Conversion of ER, PR, HER2 and Ki-67 and Prognosis in breast cancer metastases to the brain

Objective: This study aimed to analyze the expression levels of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER-2), and Ki-67 proliferation index in the brain metastatic lesions and primary lesions in Chinese patients with breast cancer brain metastasis (BCBM) and determine the correlation between their changes and patients’ survival. Methods A retrospective analysis was performed on patients with BCBM admitted to the Fifth Medical Center of PLA General Hospital and who underwent craniotomy from January 1998 to December 2021. The clinical characteristic of these patients, the expression levels of ER, PR, HER-2, and Ki-67 in the primary lesions and brain lesions, and the survival were collected. The differences in the expression levels of the ER, PR, and HER-2 between the primary lesions and brain lesions were evaluated, and the association between the differences and survival was analyzed. Results The results of our study showed that the positive rates of ER, PR, and HER-2 in the primary lesions were 35.0% (14/40), 30.0% (12/40), and 60.0% (24/40), respectively, and the positive rates of ER, PR, and HER-2 in the brain metastatic lesions were 35.0% (14/40), 12.5% (5/40), and 55.0% (22/40), respectively. The conversion rate of anyone receptor (ER, PR, or HER2) between the primary lesions and brain metastatic lesions was 45.0% (18/40), of which the ER inconsistency rate was 25.0%, the PR inconsistency rate was 22.5%, and the HER-2 inconsistency rate was 15.0%, and the receptor conversion resulted in a subtype conversion of 27.5% (11/40). The patients with HER-2 expression discordance between the primary lesions and the brain metastatic lesions had significantly longer survival times (58.9 months vs. 26.4 months, P = 0.04) after diagnosis of brain metastases. Conclusion In this study, 45.0% of breast cancer patients developed biomarker-conversion between the primary lesions and brain metastatic lesions, and the differences in the expression levels of the ER, PR, and HER-2, the change in Ki-67 index between the primary lesions and brain lesions had predictive effects on patients’ survival.