DEAR MAYO CLINIC:

My sister, who is 47, has been diagnosed with early-stage breast cancer. Her doctor recommends she take tamoxifen for five years after her lumpectomy and radiation treatment. Why is this necessary? We don't have a family history of breast cancer.

ANSWER:

Tamoxifen is a type of anti-estrogen hormone treatment that can be used to treat breast cancers sensitive to hormones. These kinds of breast cancers are referred to as hormone receptor positive. Tamoxifen, and other anti-estrogen drug treatments, can be used to help prevent cancer from coming back in the same area after a tumor has been removed, as well as decrease the risk of cancer developing in other tissue. Regardless of a woman's family history, tamoxifen can be a useful treatment for hormone receptor positive breast cancer.

Doctors typically treat women who have early-stage breast cancer with the intent of curing the disease. Treatment routinely involves local and regional therapy, such as surgery with or without radiation. With that therapy, some patients are cured. But even if all the known cancer is surgically removed, some breast cancer cells may be left behind somewhere in the body that could grow and cause trouble.

A number of factors can help predict an individual patient's risk for developing breast cancer recurrence following removal of all the known disease. These include the size of the cancer, the grade of the cancer -- basically, how aggressive it looks under a microscope -- and whether lymph nodes are involved with the cancer.

For patients who have a very low risk of recurrence, no systemic drug therapy is generally recommended. However, for patients who have higher risk of cancer recurrence, drug therapy can be a way to decrease the risk of recurrent breast cancer or death from the disease.

Systemic drug treatment consists of three major classes: hormone treatment (such as tamoxifen or other estrogen-suppression treatments), antibody treatment (such as trastuzumab, also known as Herceptin), and chemotherapy. In your sister's situation, tamoxifen was most certainly recommended as a result of her cancer cells having hormone receptors on them because, as referred to above, tamoxifen is only useful for this type of cancer.

If she has questions, your sister should discuss with her doctor her risk of cancer recurrence and the potential benefits of hormone therapy. Before taking tamoxifen, she should also understand the risks that may be involved.

For example, if she hasn't reached menopause, your sister may want to talk with her doctor about appropriate birth control options during hormone treatment for breast cancer. Women taking tamoxifen shouldn't become pregnant because the medication may harm the fetus. A form of birth control that doesn't involve hormones is typically recommended during hormone therapy and for approximately two months after treatment is complete.

In addition, although many women don't experience side effects from hormone therapy, some side effects are possible. Common side effects of tamoxifen may include hot flashes, vaginal discharge, and irregular menstrual periods in premenopausal women. More serious, although less common, side effects include blood clots and uterine cancer.

After a comprehensive discussion of the risks and benefits with her doctor, your sister will be in a better position to understand and evaluate the rationale for considering cancer therapies such as tamoxifen.

-- Charles Loprinzi, M.D., Oncology, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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