After surgery, women diagnosed with hormone-receptor-positive breast cancer usually take hormonal therapy medicine to reduce the risk of the cancer coming back (recurrence). Hormonal therapy medicines work in two ways:
- by lowering the amount of estrogen in the body
- by blocking the action of estrogen on breast cancer cells
There are several types of hormonal therapy medicines. Tamoxifen, a selective estrogen receptor modulator (SERM), is one of the most well-known. Tamoxifen can be used to treat both premenopausal and postmenopausal women. In the early 2000s, the aromatase inhibitors:
- Arimidex (chemical name: anastrozole)
- Aromasin (chemical name: exemestane)
- Femara (chemical name: letrozole)
were shown to be more effective at reducing recurrence risk in postmenopausal women and are now used more often than tamoxifen to treat women who’ve gone through menopause. Aromatase inhibitors aren’t commonly used to reduce recurrence risk in premenopausal women.
Most women take hormonal therapy for 5 to 10 years after breast cancer surgery.
Both tamoxifen and aromatase inhibitors can cause side effects. Tamoxifen may cause hot flashes and increase the risk of blood clots and stroke. Aromatase inhibitors may cause muscle and joint aches and pains. Less common but more severe side effects of aromatase inhibitors are heart problems, osteoporosis, and broken bones. Research has shown that about 25% of women who are prescribed hormonal therapy to reduce the risk of recurrence after surgery either don’t start taking the medicine or stop taking it early, in many cases because of side effects.
A study has found that women who didn’t follow their medicine schedules for chronic conditions such as high blood pressure, diabetes, or thyroid disease before being diagnosed with breast cancer were twice as likely to stop taking hormonal therapy early.
The research was published online on June 9, 2016 by JAMA Oncology. Read the abstract of “Nonadherence to Medications for Chronic Conditions and Nonadherence to Adjuvant Hormonal Therapy in Women With Breast Cancer.”
Dawn Hershman, M.D., M.S., assistant professor of medicine at Columbia University and member of the Breastcancer.org Professional Advisory Board, is one of the authors of the study.
To do the study, the researchers looked at information in MarketScan, a medical and pharmacy insurance claims database. They identified 21,255 women who were 18 or older and had been diagnosed with breast cancer from 2010 to 2012 and also had filled two or more prescriptions for tamoxifen and/or an aromatase inhibitor. The researchers looked to see whether the women had filled prescriptions for six other chronic conditions before being diagnosed with breast cancer:
- high blood pressure
- high cholesterol
- gastroesophageal reflux disease (GERD)
- thyroid disease
About 63% of the women used at least one medicine for one of the chronic conditions listed above.
The researchers also looked to see whether the women filled their hormonal therapy prescriptions on schedule to determine if they took hormonal therapy as prescribed or if they stopped early.
The results showed that of the 21,255 women in the study, 3,314, or 15.6%, stopped taking hormonal therapy early. Several factors were linked to a woman’s stopping hormonal therapy, including:
- being younger than 55 or being age 75 or older
- high out-of-pocket cost for the medicine
- having a number of other health conditions
Women who didn’t take their medicine for one of the six chronic conditions the researchers looked for were twice as likely to stop taking hormonal therapy early compared to women who took medicine for a chronic condition as prescribed.
"Non-adherence to hormone therapy for breast cancer can have significant impact on survival outcomes," the researchers said. "The hope is that by identifying patients at highest risk for non-adherence and having a detailed history of medication use, interventions can be developed and targeted at higher-risk groups."
If you’ve been diagnosed with hormone-receptor-positive breast cancer and will be taking hormonal therapy after surgery and other treatments, it’s very important that you take the medicine for as long as it’s prescribed and at the dose at which it is prescribed. Hormone-receptor-positive breast cancer can come back, and hormonal therapy after surgery reduces that risk -- you must remember that.
Side effects caused by hormonal therapy can be very troublesome for many women. It’s important to talk to your doctor as soon as you start having any side effects, including hot flashes, joint pain, blood clots, trouble sleeping, fatigue, or difficulty concentrating. Don’t wait until the symptoms are intolerable and you have to stop taking the medicine. There are steps you can take to ease these side effects, including switching to a different type of hormonal therapy.
For more information, visit the Breastcancer.org pages on Staying on Track With Treatment. You can read about why it’s so important to stick to your treatment plan, as well as ways to manage side effects after radiation, chemotherapy, and hormonal therapy. If you’re taking hormonal therapy after surgery now, stick with it as prescribed. If you’re thinking of stopping early, talk to your doctor first. Together, you can find a solution that is best for you.