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Breast cancer risk – I can take a drug for that?

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Q: I went in for my annual screening mammogram at age 45. I filled out a questionnaire before going in. The report said that although the images were negative for cancer or other concerning findings, I may be at high risk of breast cancer. What should I do?

A: The good news is, there are options for you and others at high risk of breast cancer.

Breast cancer risk is based on hormonal history, family history, previous breast issues and breast density. Any health care provider can use a calculator to evaluate your risk compared with that of the general population.

The two most commonly used tools are the Breast Cancer Risk Assessment Tool (BCRAT) and the International Breast Cancer Intervention Study (IBIS) risk calculator. Both are available online, but entering the complete data into them can be time-consuming.

A quicker alternative is the United States Preventive Services Task Force (USPSTF) method, which considers risk factors such as having one or more first-degree relatives (such as a parent or sister) with breast cancer — particularly relatives who experienced breast cancer before going through menopause — or a diagnosis on biopsy of high-risk pathology, such as atypical hyperplasia or lobular carcinoma in situ.

If one of these tools identifies you as being at high risk, what should you do?

First, talk to your doctor. Discuss and decide your most appropriate breast-imaging screening options going forward — whether that is to continue annual mammograms or add other studies as well. Of course, you’ll be encouraged to continue regular preventive health visits, which will often include a clinical breast exam. Depending on your family history, you may also need to meet with a genetic counselor to consider genetic testing.

Finally, and perhaps most surprising, your doctor may ask you to consider a risk-reducing medication, such as the selective estrogen receptor modulator (SERM) tamoxifen or raloxifene (Evista) or an aromatase inhibitor, such as exemestane (Aromasin) or anastrozole (Arimidex). Women age 35 and older who are at a high risk of breast cancer are eligible for these risk-reducing medications, sometimes called chemoprevention.

For premenopausal women, the only option is tamoxifen. The standard dose of tamoxifen is 20 milligrams daily for five years. You may alternatively be prescribed a dose of 10 milligrams. Research is underway to confirm whether the lower dose is equally effective and the length of time women should take it.

Risks of tamoxifen include increased likelihood of blood clots (thromboembolic events), which is higher in older women. Women taking tamoxifen to reduce their risk of breast cancer are twice as likely to develop a blood clot compared with peers not taking the medication. Still, the risk is quite low (1.2% compared with 0.48%). The risk of blood clots also increases with age and in women taking estrogen-based birth control, such as hormonal contraceptive pills. There is also a risk of endometrial cancer, although only in postmenopausal women taking tamoxifen. The side effects of tamoxifen include hot flashes, menstrual irregularities and increased risk of cataracts.

In postmenopausal women, there are additional options, including raloxifene and the aromatase inhibitors.

Raloxifene is similar to tamoxifen. It is Food and Drug Administration approved for osteopenia and osteoporosis. It has similar side effects as tamoxifen, but the risks are less prominent. Raloxifene has the added benefit of increasing bone strength and can be taken for greater than five years for bone health.

Aromatase inhibitors — exemestane and anastrozole — are pills taken once daily. Side effects may include bothersome hot flashes or joint pain, which can be severe. They have the risk of decreasing bone strength, so bone mineral density should be monitored.

Aromatase inhibitors are preferred in women with a uterus or a history of blood clots in deep veins (deep vein thrombosis) or a blockage in one of the pulmonary arteries in the lungs (pulmonary embolism). Raloxifene and tamoxifen may be better options in women with osteoporosis. All these medications are 40% to 65% effective at reducing the risk of invasive breast cancer. Talk to your primary care doctor or a breast specialist to learn more about these options.

Liz Gilman, M.D.

Dr. Gilman is an internist in the Consultative Medicine Clinic and Breast Diagnostic Clinic in Rochester, MN.

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