Breast cancer drug cuts risk of second cancer

NEW YORK (Reuters Health) - In premenopausal women with breast cancer, taking the breast cancer drug tamoxifen significantly reduces the risk of developing a second cancer in the other breast, according to a Swedish study.

This is the first study to show this in younger, premenopausal women, Dr. Lisa Ryden from Lund University Hospital and colleagues note in the latest issue of the European Journal of Cancer.

Tamoxifen is commonly used to treat and prevent breast cancer. The drug slows or stops the growth of cancer cells present in the body. It helps keep the original breast cancer from recurring and helps prevent new cancer in the opposite breast. It also cuts the risk of breast cancer in women at high risk for developing the disease.

Ryden's team studied 564 premenopausal women treated for breast cancer who then received either 2 years of tamoxifen or no additional treatment (the control group).

They report that 17 women taking tamoxifen developed a second cancer in the opposite breast, what doctors call contralateral breast cancer, compared with 35 women in the control group who were not taking tamoxifen.

The median time to the second cancers was 4 years. The women who did not develop contralateral breast cancers were followed for a median of 14 years.

The untreated women, regardless of age, had a 12 percent risk of developing a contralateral breast cancer during a median of 14 years, and in women younger than 40 the risk rose to 20 percent, the researchers report.

Tamoxifen for 2 years reduced this risk by 50 percent for the overall group and by 90 percent in women younger than age 40, they found.

Tamoxifen significantly reduced the risk of contralateral breast cancer in all women regardless of age, Ryden and colleagues note.