Comparative study of Hormonal Receptor Status Discrepancy - Brain Breast Cancer Metastasectomy vs Other Localities.

Abstract Purpose: Hormonal receptor (HR) status is one of the key factors when determining the treatment of breast cancer. Even though HR conversion is one of the most researched topics recently, most of the previous studies include only the results of biopsies instead of samples obtained by metastasectomy. Aim: The aim of this study is to compare the occurrence of HR status conversion in brain breast cancer metastatic tissue to other localities. Methods: A total of 50 patients after breast cancer metastasectomy of brain, lung or liver were included in the study. The clinical characteristics were recorded. Results: HR conversion was observed in a total of 30 cases (60.0%), while HER2 (human epidermal growth factor receptor 2) discrepancy occurred only in one case (2.0%). Endocrine therapy significantly contributed to the decrease progesterone and estrogen receptor expression in metastatic tissue compared to the primary tumor (p = 0.009, p = 0.023; respectively). Triple negativity was more common in the brain metastases (p = 0.039). Liver metastases occurred in significantly younger patients (p = 0.034), however brain metastases had the poorest OS (p = 0.007). Conclusion: HR conversion occurs in more than 50% of cases of breast cancer metastatic disease, while HER2 discrepancy is rare. Hormonal therapy significantly contributes to the decrease of HR positivity in metastases. Triple negativity is more common in the brain metastases than in other localities. Brain metastases of breast cancer are associated with the poorest prognosis.