574 - Efficacy of Radiation Segmentectomy for Treatment of Breast Cancer Liver Metastases

Purpose: Breast cancer remains the second most common cancer globally and the leading cause of cancer-related death among females worldwide. Treatment options for patients with liver metastases from breast cancer are limited and prognosis remains poor. Radioembolization is a promising treatment for patients however there is a lack of ideal dosimetry techniques specific for breast cancer. The benefit of targeted high dose selective internal radiation therapy has been established for treatment in hepatocellular cancer and other malignancies however there is limited information on use in breast cancer. This study examines the clinical outcomes of patients with oligometastatic liver metastases following treatment with radiation segmentectomy.

Materials and Methods: This is an IRB approved retrospective review. From March 2021 – July 2024, a total of 30 patients with breast cancer with olivomegastatic liver disease underwent radiation segmentectomy. Demographic information, cancer status, receptor status, and number of lines of prior chemotherapy were assessed. Treatment consisted of 1-2 sessions of selective administration of yttrium-90 glass microspheres with a minimum prescribed target dose of 200Gy using MIRD or personalized dosimetry models. Clinical efficacy was evaluated using RECIST and PERCIST criteria at 3 months, 6 months and 1 year following initial treatment.. Safety parameters evaluated were pre and post procedure liver chemistry, MELD and ALBI scores. Adverse events were monitored. The achieved doses were assessed using retrospective voxel analysis of post treatment SPECT/CT.

Results: Procedure was technically successful in 100% of patients. 0 serious adverse events were encountered. 6 of 30 patients encountered a transient increase in total bilirubin. Objective response was seen in 28 of 30 (93.3%) patients. 100% of patients that achieved a target dose of 200 Gy experienced objective response. 10 of 30 (33%) patients had a complete response of the target lesion. 12 of 30 (40%) patients had progression of disease in non-targeted area of the liver at 12 months. The 1 year overall survival was 27 of 30 (90%). Lesions less than 6cm were significantly more likely to have an objective response p< 0.01 or complete response p< 0.001. Achieved target dose was associated with higher ORR and CR.

Conclusion: Radiation segmentectomy for treatment of breast cancer liver metastases is safe and effective at a minimum target tumor dose of 200 Gy.