Breast cancer is the most prevelent cancer in women in the United States, and experts estimate that close to 300,000 cases will be diagnosed in 2022. There are many types of breast cancer, some of which are sensitive to the hormones that naturally circulate through the body. Upon diagnosis, doctors can identify if cancer is sensitive to estrogen or progesterone, sex hormones that fuel cancer growth. This knowledge helps doctors and patients determine an appropriate course of treatment.
One subtype of breast cancer is estrogen receptor-positive (ER+), indicating that the cancer cells express a protein that binds estrogen. Hormone therapies that reduce circulating estrogen levels or block estrogen from binding its receptor on the cancer cells are often used to treat patients with ER+ breast cancer.
Aromatase inhibitors inhibit the natural production of estrogen by blocking aromatase, an enzyme required for generating the hormone. These drugs are typically used to treat postmenopausal women. Tamoxifen is more commonly used in premenopausal women. Tamoxifen binds to the estrogen receptors on the cancer cell, preventing estrogen from engaging with its receptor. Another therapy used for ER+ breast cancer is ovarian suppression, surgical intervention, or drug treatment that stops the production of hormones in the ovaries. Because cancer cells need estrogen to grow, both of these therapies can effectively slow tumor progression.
A study published in The Lancet Oncology investigated whether premenopausal women could benefit from aromatase inhibitors if given in combination with ovarian suppression. The researchers identified four Phase three randomized clinical trials (TEXT- NCT00066703, SOFT- NCT00066690, HOBE- NCT00412022, ABCSG XII- NCT00295646), including ER+ breast cancer patients who received either an aromatase inhibitor and ovarian suppression or tamoxifen and ovarian suppression. Using data from these four studies, the investigators compared outcomes in premenopausal women treated with ovarian suppression and aromatase inhibitors to women treated with ovarian suppression and tamoxifen. The meta-analysis included over 7,000 patients, and the median follow-up time was eight years.
Recurrence rates in women treated with an aromatase inhibitor were about 3% less than those treated with tamoxifen. Distant metastases were also reduced in those treated with aromatase inhibitors. Despite the differences in recurrence and metastasis, there were no statistically significant differences in mortality between the treatments. The authors suggest that a longer follow-up time may be needed to better understand the impact of these therapies on mortality.
Sources: CA, Lancet Oncol