Breast Cancer Prevention in High-Risk Individuals

Breast cancer affects around 250,000 women in the U.S. every year, prompting a critical look at preventive measures for those at increased risk. This blog explores the effectiveness of Selective Estrogen Receptor Modulators (SERMs) like tamoxifen and raloxifene, and Aromatase Inhibitors (AIs) such as anastrozole and exemestane, in reducing breast cancer risk. While SERMs block estrogen's effects on breast tissue, AIs reduce estrogen production in postmenopausal women, targeting hormone-responsive tumors. Despite their potential, the use of these medications is carefully considered due to side-effects and specific eligibility criteria, including age, family history, and the presence of precancerous conditions. The blog also addresses the importance of informed decision-making, especially for women with a significant risk based on factors like lobular carcinoma in situ (LCIS) or atypical hyperplasia, and the need for ongoing dialogue with healthcare providers to navigate the options for breast cancer prevention effectively.


Breast cancer affects approximately 250,000 women in the United States annually. Understanding the risk factors, such as age, family history, and precancerous conditions like lobular carcinoma in situ (LCIS) or atypical hyperplasia, is crucial. For women at increased risk, healthcare providers may recommend medication as a preventive measure. This article explores the options, their effectiveness, and considerations for women contemplating these therapies.

Risk Reduction through Medication

Two primary types of medications are considered for breast cancer prevention: Selective Estrogen Receptor Modulators (SERMs) and Aromatase Inhibitors (AIs). SERMs, including tamoxifen and raloxifene, block estrogen's effects on breast tissue. AIs like exemestane reduce estrogen production in postmenopausal women. These medications target tumors responsive to female hormones, identifiable by hormone receptors (ER-positive or PR-positive).

SERMs: Tamoxifen and Raloxifene

Studies show that tamoxifen can significantly reduce the risk of developing hormone-positive breast cancers in at-risk women. Despite its efficacy in reducing breast cancer risk by about one-third, tamoxifen is not widely used for prevention due to its lack of impact on survival rates and potential risks, such as uterine cancer and blood clots. Raloxifene, primarily used for osteoporosis, has shown promise in reducing invasive hormone-positive breast cancer risk in postmenopausal women. Though slightly less effective than tamoxifen, raloxifene has fewer serious side-effects, such as a lower risk of uterine cancer.

 Aromatase Inhibitors: A Potential Alternative

Anastrozole and exemestane, two AIs, have shown a 50% reduction in breast cancer risk compared to placebo in postmenopausal women. These findings suggest AIs as a viable alternative to SERMs. However, AIs are not yet FDA-approved for breast cancer prevention in the US, and questions about their long-term effects on bone health and cardiovascular risk remain. Additionally, joint and muscle symptoms may deter some women from choosing AIs.

Precautions and Monitoring

Tamoxifen and raloxifene are not suitable for everyone. They are generally not recommended for women with a history of blood clots, those on blood thinners, smokers, orthose who are pregnant, planning to become pregnant, or breastfeeding. Nonhormonal birth control methods are advised for women using tamoxifen pre-menopause. Close monitoring by healthcare providers is essential for those on these medications. Women should report any abnormal gynecologic symptoms and seek immediate care if they experience signs of a blood clot.

Who Should Consider Medication for Breast Cancer Prevention?

Breast cancer prevention medication is an important topic for women who are at higher risk of developing the disease. Expert guidelines suggest discussing the risks and benefits of such medication with both premenopausal and postmenopausal women who fall into this category. Typically, these discussions are recommended for women aged 35 and above who meet certain risk criteria.

Identifying High-Risk Candidates

Women who may benefit from preventive medication include those with a history of lobular carcinoma in situ (LCIS) or atypical hyperplasia. These conditions, though not cancerous, can increase the risk of developing breast cancer.

Another group of women who should consider prevention medication are those with a calculated five-year breast cancer risk of 1.66 percent or higher. This risk assessment is often determined using the Gail model. This model takes into account factors such as a woman's age, age at her first menstrual period, age at first livebirth, the number of first-degree relatives with breast cancer, and the history and results of past breast biopsies.

Using the Breast Cancer Risk Assessment Tool

The Breast Cancer Risk Assessment Tool, based on the Gail model, is available to help women calculate their personal risk of breast cancer. However, it's crucial to discuss the results with a healthcare provider for accurate interpretation. Remember, having risk factors does not guarantee the development of cancer; it only indicates a higher likelihood.

The Gail Model's Limitations

One significant limitation of the Gail model is that it does not account for cancer risks associated with gene mutations, particularly in the BRCA1 and BRCA2 genes. While there is limited data suggesting that tamoxifen may reduce breast cancer risk in women with BRCA mutations, more research is needed before it becomes a routine recommendation for these individuals.

Choosing the Right Medication

Breast cancer prevention involves making informed decisions about medication, especially for women at higher risk. These decisions are significantly influenced by whether a woman is premenopausal or postmenopausal, as each stage presents different considerations and options.

For Postmenopausal Women: Understanding Your Choices

If you are a postmenopausal woman considering breast cancer prevention, your options include Selective Estrogen Receptor Modulators (SERMs) and Aromatase Inhibitors (AIs).

  • SERMs like tamoxifen and raloxifene work by blocking estrogen's effects on breast tissue. While tamoxifen has shown to be more effective in preventing breast cancer, raloxifene is associated with fewer severe side effects.
  • Aromatase Inhibitors  (AIs) reduce the body's estrogen production. They are endorsed by some professional organizations for prevention purposes, but it's important to note that they are not FDA-approved for this use in the U.S. AIs' long-term impact on bone health and cardiovascular risk remains a subject for further research.

For Premenopausal Women: A Focused Approach

As a premenopausal woman, your options for breast cancer prevention medication are more specific. Tamoxifen is currently the only recommended preventive medication for women in this group. Here's why:

  • Tamoxifen has been proven effective in reducing the risk of developing hormone-responsive breast cancer.
  • Raloxifene, while beneficial for postmenopausal women, lacks sufficient safety data for premenopausal women and is not recommended.
  • AIs are generally not used in premenopausal women as they can increase estrogen production, which is counter productive for prevention in women whose ovaries are still active.

Overall, the choice of medication for breast cancer prevention hinges on your menopausal status. Postmenopausal women have a choice between SERMs and AIs, considering the efficacy and side effects. For premenopausal women, tamoxifen remains the go-to option. It's essential to have a detailed discussion with your healthcare provider, considering your personal health profile and the most up-to-date medical advice, to make the decision that's right for you.


For women at a heightened risk of breast cancer, considering preventive medication is a significant decision. It involves weighing the potential benefits against the risks and side-effects. These conversations with healthcare providers are vital in making informed choices about breast cancer prevention.