If you're looking for relief from uncomfortable menopause symptoms - such as hot flashes, night sweats, or vaginal dryness - hormone replacement therapy (HRT) may be the answer. HRT medications work by replacing hormones like estrogen and progesterone that naturally go down during and after menopause.

HRT medications are effective for many women. But, like with any medication, risks and side effects are possible. Some studies have linked HRT medications to breast cancer, for example. But data about whether HRT actually raises the risk of breast cancer has been conflicting.

Here, we'll review the research on HRT and breast cancer and factors that may raise the risk of developing cancer.

Does hormone replacement therapy raise the risk for breast cancer?

Research from the Women's Health Initiative (WHI) published in 2002 initially connected HRT to an increased risk of breast cancer. As a result of this research, HRT use declined significantly in all age groups. But, as mentioned, data regarding the risk of breast cancer related to HRT has evolved over time.

Current research on HRT and breast cancer

The WHI study referenced above focused on older women. But many women start experiencing menopause symptoms earlier in life - often in their 40s or 50s. Newer data has helped to clarify the risk of breast cancer with HRT in women younger than 60.

Current research suggests there's a small increase in breast cancer risk when taking combined HRT. This is a form of HRT that contains both an estrogen and a progestin (progesterone). In an updated WHI study, for every 10,000 women that took combined HRT for multiple years, an additional 9 women developed invasive breast cancer. This increase affected specific age groups differently.

There may actually be a lower risk of breast cancer with estrogen-only HRT. In the same study, there were fewer cases of invasive breast cancer in women who took estrogen-only HRT. However, only women who don't have a uterus can receive estrogen-only HRT.

Overall, the risk of breast cancer with HRT appears to be lower among women ages 50 to 59 who have gone through menopause. This was the lowest age range involved in the study; people in their 40s weren't included.

Overall takeaway on HRT and breast cancer risk

HRT is recommended as a safe option for women who are within 10 years of menopause or are under the age of 60 and otherwise healthy. It's typically an option for women in these groups who are experiencing vasomotor symptoms of menopause (and other related symptoms).

Still, it's not recommended to use HRT long-term, meaning usually not more than 5 years.

Factors that increase the risk of breast cancer with hormone replacement therapy

How long you take HRT matters. The longer you take HRT - and are exposed to hormones - the greater the risk of breast cancer.

Another factor is the type of HRT you use. As mentioned, combined HRT has a higher breast cancer risk than estrogen-only HRT.

The form of HRT you use may play a role, too. Systemic forms of HRT, such as estrogen pills and patches, work throughout the whole body. Topical forms of HRT, such as estrogen creams and suppositories, work locally and have more targeted effects. Topical HRT is not thought to raise the risk of breast cancer.

Examples of systemic forms of HRT are:

• Combined estrogen and progestin pills:Activella, Prempro, and Bijuva,

• Estrogen-only pills:Estrace, Menest, and Premarin

• Combined estrogen and progesterone patch:Combipatch

• Estrogen patch:Climara

Examples of topical forms of HRT are:

• Vaginal estrogen ring:Estring

• Vaginal estrogen cream:Premarin

• Vaginal estrogen tablet:Vagifem

Why does HRT increase breast cancer risk?

Some types of breast cancer, such as hormone receptor-positive (HR-positive) breast cancer, use estrogen to grow. While it's not entirely understood how HRT raises the risk of breast cancer, it's thought to be caused by exposure to higher levels of hormones.

Does gender-affirming hormone therapy increase the risk of breast cancer?

Yes, estrogen-based gender-affirming hormone therapy (GAHT) can raise the risk of breast cancer in transgender women and nonbinary people assigned male at birth.

Due to this risk, it's generally recommended that transgender women and nonbinary people assigned male at birth who are 40 years or older receive annual mammograms to screen for breast cancer. This is primarily recommended for those who have received estrogen-based GAHT for more than 5 years.

Does hormone therapy, rather than hormone replacement therapy, increase the risk of breast cancer?

No, hormone therapy doesn't increase the risk of breast cancer. Although hormone therapy sounds very similar to HRT, they're different treatments entirely.

Hormone therapy is used to treat and prevent certain cancers that are sensitive to hormones, such as HR-positive breast cancer. Examples of hormone therapy medications are tamoxifen (Soltamox), anastrozole (Arimidex), and fulvestrant (Faslodex).

Hormone therapy works by blocking or lowering levels of hormones like estrogen. On the other hand, HRT replenishes or replaces hormones like estrogen in the body.

Does hormone replacement therapy increase the risk of ovarian or endometrial cancer?

Ovarian and endometrial (uterine) cancers can also be sensitive to the hormones found in HRT medications. Specific risks vary by cancer type, however.

For instance, a large meta-analysis of women who completed menopause demonstrated a very low risk of developing ovarian cancer following HRT use.

By comparison, a study of women who completed menopause and who took estrogen-only HRTdidshow an increase in endometrial (uterine) cancer. However, the risk of endometrial cancer with estrogen-only HRT can be mitigated by taking a progestin.

Progestins may have a protective effect. This means that taking combined HRT does not cause an increased risk of endometrial cancer. This is because estrogen drives endometrial cancer cell growth, whereas progestin blocks it. This isn't the case for breast cancer cells, and it's also why only women without a uterus can receive estrogen-only HRT.

How to minimize your risk of breast cancer while taking hormone replacement therapy

If you do choose to receive HRT to lessen menopause symptoms, there are a few things you can do to minimize your risk of breast cancer.

First, talk to your healthcare professional about your personal risk of breast cancer (and other hormone-sensitive cancers). If you have a history of breast cancer, it's generally recommended to avoid systemic HRT.

Timing is another factor to think about. It's usually recommended to start HRT within 10 years of going through menopause or before the age of 60. You should also aim to take HRT for the shortest amount of time needed to help ease your symptoms. Overall, research suggests that the benefits of HRT outweigh the risk of breast cancer when taken for less than 4 or 5 years.

Do your best to limit the amount of estrogen you take, too. You can work with your healthcare professional to find the lowest dose of HRT that works to relieve your menopausal symptoms.

You can also consider topical forms of HRT, especially if you're mostly only experiencing vaginal symptoms, such as vaginal dryness. Estrogen rings, suppositories, and vaginal creams usually have a lower dose of estrogen than other forms and don't affect the whole body.