A recent study has good news for breast cancer survivors taking long-term hormone therapy. Among women treated for early stage, hormone-receptor positive breast cancer, aromatase inhibitors reduced the risk of recurrence by more than a third.
The only catch: Women in the study remained on hormone therapy for 10 years, twice the duration commonly prescribed now.
The study, published in July 2016 in the New England Journal of Medicine, followed nearly 2,000 post-menopausal women for six years. It is the first study to document a greater benefit for extending hormone therapy beyond five years.
In many cases, the standard of care is to follow breast cancer treatment with hormonal therapy for at least five years, says Robert Fisher, MD, a Rocky Mountain Cancer Centers oncologist who treats breast cancers. In light of the findings, Fisher says, “it might become more common to give hormonal therapies for up to 10 years, particularly for women at higher risk for recurrence.”
Being overweight, smoking, and consuming more than one alcoholic drink per day increase a woman’s risk of recurrence.
Higher levels of estrogen increase the risk of recurrence in certain types of breast cancer. Before menopause, the ovaries produce most of the estrogen circulating in the body. After menopause, an enzyme called aromatase converts the hormone androgen into estrogen, creating much of the body’s circulating estrogen. Aromatase inhibitors (AIs) block that conversion, which reduces the amount of estrogen in the body.
Aromatase inhibitors can’t prevent the ovaries from producing estrogen, so they aren’t often used in pre-menopausal women.
When widely used first in the 1990s, hormone therapies like tamoxifen produced significant side effects, including fatigue, dizziness, loss of coordination, nausea and vomiting.
Now, tamoxifen has largely been replaced by newer hormone therapies, including aromatase inhibitors, that have fewer side effects. These therapies are taken orally on a daily basis.
If you are a breast cancer survivor and you are considering hormone therapy after treatment, here are some things you should know:
- Hormone therapy is effective only in cancers that are estrogen-receptor positive. Some breast cancers grow with the help of the hormones estrogen and/or progesterone. Those cancer cells have special proteins inside, called hormone receptors. When a tumor has many of those receptors, it is called hormone-receptor positive.
- Hormone therapy for breast cancer survivors is not the same as hormone replacement therapy. Hormone replacement therapies often are used to treat symptoms of menopause by boosting levels of the hormones estrogen and progesterone.
- Aromatase inhibitors generally have fewer severe side effects than those associated with some of the earlier hormone therapies, like tamoxifen. Still, there are potential side effects, including
- Bone loss
- Joint pain and risk of fractures
- Possible heart problems.
Most often, aromatase inhibitors are given to women who have been through menopause. Younger women whose physician recommends therapy with aromatase inhibitors may have more concerns about long-term effects. They should talk with their doctor about the benefits and side effects, Fisher says.
In addition, Hyun Sue Kim, MD, a Rocky Mountain Cancer Centers physician who specializes in treating breast cancers, says she is careful to monitor bone density among patients taking hormone therapy. Frequently, she says, those patients will need supplements to help prevent osteoporosis.