In many women with recurrent breast cancer, the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status of their tumors changes between treatment for the primary tumor and relapse, a large retrospective study has found. The findings, published June 18 in the Journal of Clinical Oncology, support previous studies that have also detected changes in these biomarkers during cancer progression.

These three biomarkers help doctors choose the best treatments for individual women. Therefore, tumors that recur in the breast or appear elsewhere in the body should be biopsied “as a routine procedure” because the results may influence treatment decisions, recommended the authors led by Dr. Linda Lindström of Cancer Center Karolinska in Sweden.

Dr. Lindström and her colleagues used information from pathology reports for 1,010 women treated at three hospitals in Stockholm, all of whom had biopsies taken from their primary and recurrent breast tumors.

Primary and recurrent tumors from 459 women were tested for ER expression. In almost 33 percent of those women, the ER status of the tumor changed (ER expression started or stopped) between treatment and relapse. More than 40 percent of the 430 women whose tumors were tested for PR expression had a change in PR status between treatment and relapse. And almost 15 percent of the 104 women whose primary and recurrent tumors were tested for HER2 expression had a change in HER2 status between treatment and relapse.

In women whose cancers relapsed multiple times, similar proportions of changes to biomarkers were observed.

Prior treatment appeared to influence some biomarker changes. For example, women previously treated with hormone therapy were more likely than women who did not receive hormone therapy to have changes in tumor ER expression. The authors also found that women with ER-positive primary tumors that lost ER expression at relapse had a higher risk of death than women with stable tumor ER expression.

Treatment for metastatic breast cancer is often based on primary tumor characteristics. For some patients, biopsy results will show that the tumor has changed. Therefore, “verifications will be important and may change management options,” concluded the authors.