Long-Term Results Confirm Benefits of Ovarian Suppression With Tamoxifen
Eight years of follow-up show that two years of ovarian suppression while a woman diagnosed with early-stage, hormone-receptor-positive breast cancer is taking five years of tamoxifen reduces the risk of recurrence (the cancer coming back) more than tamoxifen alone.
The research was published in the October 2023 issue of the Journal of Clinical Oncology. Read the abstract of “Adding Ovarian Suppression to Tamoxifen for Pre-Menopausal Women With Hormone Receptor-Positive Breast Cancer After Chemotherapy: An 8-Year Follow-up of the ASTRRA Trial.”
Ovarian suppression and hormonal therapy
Ovarian suppression, also called ovarian shutdown, uses medicine to temporarily stop the ovaries from functioning. This is because in pre-menopausal women, most of the estrogen in the body is made by the ovaries.
In 2014, SOFT (Suppression of Ovarian Function Trial) found that five years of tamoxifen plus ovarian suppression offered better disease-free survival than five years of tamoxifen alone.
Disease-free survival is how long a person lives without the cancer coming back.
About the study
This study, called ASTRRA, wanted to see if stopping ovarian function for only two years instead of five would still improve disease-free survival more than tamoxifen alone.
The study included 1,282 pre-menopausal South Korean women ages 45 or younger diagnosed with early-stage, estrogen receptor-positive breast cancer. All the women had surgery to remove the breast cancer and all received chemotherapy, either before surgery or after surgery:
55% of the women had node-positive disease, meaning breast cancer was found in the lymph nodes
13.8% of the cancers also were HER2-positive
57.5% of the women were treated with taxane chemotherapy
All the women were scheduled to take tamoxifen for five years after surgery.
The researchers randomly assigned them to one of two groups:
647 women took five years of tamoxifen
635 women took five years of tamoxifen and also had their ovarian function suppressed for two years; ovarian suppression was done with a monthly injection of Zoladex (chemical name: goserelin)
Results from ASTRRA published in 2019, after five years of follow-up, showed disease-free survival rates were:
91.1% for women who had ovarian suppression with tamoxifen
87.5% for women who took tamoxifen alone
These latest ASTRRA results come after three more years of follow-up. The disease-free survival rates after eight years were:
85.4% for women who had ovarian suppression with tamoxifen
80.2% for women who took tamoxifen alone
This difference was statistically significant, which means it was likely because of the difference in treatment and not just because of chance.
Still, there was no difference in overall survival – how long the women lived whether or not the cancer came back – between the two groups.
“Adding [ovarian suppression] for two years to adjuvant tamoxifen with a longer follow-up resulted in consistent disease-free survival benefits, suggesting that adding [ovarian suppression] to tamoxifen should be considered for patients who remain in a pre-menopausal state or resume ovarian function after chemotherapy,” the researchers wrote.
What this means for you
These long-term results offer reassuring evidence that shutting down the ovaries for two years along with five years of tamoxifen treatment can help reduce the risk of recurrence more than tamoxifen alone.
Still, there are a few things to keep in mind.
When this study started, taking tamoxifen for five years was the standard of care. Today, most women take tamoxifen for 10 years because research found that 10 years is more effective than five. It’s not clear if shutting down the ovaries for two years during 10 years of tamoxifen would offer the same results.
A later analysis of the SOFT study found that ovarian suppression along with tamoxifen caused more side effects and sexual problems than tamoxifen alone. The ASTRRA study didn’t include information on side effects, which is very disappointing.
Research suggests that up to half of women prescribed tamoxifen or another hormonal therapy medicine either don’t take the medicine as prescribed or stop taking it early, in many cases because of troublesome side effects. But it’s important to know that research shows hormone receptor-positive breast cancer may come back 30 or more years after diagnosis.
Hormonal therapy keeps the risk of recurrence as low as it can be. If you’re having troubling side effects from hormonal therapy, such as hot flashes, vaginal dryness, or joint pain, talk to your doctor. In addition to medicines, there are other techniques that can help ease them, including acupuncture, exercise, and mindfulness meditation.
Listen to The Breastcancer.org Podcast episode featuring Dr. Kristin Rojas discussing treatment options for the sexual side effects hormonal therapy may cause.
Better Sexual Health for Women Taking Hormonal Therapy
Jun 7, 2023Updated on February 13, 2024