Radiation therapy in the management of breast cancer brain metastases: the impact of receptor status on treatment response, intracranial recurrence, and survival

Objective: Breast cancer is the second most common cancer to metastasize in the brain. Little is known about how receptor subtype, including luminal A, luminal B, human epidermal growth factor receptor 2 (HER2) enriched, and triple negative (TN) affect response to radiation and distant intracranial recurrence (ICR) following radiation therapy. Methods: We conducted a single-institution retrospective analysis of 38 breast cancer brain metastasis (BCBM) patients who underwent 93 treatment courses of stereotactic radiosurgery, stereotactic radiotherapy, post-operative radiation, or whole brain radiation therapy. Endpoints included overall survival (OS), treatment response (partial/complete response, PR/CR, or progression), ICR after treatment, and time from breast cancer diagnosis to the first BCBM (time to metastasis, TTM). Subset analyses were performed for triple receptor subtype as well as estrogen receptor (ER) positive versus negative, HER2+ versus HER2-, and age ≤ 50 versus >50 years old. Results: Median OS for the population was 22.5 months, with median follow-up after treatment of 20.5 months. TTM was shortest for HER2 enriched, TN, ER−, and younger patients. TN, HER2-, and younger patients showed the poorest OS. ICR was also greatest in TN and HER2− patients. Radiation failure at the treated BCBM was seen most prominently in HER2+ and ER− patients. Conclusion: Receptor subtypes that demonstrated poorer OS tended to demonstrate higher intracranial recurrence. A positive response to radiation was not associated with better OS or lower ICR. Identifying patterns based on receptor subtype may guide clinicians in management and surveillance for BCBM.