Breast cancer is the most commonly diagnosed cancer in American women. This year, the American Cancer Society estimates 212,920 cases of invasive female breast cancer will be diagnosed in the U.S. Another 61,980 cases of carcinoma in situ (a noninvasive, very early stage breast cancer) will occur.

Breast cancer is the second leading cause of cancer death for women (lung cancer is the leading cause). About 40,970 women are expected to die of the disease this year.

The risk for breast cancer increases with age. About 77 percent of women are older than 50 when they are diagnosed. Risk is higher among women with a family history of breast cancer, patients with a mutation known breast cancer genes (BRCA1 and BRCA2), patients who have had biopsy-confirmed abnormal cells in the breast duct or lobule, and women with a history of lobular carcinoma in situ.

Preventing Breast Cancer

Chemoprevention is the use of drugs to prevent disease. In the field of breast cancer, the first drug to show any prevention promise was tamoxifen. The Breast Cancer Prevention Trial showed women who took tamoxifen had 49 percent fewer cases of breast cancer than those taking a placebo. But doctors also found use of tamoxifen was associated with some potentially dangerous side effects, like increased risk for blood clots and endometrial cancer.

An important component in the fight to prevent breast cancer may lie with the hormone, estrogen. Prior to menopause, the hormone is mainly produced by the ovaries. As the ovaries stop functioning, levels of estrogen decrease. After menopause, the main source of estrogen production is non-glandular tissue, especially subcutaneous fat.

While estrogen is seen as important to female health, it also fuels the growth and development of some breast cancers. Researchers believe that lowering estrogen levels after menopause may reduce a woman's risk for breast cancer. The theory is being tested in the WISE (Women with Increased Serum Estradiol) Trial.

The WISE trial is studying the use of a drug called, letrozole (Femara®) in women at risk for breast cancer. Letrozole is a powerful nonsteroidal aromatase inhibitor. It reduces estrogen levels by inhibiting or inactivating the enzyme aromatase, which converts androgen hormones to estrogen. Studies show the medication inhibits 99 percent of estrogen biosynthesis.

The study will follow postmenopausal women 35 and older. Two-thirds of the participants will receive letrozole. One-third will take a placebo. Women will be seen every three months and receive exams, mammograms, measurements of bone density and blood tests.

Previous studies have shown letrozole to produce a partial response or stabilization of disease in 40 percent of women who already have advanced breast cancer. This is the first study to determine if the drug may prevent cancer in high risk women. Researchers say if the drug appears to be of benefit, larger scale studies will need to be done.

Experts caution the search for potential chemoprevention drugs needs to be approached cautiously. Doctors must carefully weigh the risk of side effects against the benefits of treatment. Rare side effects associated with letrozole include bone weakening and elevation in cholesterol levels.

For information about the WISE Trial, call Hannah Green, MPH at (617) 632-2359, or e-mail her at hannah_green@dfci.harvard.edu. Information is also available on the web at http://www.dfci.harvard.edu/pat/cancer/breast-ovarian/wise.asp.

For general information on breast cancer:

American Cancer Society

National Cancer Institute