Breast cancer treatments can lead to significant hormonal changes in the body, specifically a dramatic decrease in estrogen or estrogen effectiveness. Practically speaking, women undergoing breast cancer treatment can be launched into menopause nearly overnight. Most of the women will experience severe symptoms of menopause, including hot flashes, GSM, and others. In some cases, the menopause symptoms will abate once treatment has concluded. However, many breast cancer treatment/recurrence protocols can keep women on chemotherapy/chemoprevention for years. Additionally, women with a higher risk of breast cancer, as well as those with a history of breast cancer, have historically been denied access to menopause treatments out of an abundance of caution. Mitigating some of the menopause symptoms of these women is important for quality of life. In this post, I hope to quickly review treatment options and current research regarding the risk of using MHT by these populations.
[[[Quick disclaimer - I am not an oncologist and am not recommending any breast cancer treatment strategy. All breast cancer treatment should be managed by your oncology team. I only add this section to explain how these drugs induce menopause.]]]
Approximately 67%–80% of breast cancers in women are estrogen-sensitive (that is, the cancer cells have receptors for estrogen.) In addition to treatments used for other types of cancers, women with estrogen-sensitive breast cancer receive endocrine therapy. (These medications can be referred to as hormone therapy but should not to be confused with menopause hormone therapy (MHT).) Specifically, some women with estrogen-sensitive breast cancer are given drugs that slow or stop estrogen production or that block the effect of estrogen on tissues, including the cancerous tissues. Estrogen production in women can be stopped/slowed by surgical removal of the ovaries (bilateral oophorectomy), radiation of the ovaries, and/or use of drugs called gonadotropin-releasing hormone (GnRH) agonists that interfere with the brain signals that instruct the ovaries to make estrogen. Examples of GnRH agonists used for breast cancer treatment and prevention include anastrozole, letrozole, goserelin, and exemestane. Selective estrogen receptor modulator (SERM) drugs prevent estrogen from interacting with the estrogen receptors on the cells. Examples of SERMs used for breast cancer treatment and prevention include tamoxifen and toremifene. Anti-estrogen drugs (also referred to as selective estrogen receptor downregulators - SERD) like fulvestrant block the estrogen receptors directly, downregulate expression of estrogen receptors, and destroy existing receptors. Recent research suggests that use of these therapies in combination may be more effective than any one of them alone. Unfortunately, these procedures and drugs also have the net effect of interfering with normal functions of estrogen in the body. They also decrease fertility at least temporarily, if not permanently. They induce menopause and all the symptoms and health risks associated with it. In the case of potentially fatal cancer, however, the downside is worth it.
MHT is the most effective treatment for menopausal symptoms of hot flashes, GSM, and prevention of osteoporosis. However, use of MHT (and any other therapies containing estrogen) is contraindicated in women actively undergoing treatment for breast cancer. In women with a history of breast cancer or genetic risk factors to acquire breast cancer, MHT can be considered for hot flashes after non-hormonal options are tried but failed to reduce symptoms, and symptoms are severe. More and more studies are showing that using MHT is not associated with a higher risk of occurrence or recurrence of breast cancer in women with higher risk, or a history of breast cancer, respectively. For a list of non-hormonal therapies that have been proven effective for hot flashes, look here. Evidence regarding the interaction of those non-hormonal drugs and interventions with drugs used for breast cancer prevention/treatment varies so talk with your gynecologist and oncologists about which ones might work for you. Vaginal estrogen can be considered to treat GSM in women with risk factors or post-cancer, but other options like moisturizers, hyaluronic acid, and DHEA should be tried first. A 2023 review found no increased breast cancer-specific mortality in women who used vaginal estrogen for GSM after breast cancer diagnosis. There is mixed data about whether use of vaginal estrogen increases overall circulating estrogen; therefore, women should work with their gynecologist and oncologist to decide if use of vaginal estrogen is appropriate for them. Women with a history of breast cancer or at higher risk should consider use of non-hormonal options instead of MHT for osteoporosis prevention.
In general, except as described above, women at higher risk for breast cancer or a history of breast cancer can go ahead with the same non-hormonal treatments for all their menopause symptoms as women with no such risk or history. However, women should be aware that some drugs used for menopause symptom relief can interact with cancer hormone therapy drugs so make sure your doctors know all the drugs you are taking. For example, some SSRIs used to treat mood disorders or hot flashes interfere with tamoxifen and make it less effective. There are similar interactions between common drugs like antihistamines, blood pressure medications, and acid reflux drugs with tamoxifen.
In summary, women undergoing breast cancer treatment, at higher risk of breast cancer, or with a history of breast cancer can experience severe menopause symptoms. The relative risk of cancer occurrence/recurrence should be balanced against the risk of using MHT in assessing the impact on a woman's overall quality of life. Shared decision-making between a woman and her doctor should be the standard course of action. Although treatment with MHT is not an option for women actively undergoing breast cancer treatment, there are other proven non-hormonal treatment options for menopausal symptoms. For women post-cancer or with a higher risk of breast cancer, MHT (or vaginal estrogen) can be considered after non-hormonal interventions have been tried. In general, studies are showing that MHT can be used safely in these women, but the risk/benefits must be clearly reviewed using an individualized approach. Where possible, women should work with both their gynecologist and oncologist to determine their relative risks. Women should not believe that they must tolerate their menopause symptoms because of their relationship with breast cancer.
You can get some relief. And you should!