What Medications are Used to Reduce Breast Cancer Risk?

If you’ve been identified as having a high risk of developing breast cancer, then it’s time to discuss your individualized approach to breast cancer risk reduction. In addition to lifestyle modifications, including nutrition and physical activity, a woman can also take medications to reduce her risk for breast cancer. Some women can reduce their risk for breast cancer by up to 50% when taking one of these medications daily for 5 years. Each medication option has its own risks and benefits, so it is important that you partner with your treating provider to discuss if medication is a good option for you.

There are two main types of medications used to lower breast cancer risk: SERMs and Aromatase Inhibitors. 

SERMs: Selective Estrogen Receptor Modulators 

These medications block estrogen in some tissues in the body but act like estrogen in other tissues in the body. Estrogen will cause breast cancer cells to grow if it is a hormone responsive to breast cancer. Since SERMs block estrogen in breast cells, they can lower breast cancer risk.

The medications in the SERM category are the only ones FDA approved in the United States to reduce risk for breast cancer. 

Tamoxofin

How does it work? 

Tamoxifen blocks estrogen in breast cells. When taking to lower the risk of breast cancer, it should be taken once per day for 5 years.

Who should take it? 

It is approved to take in women who are both pre-menopausal and post-menopausal. It is the only option in women who are pre-menopausal to help reduce the risk for breast cancer. 

Common side effects: 

• hot flashes 
• night sweats 
• vaginal dryness or irritation 
• vaginal discharge 
• Possible weight gain 

Risks: 

• Blood clots
• Possible risk of stroke or heart attack given the risk of blood clots, but this is not entirely clear
• Increased risk of cancer of the uterus

Raloxifene

How does it work? 

Raloxifene blocks estrogen in breast cells. When taking to lower the risk of breast cancer, it should be taken once per day for 5 years.

It does not exert estrogen-like effects on the uterus, so it does not carry the risk of uterine cancer that tamoxifen does. There is less risk of breast cancer compared to tamoxifen, but the risk reduction is still close to 40%. 

Who should take it? 

Only post-menopausal women

Common side effects: 

• Hot flashes 
• Vaginal dryness or irritation 
• Joint and muscle pain
• Weight gain

Risks: 

• Blood clots 
• Stroke

Aromatase Inhibitors - AIs

Common names for aromatase inhibitors: anastrozole (Arimidex), letrozole (Femara), exemestane (Aromasin) 

How do they work? 

These medications block aromatase (an enzyme in fat tissue that takes other hormones and turns them into estrogen). By blocking this enzyme, it lowers estrogen levels. Estrogen can cause breast cancer cells to grow if they have receptors on them responsive to estrogen.

When taking to lower the risk of breast cancer, it should be taken once per day for 5 years. 

Who should take it? 

Only post-menopausal women. 

AIs are not FDA approved to lower breast cancer risk but are a good option to reduce breast cancer risk in post-menopausal women who may have an increased risk of blood clots or uterine cancer.

Common side effects: 

• hot flashes 
• vaginal dryness or irritation
• muscle and joint pain 
• fatigue
• elevated cholesterol levels 

Risks: 

• Can cause bone thinning which can lead to osteoporosis
• No increased risk of blood clots or uterine cancer, but research is ongoing regarding heart disease and osteoporosis 

How do I know which option is right for me?

You should have your risk assessed by a health care provider and then discuss your options for risk reduction with a provider who specializes in breast cancer risk reduction. Click here to learn more about the TriHealth High Risk Breast Program. 

Do I have to take medication?

While there is a known benefit to taking these types of medications for breast cancer risk reduction, they are not for everyone. It is important to discuss your exact risk with your provider and if one of these medications may be indicated. The choice is ultimately yours.

Contributing Author: Rebecca Beesley, MD, TriHealth Breast Care specialist

_References: 

_{American Cancer Society. Aromatase Inhibitors for Lowering Breast Cancer Risk. https://www.cancer.org/cancer/types/breast-cancer/risk-and-prevention/aromatase-inhibitors-for-lowering-breast-cancer-risk.html. Updated 12/16/2021. Accessed 6/6/2025.}

_{American Cancer Society. Deciding Whether to Use Medicine to Reduce Breast Cancer Risk. https://www.cancer.org/cancer/types/breast-cancer/risk-and-prevention/deciding-whether-to-use-medicine-to-reduce-breast-cancer-risk.html. Updated 5/5/2025. Accessed 6/6/2025.}

_{American Cancer Society. Tamoxifen and Raloxifene for Lowering Breast Cancer Risk. https://www.cancer.org/cancer/types/breast-cancer/risk-and-prevention/tamoxifen-and-raloxifene-for-breast-cancer-prevention.html
Updated 12/16/2021. Accessed 6/6/2025.}

_{Pederson HJ, Al-Hilli Z, Kurian AW. Reducing the risk of breast cancer. Cleve Clin J Med. 2022;89(11):643-652. Published 2022 Nov 1. doi:10.3949/ccjm.89a.21113}