Discordance and Conversion Rates of Progesterone-, Estrogen-, and HER2/neu-Receptor Status in Primary Breast Cancer and Brain Metastasis Mainly Triggered by Hormone Therapy

Background/aim: Knowing the molecular footprint of tumors is a precondition for personalized medicine. For breast cancer, targeted therapies are frequently based on the molecular status of the tissue gained from the primary tumor operation. However, it is unclear whether metastases in different organs maintain the same status.

Patients and methods: We compared the estrogen- (ER), progesterone- (PgR) and HER2/neu receptor status of the primary tumor with brain metastases in a series of 24 consecutive breast cancer patients.

Results: 62.5-75% of patients exhibited a constant receptor status between the primary tumor and the brain metastasis, whereas discordance rates of 25-37.5% were found, depending on the receptor. The rate of ER and PgR expression was each 41.6% in the primary tumors and decreased to 12.5% and 16.6% in the brain metastases. In contrast, the rate for Her2+ tumors increased from 41.6% in primary breast cancer to 65.2% in the respective brain metastases. The Ki-67 proliferation index increased significantly from a mean of 21% at the primary tumor site to 60% in brain metastases (p<0.001). All anti-estrogen treated breast tumors lost the estrogen receptor expression in the brain metastases, whereas no Her2/neu conversions occurred after treatment with trastuzumab.

Conclusion: In summary, receptor conversion is frequent during disease progression. Therefore, the receptor status of the primary tumor is invalid for planning a therapy targeted against brain metastases, especially after hormone-therapy. In these cases, new tissue collection by biopsy or resection is mandatory for the selection of adequate therapeutic targets and accurate decision-making for systemic therapies.