BRCAness of brain lesions reflects a worse outcome for patients with metastatic breast cancer

Purpose Breast cancer often metastasizes to the central nervous system. Although the prognosis of brain metastases from breast cancer has been considered poor, and systemic therapy has not contributed to an improved prognosis, newer agents are expected to be more effective. BRCAness is defined as the status of homologous recombination deficiency (HRD) in tumor tissue, regardless of the presence of pathogenic germline BRCA1/2 variants. A study employing next-generation sequencing analysis showed that HRD was found relatively frequently in brain metastases of breast cancer patients. However, there have been no studies evaluating BRCAness in brain metastases of breast cancer with more efficient, rapid, and cost-effective methods. Methods We retrospectively investigated 17 brain metastases of breast cancer that were surgically resected at our hospital from January 2007 to December 2022. Of these, samples from 15 patients were evaluable for BRCAness by employing multiplex ligation-dependent probe amplification (MLPA) assay. Results Of the 15 patients, five patients (33%) had tumors with BRCAness. Clinicopathological factors of patients with brain metastases with BRCAness were not statistically different from those of patients who possessed tumors without BRCAness. Patients with brain metastases with BRCAness had shorter overall survival compared to those without BRCAness (BRCAness, median 15 months (95% CI 2–30) vs. non-BRCAness, median 28.5 months (95% CI 10–60); P = 0.013). Conclusion In this study, we evaluated BRCAness in brain metastases of breast cancer with the MLPA method, and found that about one-third of patients had BRCAness-positive tumors. The analysis of BRCAness using MLPA has the potential for practical clinical use.