Exemestane May Reduce Breast Density in High Risk Postmenopausal Women

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Having dense breast tissue on mammogram is believed to be a strong predictor of breast cancer. Researchers from Georgetown Lombardi Comprehensive Cancer Center have found that exemestane, a drug used to treat early breast cancer in postmenopausal women, may reduce mammographic breast density in the same group of women.

A preliminary analysis on the small phase II study was presented at the 33rd Annual CTRC-AACR San Antonio Breast Cancer Symposium.

Jennifer Eng-Wong MD MPH, an assistant professor of oncology at Georgetown Lombardi, analyzed data from the first 23 of 42 women enrolled in the study. The women who were eligible for the study had an increased risk of breast cancer because of one of several factors, including a high-risk breast lesion (lobular neoplasia or ductal carcinoma in situ), a known BRCA 1/2 mutation, or a prior stage I/II breast cancer with treatment completed at least two years prior to study enrollment.

Mammograms were taken before the women started taking exemestane and one year after treatment. Breast density was compared between the two mammograms for each woman.

Read: Breast Density and Weight Gain Both Risk Factors for Breast Cancer

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Exemestane (Aromasin) is in a class of medications called aromatase inhibitors. These work by decreasing the amount of estrogen produced by the body, leading to the slowing or halting of some breast tumors that need estrogen to grow.

Eng-Wong reports that the researchers saw a seven percent decrease in mammographic density among the women, what she calls a “statistically significant finding.”

But she also notes that previous studies of aromatase inhibitors have not shown a significant decline in breast density in high-risk women. Other studies have also included tamoxifen, another FDA-approved drug used to reduce breast cancer risk, but with significant side effects. In addition, at this stage of the study, analysis of a control group (women not taking exemestane) has not yet been included.

A separate study on exemestane was also released during the Breast Cancer Symposium. The drug was compared to another aromatase inhibitor, Arimidex, on its ability to reduce the risk for breast cancer recurrence and death from breast cancer.

Read: Cymbalta May Help Relieve Breast Cancer Treatment Pain

Principle investigator Paul Goss MD from the Massachusetts General Hospital Cancer Center in Boston said that the large MA27 trial involving over 7500 postmenopausal women found no significant difference in the two therapies. However, because exemestane is still patented, the cost is significantly higher than anastrozole.

The two drugs also have different adverse effect profiles. Exemestane, because it is a steroid based medication, was associated with more cases of acne and masculinization and with elevated levels of liver enzymes and bilirubin. However, the drug was less likely than anastrozole to produce vaginal bleeding, hypertriglyceridemia, hypercholesterolemia, or self-reported osteoporosis.

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