A study looking at how hormonal therapy works in the real word found that women who took hormonal therapy after surgery had a lower risk of#breastcancer in the other breast and this risk got progressively lower the longer a woman took hormonal therapy.
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
Doctors call treatments taken after surgery “adjuvant” treatments.
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 in a general community setting diagnosed with hormone-receptor-positive breast cancer who took hormonal therapy after surgery had a lower risk of breast cancer in the opposite breast -- doctors call this contralateral breast cancer. The study also found that the risk of contralateral disease got progressively lower the longer a woman took hormonal therapy.
The research was published online on Oct. 6, 2016 by JAMA Oncology. Read the abstract of “Association of Adjuvant Tamoxifen and Aromatase Inhibitor Therapy With Contralateral Breast Cancer Risk Among US Women With Breast Cancer in a General Community Setting.”
Many studies have shown that women diagnosed with hormone-receptor-positive breast cancer who take hormonal therapy after surgery have a lower risk of developing breast cancer in the other breast. But as the researchers who did this study point out, the results of a study done in a very controlled clinical environment aren’t always achieved in the real world. For example, in clinical studies, women have to document that they took the complete course of hormonal therapy. In the real world, we know that many women stop taking hormonal therapy early or may stop taking the medicine for a long period of time and then start taking it again.
Hormonal Therapy After Surgery Reduces Risk of Breast Cancer in Opposite Breast in Real-World Setting
So the researchers wanted to measure the benefits of hormonal therapy in a real-world setting.
To do the study, the researchers looked at the records of 7,541 women diagnosed with breast cancer between 1990 and 2008. The women lived in Colorado or Oregon.
The women ranged in age from about 25 to about 85; about 93% of the women were white. The researchers had about 6 years of follow-up information on the women.
About half the women in the study took tamoxifen:
- 52% of the women (3,900 women) took tamoxifen -- half the women took the medicine for fewer than 3.3 years and half the women took the medicine for longer than 3.3 years
- About 25% of the women (1,929 women) took an aromatase inhibitor:
- 963 women took both tamoxifen and an aromatase inhibitor -- half the women took hormonal therapy for fewer than 2.2 years and half the women took hormonal therapy for longer than 2.2 years
- 966 women took only an aromatase inhibitor -- half the women took the medicine for fewer than 2.9 years and half the women took the medicine for longer than 2.9 years\