While the chemotherapy drug tamoxifen has long been associated with a risk of fatal cardiovascular events, a recent study shows that a newer class of breast cancer drugs has the same level of risk. However, aromatase inhibitors also have an increased risk of less severe cardiovascular complications compared to tamoxifen.
The three aromatase inhibitors on the market are anastrazole (Armidex), exemestane (Aromasin) and letrozole (Femara).
In older breast cancer survivors, cardiovascular disease is a leading cause of death. Prior research had already associated tamoxifen with an increased risk of fatal cardiovascular events, such as heart attack and stroke. But the new study is one of the first to demonstrate that aromatase inhibitors, though newer, have a similar risk profile in this area.
And it also found that women with breast cancer who had taken either aromatase inhibitors alone or after tamoxifen treatment had between a 26% and 29% higher risk of less serious cardiovascular events, such as irregular heart beat and swelling and irritation of a membrane surrounding the heart, compared to women who had only taken tamoxifen. The new research was published in JAMA Oncology.
“Our study is a comprehensive assessment of the impact aromatase inhibitors have on cardiovascular risk and provides reassurance that the hormone therapy to reduce breast cancer recurrence does not increase risk of the most fatal cardiovascular events,” Reina Haque, PhD, MPH, research scientist, Kaiser Permanente Southern California Department of Research & Evaluation, said in a statement.
“A particular strength of our study is that we accounted for women’s other potential cardiovascular risk factors as well as medication used to treat high blood pressure and high cholesterol,” she added.
Estrogen and progesterone are hormones produced by women that can promote the growth of some breast cancers. Aromatase inhibitors work by blocking the activity of an enzyme called aromatase, which the body uses to make estrogen in the ovaries and in other tissues. Tamoxifen binds to estrogen receptors and interferes with estrogen’s ability to stimulate the growth of breast cancer cells.
Clinical guidelines recommend tamoxifen for five years for women with breast cancer to cut the trisk of the cancer returning. Some postmenopausal women choose to only take aromatase inhibitors, while others choose to take tamoxifen for one to five years, followed by using aromatase inhibitors.