Prevalence of estrogen receptor mutations in patients with metastatic breast cancer

The activation of the estrogen receptor (ER) is a feature of most breast cancers in which ER expression is detected. An aromatase inhibitor (AI) for estrogen deprivation therapy is an effective therapy for those tumors and reduces disease illness and death. Outcomes for patients with ER-positive metastatic breast cancer who are treated with AIs vary considerably, with relapse for some patients within months and after many years for others.

Sarat Chandarlapaty, M.D., Ph.D., of Memorial Sloan Kettering Cancer Center, New York, and coauthors conducted a secondary analysis of cell-free DNA from 541 patients enrolled in a clinical trial to determine the prevalence of mutations and whether they were associated with worse outcomes.

The authors report 29 percent of patients had a mutation in the estrogen receptor and mutation was associated with shorter overall survival, according to the report.

"Mutations in the estrogen receptor are common in patients with metastatic breast cancer who were previously treated with an aromatase inhibitor and are associated with worse outcomes," the authors conclude.