radiation Therapy (SIRT): a new emerging role for Breast Cancer Liver Metastases

Background: Breast cancer is one of the leading causes of death worldwide. Approximately 50% of patients (pts) with metastatic breast cancer develop liver metastases and liver represents the first metastatic site in 5-12%. Breast cancer liver metastasis (BCLM) heralds a poor prognosis and unfortunately the vast majority are unresectable at the time of diagnosis. Median survival of patients with unresectable chemoresistant BCLM is 3 to 10 months. SIRT is a locoregional treatment based on the administration of radioactive yttrium (90Y) microspheres directly into the tumor vasculature and has been advocated as an option for target hepatic lesions, minimizing side effects. While its benefit is widely demonstrated in colon-rectal cancer, less is known about its clinical efficacy in breast cancer. Materials and Methods: We performed a retrospective observational study including pts with diagnosis of BCLM treated with SIRT after a multidisciplinary discussion at the Oncology Department of Sapienza University in Rome. We collected clinicopathological characteristics from clinical records and analyzed their relation with overall survival (OS) and progression free survival (PFS) post SIRT. Results: We enrolled 34 pts (33 women; 1 man). Median age at SIRT was 49 years old (range 71-32). 82% had hormone receptor-positive (HR+) and 18% HER2-positive breast cancer. 47% had extra-hepatic disease. 85% pts had an optimal Performance Status (PS)=0 at SIRT time and only 35% had a PS⩾1; Response to SIRT was evaluated with PET-FDG or CT-scan with a complete response in 44% pts, partial response or stable disease in 44% and progression disease in 12%. MedianOS (mOS) after SIRT was 14,5 months while medianPFS (mPFS) hepatic and extra hepatic after SIRT were 6 months and 6,5 months respectively. Correlation between mOS and mPFS was statistically significant with Pearson’s (p<0.01). No statistically significant differences were seen for molecular subtype. Finally in pts who underwent SIRT as II or III line therapies (38%) we found a mPFS of 12 months vs 7 months in those who underwent SIRT in subsequent lines (62%) (p=0.5). Conclusions: Considering our data and the limited benefit obtained with available therapies for BCLM in advanced lines of treatment, SIRT represents a valid therapeutic option when used in prior lines. We still need to identify the right clinical timing and criteria for a better patient selection.