Breast Radiotherapy: A Potential Risk Factor for Resistant Clone Development in Patients with Brain Metastasis

Objective:The human brain is a frequent site of breast cancer metastasis.The various therapeutic approaches for treating brain metastases include surgical intervention, stereotactic radiosurgery (SRS), and whole-brain radiotherapy (WBRT).However, the literature on the association between prior breast RT and the effectiveness of intracranial RT subsequent to treatment is scarce.The present study, therefore, aimed to understand the association between previous breast RT and intracranial progression-free survival (iPFS). Material and Methods:In the present study, the relationship of epidemiological, pathological, and clinical features, especially previous breast RT, with iPFS was explored in the patients diagnosed with human epidermal growth factor receptor 2-positive breast cancer along with brain metastasis.These patients did not undergo surgery for brain metastasis and received WBRT/SRS instead.Results: Fifty-one patients were included in the present study.The median age of these patients was 46 years.Among the included patients, 20 patients had previously undergone whole breast or chest wall RT.In 19 patients, SRS was utilized rather than WBRT.The iPFS was significantly shorter in patients who had previously received RT for the primary lesion compared to those who had not received RT (mPFS: 7.96 vs. 14.56 months, p=0.002, hazard ratio: 3.06, confidence interval: 1.52-6.12).No relationships of iPFS with the treatments used prior to RT, type of RT, sites of metastasis during RT, systemic therapy administered after RT, and status of de novo metastatic/recurrent disease were noted. Conclusion:Patients who had undergone previous RT to the locoregional region exhibited significantly poorer iPFS following the RT performed for brain metastasis.