March 01, 2019

A promising treatment for certain breast cancers

Breast cancer comes in several forms, and one of the more aggressive forms — with fewer treatment options — is triple-negative breast cancer. Recently, Mayo Clinic researchers found that the hormone estradiol — available in drug form as Estrace — may have a new use in a certain subset of women with triple-negative breast cancer.

Triple-negative breast cancer accounts for 10 to 20 percent of all breast cancers. It gets the name because it lacks three particular receptors on or inside cancer cells — estrogen receptor alpha, progesterone receptor and human epidermal growth factor receptor 2. Various breast cancer drug treatments are used to target these receptors.

Without those receptors, treatment options for triple-negative breast cancer are mainly limited to surgery, chemotherapy and radiation. These can be effective and curative. However, there are few options for women with residual cancer cells after treatment — meaning recurrence rates for these women are high. In addition, nearly all women with triple-negative cancer that has spread (metastasized) beyond the breast eventually die of the disease.

Mayo Clinic researchers discovered that about 25 percent of those with triple-negative breast cancer have another cell receptor called estrogen receptor beta. Estradiol actually inhibits the growth of triple-negative breast cancer with estrogen receptor beta — including growth and proliferation of metastasized cells. It's an unexpected discovery, since estradiol stimulates cancer growth in breast cancer with estrogen receptor alpha.

So far, these discoveries have been made in the laboratory. A trial of estradiol therapy in women who have metastatic...