Hormone replacement therapy (HRT) and breast cancer
Some women are wary of taking hormone replacement therapy (HRT) because of fears about a link to breast cancer. Here we discuss the risk factors for breast cancer and the scientific data on the relationship between breast cancer and HRT.
About 1 in 8 women will develop breast cancer in their lifetime. This is the case both before and after menopause, and whether or not they take HRT. Because of screening, early diagnosis and improved treatment, breast cancer survival has improved significantly over the last few decades and the majority of women survive their diagnosis and recover with treatment.
What increases the risk of breast cancer?
Risk factors for breast cancer include increasing age, a previous history of breast cancer (if someone has had cancer in one breast, they’re more likely to develop cancer in the other breast), a family history of breast cancer, gene mutations such as BRCA1 and BRCA2 and younger age at first period and older age at menopause. Certain lifestyle factors are also associated with an increased risk such as lack of exercise, smoking, alcohol, and being overweight over the age of 50.
Does HRT increase the risk of breast cancer?
Over the years, HRT has unfairly attracted a lot of negative media attention, however research shows that it is safe for the majority of women and has many benefits which are often not mentioned in discussions about possible risks.
The risk of breast cancer from HRT depends on the type of HRT, the type of progestogen used in HRT, age of the woman at first use and how long it’s used for.
Combined HRT, where estrogen and progestogen (a synthetic version of the hormone progesterone) are taken together (used in women who have a uterus or womb), may be associated with a small increased risk of breast cancer when used for more than 5 years, and with some older progestogens. However, this risk is low and needs to be seen in the context of the breast cancer risks associated with other conditions. For example, the risk of breast cancer associated with being overweight over the age of 50 is greater than that with combined HRT and is similar to, or less than that associated with drinking 2 or more units of alcohol per day. Approximately 2% of breast cancer cases in the UK are thought to be related to the use of HRT, compared to about 8% of cases related to alcohol use.
On the other hand, estrogen-only HRT [used in women who’ve had their uterus removed (hysterectomy)] and vaginal estrogen do not carry an increased risk of breast cancer.
Women who start HRT at a younger age because of early or premature menopause do not have an increased HRT-related breast cancer risk until they reach the natural age of menopause, which is around 51 in the UK.
Can I have HRT if I have a family history of breast cancer?
Most breast cancers actually occur in women who have no family history of breast cancer.
If you do have close relatives who have had breast cancer, you may have a higher risk of developing breast cancer, but this is usually unrelated to the use of HRT and available evidence suggests that using HRT does not appear to have an additive effect, meaning it does not appear to increase this risk further.
Breast cancer is common, so it is possible for it to occur in more than one family member just by chance.
Is HRT safe in people who have the BRCA 1 and BRCA 2 genes?
If you have a significant family history with more than one first degree relative (mother or sister) who have breast or ovarian cancer, you may need genetic testing.
Mutations in genes known as BRCA1 and BRCA2 can increase your risk of developing both breast and ovarian cancer (a mutation is a permanent change in the structure of a genes). Some women choose to have their ovaries surgically removed to reduce these risks, and some women will also undergo preventative mastectomy (breast removal) as well.
Removing the ovaries triggers menopause, and in younger women in particular, apart from causing menopausal symptoms, this may have significant health consequences particularly on the bones, heart and the brain, so taking HRT is usually recommended.
Many women who have their ovaries removed will also have their uterus removed at the same time, so these women will only need estrogen as their HRT which is not associated with an increased risk of breast cancer.
What about HRT for women with a history of breast cancer
Systemic HRT (pills, patches, gels, implants and sprays) generally isn’t recommended, especially if the breast cancer was hormone sensitive, because of the potential increased risk of recurrence. Breast cancers are said to be hormone sensitive when the cancer cells contain estrogen receptors (ER) or progesterone receptors (PR). Estrogen and progesterone hormones attach to these receptors and help the cancer cells to grow. Most ER-positive breast cancers are also PR positive. Breast cancers that lack ERs are called ER negative, and if they lack both ER and PR they may be called HR negative. Approximately 67%–80% of breast cancers in women are ER positive.
Although HRT is usually not recommended following breast cancer treatment, for the reasons stated above, menopausal symptoms in some women can be so troublesome and their quality of life so impaired, HRT may be offered in exceptional cases following discussion of the potential risks and benefits.
In addition, younger women with early or premature menopause triggered by breast cancer treatment are also at a significantly higher risk of cardiovascular disease and osteoporosis, so HRT may be considered in individual cases.
It is important that women are given all the information they need to make informed choices about the risks and benefits of HRT. And any decision to prescribe HRT should be taken in conjunction with the patient’s specialist breast cancer team.
It is also important to note that low dose vaginal estrogen can be safely used in most women with a history of hormone receptor-negative breast cancer, and in some women with hormone receptor positive cancer. This should only be done under specialist supervision.
How can you reduce your risk of getting breast cancer?
The risk of breast cancer can be reduced by maintaining a healthy weight, having a healthy diet, exercising regularly, not smoking and limiting alcohol intake – people who drink even small amounts of alcohol on a regular basis have a greater risk of breast cancer than people who do not drink alcohol at all.
It’s important for women to be aware of how their breasts normally look and feel, and to report any changes to their doctor right away. Having regular mammograms is also important.
