A new prospective study has reported that determining the receptor status of metastases can be important in planning treatment since receptor status can change during disease progression. The presence of differences in estrogen (ER), progesterone (PR), or human epidermal growth factor receptor 2 (HER2) status between the original tumor and corresponding metastases (including lymph node metastases) is known as "discordance." The study was designed to evaluate the impact of tumor receptor discordance between the original tumor and corresponding metastases on breast cancer patient treatment and survival. Treatment decisions concerning patients with metastatic breast cancer typically are based on the receptor status of the original tumor. Retrospective studies have reported significant levels of discordance between primary tumors and metastases, which can lead to detrimental outcome if treatment is based on the receptor status of the original tumor.

The study included 121 women. In the study, primary tumors and suspected metastases were analyzed for ER, PR and HER2 using similar methodology. The treating oncologist provided a treatment plan both before and after biopsy of suspected metastases in order to assess how the receptor results informed patient management. Study participants were followed for a median of 12 months with respect to disease progression and death.

It was possible to determine the receptor status of the metastases of 80% of the study participants. The use of fine-needle aspiration to obtain tissue samples and bone biopsies both were associated with reduced ability to analyze receptors. Discordance in ER status between the primary tumor and the metastasis was found in 16% of the cases. The discordance rate was 40% for PR and 10% for HER2. The biopsy results led to a change in treatment of 14% of the women. No trends for an association between receptor discordance and either time to relapse or overall survival were observed during follow up. The authors comment that biopsy of metastases is technically feasible in most cases. Treating oncologists modified planned treatment of one in seven patients based on results of the biopsy, and discordance was not then associated with detrimental effects on outcome. The authors conclude that tissue confirmation should be considered in women with breast cancer and suspected metastatic recurrence.