Medications to Prevent Breast Cancer
Women who should consider using these endocrine therapies are those who fall into the high risk categories. Women with known genetic mutations that lead to breast cancer who have not undergone a prophylactic mastectomy are clearly candidates for this therapy. The most commonly recognized mutations are BRCA1 and BRCA2. Women who have been diagnosed with ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS) and those with atypical hyperplasia especially over the age of 35. Women ages 35-59 who have a calculated 5 year breast cancer risk of 1.66% should be counseled on this option for prevention. Finally all women over the age of 60 should be considered.
Selective estrogen receptor modulators were the first to be widely used. The most commonly used are Tamoxifen and Raloxifene. They work by blocking estrogen receptors in the breast preventing the proliferative effect of estrogen on this tissue. In other tissues they may act as receptor activators, simulating estrogen thereby producing estrogen like effects. The other type of medication is aromatase inhibitors which are relatively new and act by decreasing the circulating levels of estrogen in postmenopausal women.
Tamoxifen is the most commonly used medication to prevent primary and recurrent breast cancer. It decreases the risk of developing cancer by 50%. It has anti-estrogen effects in the breast but agonistic effects in the uterus and other tissues. Women who take this medication have a higher risk of developing endometrial cancer and should be monitored appropriately. Women who take this medication also have an increased risk of venous thromboembolism such as a deep vein thrombosis, pulmonary embolism and stroke.
Raloxifene was initially approved for the prevention of osteoporosis because of its agonist effects on the bone helping to maintain density. Like Tamoxifen it has an antagonist effect on the breast reducing the incidence of invasive breast cancer by 72% at 4 years and 66% by 8 years. The major bothersome side effects are hot flashes and leg cramps. There is also an increased risk of venous thromboembolism.
The aromatase inhibitors include Letrozole, Anastrazole and Exemestane. They block an enzyme which normally functions to convert precursors to estrogens. This therapy is effective in postmenopausal women, lowering the circulating levels of estrogen. In women who are still menstruating there is an opposite effect and therefore this is not recommended for breast cancer treatment or prevention in premenopausal women. The side effects are therefore the typical low estrogen ones such as hot flashes, genital dryness, arthralgia and low bone density. The risk of venous thromboembolism and endometrial cancer is not increased.
Continued research has provided revolutionary therapies for the treatment of breast cancer improving the survival rate dramatically over the past decade. This is excellent news for the 11% of women who will develop breast cancer. Prevention however is still the ideal since no one should have to go through the anxiety, pain and fear associated with a diagnosis of breast cancer. You should see your gynecologist regularly and know your family history. Your doctor can help you asses your risk of breast cancer and direct you to the appropriate provider so you can get the care you deserve.
I hope this article has provided you with information that will help you make wise choices, so you may:
Live healthy, live well and live long!
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