HRT & Breast Cancer: Facts & Updated Recommendations

Hormone replacement therapy (HRT) and its relationship to breast cancer has been a controversial topic for many years. A common treatment for menopausal women, HRT was discontinued by many after the publication of a prominent government-backed 2002 study linking HRT to breast cancer (1), but recent studies have revealed a more subtle relationship, leading to new therapy guidelines based on breast cancer risk levels.

What Is Hormone Replacement Therapy (HRT)?

Hormone replacement therapy (HRT) is also referred to as menopausal hormone therapy (MHT) or postmenopausal hormone therapy (PMHT, PHT). It is sometimes misleadingly referred to as estrogen replacement therapy, although therapy regimens can use a combination of the estrogen, progesterone and testosterone hormones. HRT is used to treat female menopause symptoms like hot flashes, sleep disturbances, palpitations, anxiety, vaginal dryness and atrophy, bone loss, skin aging, decreased muscle mass, and sexual dysfunction.

Is HRT Linked To Breast Cancer?

In 1993, the Women’s Health Initiative (WHI) was created by the National Institute of Health. It was one of the largest studies of its kind, following over 160,000 post-menopausal women over a 15-year period, studying cancer, cardiovascular disease and osteoporosis. The study found a breast cancer risk increase to 24% for women who took estrogen-progesterone therapies (2), which is an increase of 12% over the baseline risk of 12.5%. This is equivalent to 9 additional breast cancers for every 10,000 women. The study also showed a decreased risk of 20% for women who took estrogen-only therapies (2). The results garnered intense media attention, a drastic reduction in HRT prescriptions, and a decrease in breast cancer diagnoses in the following year, a decrease which, in a 2007 New England Journal of Medicine paper, was attributed to the drop in HRT use (3).

However, since 2002, additional and longer follow-up studies have continued to explore how HRT and breast cancer are related. A 2018 study published in the Lancet found that all types of hormone replacement therapies except vaginal therapies increased breast cancer risk, with estrogen-progesterone combinations increasing risk the most (4). In contrast, a 2019 study presented at the San Antonio Breast Cancer Symposium re-confirmed the WHI’s finding that estrogen-only HRT therapies reduce breast cancer risk (5). So the issue is still unresolved and studies are ongoing.

Based on these and other recent studies examining hormone type, patient age and length of therapy use, the medical community has re-evaluated guidelines on HRT use on a more individual basis depending on breast cancer risk level. Type and timing of HRT are important considerations now and should be discussed with your physician.

HRT for the Average Woman

Generally, when menopause symptoms are disruptive, that is when I recommend a hormone replacement therapy to my patients. And even then, I recommend treating targeted symptoms, for instance a vaginal HRT for vaginal dryness. For women who have had a hysterectomy, I recommend the lowest dose estrogen-only HRT for the lowest length of time, under 5 years. For women with an intact uterus, I would recommend the estrogen-progesterone HRT combination, also at the lowest dose and time length possible.

HRT for BRCA-Positive & Other High-Risk Women

Women who have a high risk of breast cancer, for instance those who have a BRCA1 or BRCA2 mutation or those with a strong family history, should avoid hormone replacement therapy if possible. Before trying HRT, I try treating menopause symptoms with non-hormonal methods first. For hot flashes, a selective serotonin reuptake inhibitor (SSRI) could be prescribed, and for vaginal dryness, an over-the-counter lubricant could relieve symptoms.

I do not recommend vaginal laser therapies, which are not FDA-approved to treat menopause-related vaginal issues (6), nor are they approved by the American College of Obstetricians and Gynecologists (7). You should also be cautious with natural supplements. They have variable ingredients and strength, and lack safety data. Some have negative side effects on blood clotting or may interfere with medications you are taking.

If all non-HRT therapies have been exhausted, HRT may still be utilized. Current recommended doses of hormones are half as much as was used in the 2002 WHI study and so the effect on breast cancer risk levels may be less. As with a normal risk woman, the smallest amount of medication for the smallest amount of time is best. Many patients will take an HRT for 6-18 months, and are successfully able to taper off after that.

HRT for Breast Cancer Survivors

Breast cancer survivors are a special category. Not only can they begin menopause early as a result of breast cancer treatment, they fall into an even higher risk category than those with BRCA mutations or a family history. Taking HRT after breast cancer is not recommended. For these women, it’s best to treat menopause symptoms with non-HRT medications and therapies.

More and more newly diagnosed breast cancer patients are young and premenopausal, and have significant survivorship issues that need to be addressed. There can be a profound effect of estrogen deficiency in these patients that negatively affect bone health and genital and urinary organ conditions, which often need to be addressed.

Vaginal estrogen products, approved by the American College of Obstetricians and Gynecologists (ACOG) in 2017, can be used. According to their statement, which was reaffirmed in 2020, vaginal estrogen products have shown no increased risk of breast cancer recurrence among women currently undergoing treatment or among those with a history of breast cancer who use vaginal estrogen (8). Many studies have been done demonstrating that serum levels of estrogen in the blood are very low to non-existent.

The Bottom Line

There is still controversy with hormone replacement therapy, so it’s good to be cautious, however new data has come out since 2002 and there are new products at lower doses that can be used safely. If menopause symptoms are disrupting your life, many options are available, no matter your risk level. Don’t be afraid to talk to you doctor to create a therapy plan that works for you.