• Health & Wellness

    What Are the Benefits and Risks to Taking Medication To Prevent Cancer Recurrences?

August 5, 2011

Dear Mayo Clinic:

Three months ago at age 70 I had a bilateral mastectomy for invasive lobular cancer. Pathology reports indicated that I am cancer free. I currently take anastrozole, which I was told will lessen my chance of recurrence by 7 percent. However, the side effects I'm experiencing, including thinning hair and an increased risk of osteoporosis, don't seem worth it. Are there other things I should consider?


When considering whether to have additional treatment (adjuvant therapy) following successful cancer treatment, weighing the pros and cons, including possible side effects, is a sensible approach. Anastrozole is often used to treat breast cancer in postmenopausal women and, as in your case, it may be recommended to help decrease the risk of breast cancer returning. In some women, anastrozole can cause the side effects you mention — as well as joint aches — but those side effects are uncommon. If you prefer not to take anastrozole, you have other options.

Many breast cancer tumors are sensitive to estrogen. Anastrozole is one in a group of medications that stop the body from making estrogen after menopause. Less estrogen in your body makes it less likely that your prior cancer will return and less likely that a new breast cancer tumor will develop. These drugs, called aromatase inhibitors, block the action of an enzyme that converts androgens in the body into estrogen. They are effective only in postmenopausal women. Based on a woman's individual circumstances regarding her breast cancer, her overall health and other medical conditions, taking a medication such as anastrozole can decrease the chance of breast cancer recurring by about 7 to 10 percent.

Some people have significant side effects when taking anastrozole. But fortunately that doesn't happen often. Many women who take this medication tolerate it well and don't notice any side effects. If serious side effects occur as a result of taking anastrozole, though, or if you have less-significant side effects that are bothersome enough to interfere with your day-to-day activities, alternative medications are available.

Two other aromatase inhibitors, exemestane and letrozole, can be used instead of anastrozole to help reduce your risk of breast cancer recurrence. Although the side effects associated with these drugs can be similar to those of anastrozole, people who cannot tolerate one medication often have fewer side effects with a different medication. So switching to exemestane or letrozole could help decrease the side effects you may experience with anastrozole.

If you prefer not to take any type of aromatase inhibitors, there is another option as well. A class of medications known as selective estrogen receptor modulators can also be used to lessen your risk of breast cancer recurrence. These medications work by blocking estrogen from attaching to the estrogen receptors on cancer cells. They can be used in women both before and after menopause. Tamoxifen is the most commonly used selective estrogen receptor modulator. Keep in mind, though, that selective estrogen receptor modulators can have their own side effects, too.

To make a decision about what's right for you, talk to your doctor. Before you make any final decisions, carefully discuss and consider the risks versus benefits of taking these medications to reduce your cancer risk. And remember that you always have the option of not pursuing any further therapy. For some women, this can be a quite reasonable choice.

— Timothy Moynihan, M.D., Oncology, Mayo Clinic, Rochester, Minn.