New biomarker predicts effectiveness of breast cancer drugs

Researchers suggested the findings could help physicians more accurately predict which tumors will respond to anti-estrogen therapy and improve long-term survival for breast cancer patients.

The UC researchers found that when a pathway controlling cell growth known as the retinoblastoma (RB) tumor suppressor is disrupted or “shut off,” the tumor resists anti-estrogen drugs and the cancer continues to grow in spite of the therapy.

“Since evidence shows anti-estrogen drugs will fail in a many patients with estrogen-receptor-positive breast cancer,” said Erik Knudsen of the University of Cincinnati.

“Our research suggests that physicians should examine both estrogen receptor status and RB tumor suppressor status during the initial diagnosis, in order to prescribe the most effective therapy for that specific patient’s cancer.”

In the study, the team disrupted the RB suppression pathway in breast cancer cells and analyzed the impact on tumor growth using animal models. The researchers then compared their results with a large patient record database to determine if the same phenomenon was occurring in patients with estrogen receptor-positive breast cancer. Studies supported their hypothesis that RB may be a critical determinant of whether a tumor will respond to anti-estrogen therapy.