In a study, women previously treated for breast cancer who took hormone replacement therapy (HRT) to ease menopausal symptoms had a much higher risk of the original breast cancer coming back than survivors who didn't take HRT. Other research also has shown that HRT can increase a woman's risk of developing breast cancer for the first time.
After 5 years in the study, the women who took HRT were about 3 times more likely to have the original breast cancer come back than the women who didn't take HRT (22% of the women who took HRT had the breast cancer come back after 5 years, compared to only 8% of those who didn't take HRT). The researchers stopped this study when they saw that the difference between the 2 groups was so great.
This study didn't look at whether different types of HRT might have different effects on the risk of the cancer coming back. Other research has shown that using estrogen-only HRT instead of combination HRT (contains both estrogen and progesterone) may be less likely to increase breast cancer risk, especially if estrogen-only HRT is taken for fewer than 3 years.
If you've been treated for breast cancer and are now struggling with menopausal symptoms, you and your doctor may be considering HRT. This study suggests that taking HRT could increase your risk of the cancer coming back. You might want to talk to your doctor about ways to manage your menopausal symptoms that don't involve HRT. If you do decide to use HRT, ask your doctor about estrogen-only HRT. And try to take HRT for the shortest time possible.
Learn more about more about menopause and ways to manage symptoms in the breastcancer.org Managing Menopausal Symptoms section.