Yttrium-90 for the treatment of breast cancer liver metastases: a global propensity-matched study.

Background: Breast cancer is the most common malignancy in women. Despite advancements in monoclonal antibodies and targeted therapies, the prognosis significantly worsens once distant metastases develop. Y-90's benefit for breast cancer liver metastasis (BCLM) patients is largely understudied, as prior retrospective studies have been limited in their cohort size. We evaluated the impact of Y-90 radioembolization on overall survival in BCLM patients in a diverse multi-institutional cohort. Methods: A retrospective cohort study was conducted using the TriNetX Research Network comparing Y-90 and non-Y-90 BCLM cohorts. The primary endpoint was overall survival, measured at 3, 6, 9, and 12 months. A total of 25,730 patients were screened for potential inclusion in the study. After propensity-score matching for age, race, and ethnicity, 221 patients were included in each cohort. Results: At 3, 6, and 9 months, the Y-90 cohort demonstrated a significantly lower mortality risk compared to the non-Y-90 cohort. At 12 months, the mortality risk was statistically similar between the two arms. Conclusion: Y-90 treatment is associated with significantly improved survival out to at least 9 months, providing further evidence for its utility in antitumor efficacy. For patients who have liver-predominant disease or liver-only progression, treatment with Y-90 should be considered a reasonable treatment option.