Everolimus gains FDA approval for metastatic breast cancer

Postmenopausal women with metastatic, hormone receptor-positive breast cancer may now be treated with everolimus (Afinitor) in combination with exemestane (Aromasin), following FDA’s recent approval of the tablet medicine.

Everolimus is a mammalian target of rapamycin inhibitor (mTOR). When combined with the hormonal therapy exemestane, everolimus increased women’s progression-free survival, or time after treatment began that the cancer did not grow or worsen, versus exemestane alone.

Background of FDA approval

Typically, postmenopausal women with metastatic, hormone receptor-positive breast cancer are treated with aromatase inhibitors, hormonal therapy medicines that stop the estrogen production that drives the growth of hormone-sensitive cancer cells. In time, some cancers build resistance to aromatase inhibitors, and doctors must then switch women to different medicine.

The BOLERO-2 clinical trial, whose findings led to FDA approval of everolimus, tested whether everolimus would make hormonal therapies like exemestane more effective. BOLERO-2 compared the effectiveness of everolimus and exemestane versus exemestane and a placebo (an inactive substance) in 724 women whose hormone receptor-positive, HER2 negative metastatic breast cancer had progressed on letrozole (Femara) or anastrozole (Arimidex).

An early analysis showed that women treated with the combination of everolimus and exemestane had a median 4.1 more months of progression-free survival than the women treated with exemestane alone. A second, central analysis found the everolimus group had a median 6.5 more months of progression-free survival than the placebo group (10.6 versus 4.1 months, respectively). The study was published in the New England Journal of Medicine in February. An analysis of overall survival, or how long women lived after entering the trial, is expected in 2014.

How everolimus works

mTOR is a protein kinase,or type of enzyme, that helps control cell growth. In some cancers, mTOR-activated proteins function abnormally and encourage cancer cells to grow and spread. mTOR also directs nutrients to the cancer cells, helping to sustain them.

Everolimus works to slow or stop mTOR’s function in the growth of cancer cells. Paired with aromatase inhibitors like exemestane, cell growth is stalled by blocking nutrients and directions from mTOR as well as the estrogen that encourages growth.

What this means for you

If you are living with hormone receptor-positive, HER2 negative breast cancer, are postmenopausal and the cancer has progressed despite treatment with either letrozole or anastrozole, starting treatment with everolimus may improve your progression-free survival.

Talk with you doctors about everolimus as a treatment option. Be sure to discuss side effects such as stomatitis, or inflammation of the mouth, infection, rash, diarrhea, decreased appetite and fatigue.