All Cancers Breast Cancer Cancer Risk & Prevention

Using Medicine to Reduce Breast Cancer Risk

Medically Reviewed by Brian S. Englander, MD

Written by Vanessa LeongJan 2, 20248 min read

Source: Shutterstock

To reduce the risk of breast cancer, certain medications can be used as a preventative measure, known as chemoprevention. It is a suitable option for individuals who have a higher-than-average risk of developing breast cancer. Nevertheless, one must consider the potential side effects before deciding to take them. Ultimately, the benefits of any treatment or prevention plan should outweigh its limitations and negative effects to have an overall positive impact.

Types of medicines to reduce breast cancer risk

Currently, only a few medicines available in the US have shown to be effective in reducing breast cancer risk. They can be grouped into two categories.

Selective Estrogen Receptor Modulators (SERMs)

SERMs work by blocking estrogen (a natural hormone in the body that is used by some breast cancers to grow). Some breast cancer cells have a place on them called a receptor, where estrogen can attach. This type of cancer cell requires estrogen to grow. SERMs work by attaching themselves to these receptors so estrogen cannot attach to the breast cancer cells, preventing them from multiplying and growing. This type of breast cancer is called estrogen-receptor-positive cancer. The approved SERMs are:

Tamoxifen
Raloxifene

However, not all breast cancers have this receptor. Those breast cancers are called estrogen-receptor-negative cancers. SERMs do not reduce the risk for these types of cancers.

Learn more: Breast Cancer Hormone Receptor Status

Aromatase Inhibitors (AIs)

AIs work by lowering estrogen levels in the body. An enzyme called aromatase is present in several organs in the body, including the breast. Aromatase assists in the production of estrogen by converting other hormones into estrogen. AIs work by stopping aromatase from converting other hormones into estrogen, thereby lowering the body’s estrogen. Before menopause, the ovaries produce most of the estrogen in a female’s body. However, after menopause, the ovaries stop producing estrogen, and aromatase becomes the primary contributor to the production of estrogen. Therefore, AIs are mainly recommended for individuals who have gone through menopause for both chemoprevention and treatment.

The approved AIs are:

Anastrozole (Arimidex®)
Exemestane (Aromasin®)
Letrozole (Femara®)

Similar to SERMs, AIs only work for hormone-receptor-positive breast cancer.

Side effects of using medicine to reduce breast cancer risk

These medicines, while proven to be effective, do have side effects and possible risks.

Medicine type	Possible side effects	Precautions
SERMs (such as Tamoxifen and Raloxifene)	Menopausal symptoms (hot flashes, night sweats, vaginal dryness, and vaginal discharge) Increases risk of developing blood clots (overall risk is less than 1% in average cases) It may increase the risk of heart attack or stroke Tamoxifen can increase the risk of cancers of the uterus (less than 1% and goes back to normal within a few years of stopping the drug, tends to only affect women over 50)	Pre-menopausal individuals may experience menstrual changes, and some may go into menopause. Individuals with a history of blood clots are usually not recommended to take this drug. Those with a history of a heart attack or stroke or an increased risk for them may also not be recommended this drug.
AIs	Menopausal symptoms (hot flashes, night sweats, vaginal dryness, and vaginal discharge) It may cause muscle and joint pain It may speed up bone thinning, which can lead to osteoporosis May raise cholesterol	It is often recommended to check bone density before starting one of these drugs. Those with pre-existing heart disease may not be suitable to take these drugs as they may be at a higher risk of heart problems

Who should use medicine to reduce breast cancer risk

Due to their side effects and possible risks, medicine used to reduce breast cancer risk is generally not recommended to the average population with average risk. These medicines are recommended more for individuals with high risk. Individuals are considered to have an increased risk when they have certain important risk factors that make them prone to getting breast cancer. Seeing a healthcare professional would be the first step in assessing your breast cancer risk. They would normally take into account factors such as:

Your age
Personal history of breast cancer
Medical history
Family history of breast cancer
Having a gene mutation linked to breast cancer (or any other type of cancer)

If you are assessed to have a high risk of developing breast cancer, your doctor may recommend taking one of these drugs to lower those risks.