After surgery, women diagnosed with early-stage, hormone-receptor-positive breast cancer usually take hormonal therapy medicine to reduce the risk of the cancer coming back (recurrence). Hormonal therapy given after surgery is called adjuvant hormonal therapy.
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. The aromatase inhibitors:
- Arimidex (chemical name: anastrozole)
- Aromasin (chemical name: exemestane)
- Femara (chemical name: letrozole)
have been 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.
Right now, aromatase inhibitors aren’t commonly used to reduce recurrence risk in premenopausal women. But because they’re so much more effective in postmenopausal women, researchers wondered if there were a way to successfully treat premenopausal women diagnosed with hormone-receptor-positive, early-stage breast cancer with an aromatase inhibitor. Researchers also wondered if ovarian suppression would make tamoxifen more effective in reducing recurrence risk.
The results of the SOFT (Suppression of Ovarian Function Trial) study suggest that tamoxifen plus ovarian suppression reduces recurrence risk a little more than tamoxifen alone for premenopausal women diagnosed with early-stage, hormone-receptor-positive breast cancer. But Aromasin plus ovarian suppression reduces the risk of recurrence even more for this group of women.
The study was published online on Dec. 11, 2014 by the New England Journal of Medicine and presented at the 2014 San Antonio Breast Cancer Symposium on the same day. Read the abstract of “Adjuvant Ovarian Suppression in Premenopausal Breast Cancer.”
Watch Marisa Weiss, M.D.'s interview with Prudence Francis, M.D., lead author of the SOFT study.
In the SOFT study, 3,066 premenopausal women diagnosed with hormone-receptor-positive, early-stage breast cancer were randomly assigned to get one of three treatments:
- tamoxifen for 5 years
- tamoxifen for 5 years plus ovarian suppression with either 5 years of Trelstar (chemical name: triptorelin), surgical removal of the ovaries, or ovarian radiation
- Aromasin for 5 years plus ovarian suppression with either 5 years of Trelstar, surgical removal of the ovaries, or ovarian radiation
About 47% of the women in the study hadn’t received chemotherapy before, and about 53% had received chemotherapy but were still premenopausal. In other words, their ovaries were still functioning after chemotherapy.
After about 5.5 years of follow-up, the 5-year disease-free survival rates were:
- 86.6% for all women treated with tamoxifen and ovarian suppression
- 84.7% for all women treated with tamoxifen alone
This slight difference wasn’t statistically significant, which means that it could have been due to chance and not because of the difference in treatment.
Disease-free survival means the women were alive without the cancer coming back.
When the researchers looked at the women who had received chemotherapy before, they found that Aromasin plus ovarian suppression reduced the risk of recurrence more than tamoxifen plus ovarian suppression or tamoxifen alone. Five years after treatment, the numbers of women who had not had a recurrence were:
- 78.0% of the women treated with tamoxifen
- 82.5% of the women treated with tamoxifen plus ovarian suppression
- 85.7% of the women treated with Aromasin plus ovarian suppression
“We found that with the addition of ovarian suppression to tamoxifen, four or five fewer patients out of 100 experienced a breast cancer recurrence within 5 years in the group of patients who remained premenopausal after chemotherapy,” said Prudence Francis, M.D., head of breast medical oncology at the Peter MacCallum Cancer Centre in Melbourne, Australia and lead author of the study. “However, we found an even greater reduction in recurrence in this same patient group with the use of ovarian suppression plus the aromatase inhibitor exemestane, which resulted in seven or eight fewer patients out of 100 experiencing a breast cancer recurrence within 5 years.”
Women younger than 35 who had been treated with chemotherapy seemed to get the most benefits from Aromasin plus ovarian suppression:
- one in three women of this age treated with tamoxifen alone had a recurrence within 5 years
- one in six women of this age treated with Aromasin plus ovarian suppression had a recurrence within 5 years
“I believe that these results will result in changes in clinical practice,” Dr. Francis continued. “For women who have not reached menopause and have hormone-receptor-positive breast cancer that carries sufficient risk of recurrence that they receive chemotherapy, physicians are likely to discuss the option of treatment with ovarian suppression plus an aromatase inhibitor.”
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, as well as hot flashes. Less common but more severe side effects of aromatase inhibitors are heart problems, osteoporosis, and broken bones.
About 30% of the women in all three treatment groups reported severe side effects. Women who were taking Aromasin were slightly more likely to withdraw from the studies because of side effects. The researchers are continuing to follow the women in the SOFT study and plan to offer future updates on side effects and the quality of life of the women in the study.
If you’re a premenopausal woman diagnosed with early-stage, hormone-receptor-positive breast cancer that’s been treated with chemotherapy and are considering which hormonal therapy medicine to take, you may want to talk to your doctor about this study.
If you’re willing to take medicine to suppress your ovaries, you may be able to take Aromasin instead of tamoxifen for your hormonal therapy treatment.
While the side effects of hormonal therapy can be very severe for some women, they’re overshadowed by the reality that hormone-receptor-positive breast cancer can come back. Hormonal therapy after surgery reduces that risk. If side effects are a major problem for you, talk to your doctor about ways to manage them. Studies have shown that exercise and acupuncture may reduce hormonal therapy side effects. Visit the Breastcancer.org Staying on Track With Treatment pages to learn more about how to ease side effects.
And stay tuned to Breastcancer.org Research News for the latest updates on the SOFT study.
Editor's note: The "Adjuvant Ovarian Suppression in Premenopausal Breast Cancer” study was published online by the New England Journal of Medicine on Jan. 29, 2015. Click on the link to read the abstract.
Read more news from the 2014 San Antonio Breast Cancer Symposium:
- Low-Fat Diet and Weight Loss Improves Survival in Some Women
- Male Breast Cancer Is Different in Terms of Biology and Outcomes
- Abraxane Offers More Benefits Than Taxol When Given Before Surgery to Treat Early-Stage Disease
- Tamoxifen’s Benefits Long-Lasting for High-Risk Women
- Faslodex Offers Better Survival Than Arimidex as First Treatment for Women With Advanced-Stage Disease
- Oncotype DX DCIS Test Helps Predict Risk of Recurrence
- High Levels of Immune Cells in HER2-Positive Cancers May Mean Tumors Need Only Chemotherapy