On July 20, 2012, Afinitor (chemical name: everolimus) was approved by the U.S. Food and Drug Administration (FDA) to be used in combination with Aromasin (chemical name: exemestane) to treat advanced-stage, hormone-receptor-positive, HER2-negative breast cancer in postmenopausal women that has already been treated with Femara (chemical name: letrozole) or Arimidex (chemical name: anastrozole).
Locally advanced breast cancer is cancer that has spread beyond the breast to the chest wall below the breast or the skin on top of the breast. Metastatic breast cancer is advanced-stage cancer that has spread to parts of the body away from the breast, such as the bones or liver.
Aromasin, Femara, and Arimidex are all aromatase inhibitors, a type of hormonal therapy. Aromatase inhibitors stop the production of estrogen in postmenopausal women. Aromatase inhibitors work by blocking the enzyme aromatase, which turns androgen hormones into small amounts of estrogen in the body. This means that less estrogen is available to stimulate the growth of hormone-receptor-positive breast cancer cells.
A targeted therapy medicine, Afinitor is an mTOR (mammalian target of rapamycin) inhibitor. mTOR is a kinase, a type of protein in the body. Kinases help all cells -- both healthy and cancer cells -- get the energy they need. When kinases don’t act normally or are overactive, they help certain breast cancers grow. mTOR inhibitors work by interfering with the mTOR kinase. Afinitor is a pill taken by mouth.
The FDA based its approval of Afinitor on results from the BOLERO-2 study. That study showed that postmenopausal women diagnosed with advanced-stage, hormone-receptor-positive, HER2-negative breast cancer who got Afinitor and Aromasin lived 4.6 months longer without the cancer growing (progression-free survival) compared to women who got Aromasin and a placebo (a sugar pill that looked like Afinitor). All the women had already been treated with either Femara or Arimidex, but the cancer had stopped responding to that treatment.
The most common side effects of Afinitor are mouth sores, rash, infections, fatigue, diarrhea, and a lack of appetite. Lung infections, trouble breathing, and kidney failure can be serious side effects of Afinitor. Women age 65 and older had a higher rate of serious side effects than younger women when taking Afinitor.
If you’re a postmenopausal woman being treated for advanced-stage, hormone-receptor-positive breast cancer, you and your doctor may be considering a number of treatment options, especially if the cancer has stopped responding to standard treatments such as an aromatase inhibitor. You may want to ask your doctor about the FDA’s approval of Afinitor and whether Afinitor should be part of your treatment plan.