Hormone replacement therapy drugs can increase patient's risk for breast cancer

Published on July 14, 2008 4:50 AM

Researchers reported that three years after women stopped hormone replacement therapy, they began to take the hormone drugs. After a full investigation researchers found that women who took the drugs still had a 27% higher risk of developing breast cancer than those who took a placebo.

Hormone drugs can increase patients' risk for heart disease, stroke and breast cancer. Although the heart risks eased after the women stopped taking the drugs, their overall cancer risk remained 24% above average.

"Menopausal women really need to think through whether using estrogen-progestin is the right thing to do, particularly if continued for more than a few years," said Marcia L. Stefanick, a professor of medicine at Stanford University.

The researchers surveyed 16,608 women with an average age of 63 who were given either Prempro (a mix of estrogen and progestin) or a placebo. The goal was to determine whether the hormones could protect against heart disease.

But the study was stopped prematurely after an average of 5.6 years when it was determined that women taking the hormones had a 26% higher risk of breast cancer as well as an increased risk of stroke, blood clots and heart attack.

Subsequent analysis, however, showed that younger women beginning treatment at menopause about 50 did not share the increased risk. Menopause is the period in a woman's life when her ovaries stop releasing egg cells and begin to make smaller amounts of the 2 main female hormones, estrogen and progesterone.

Lowered hormone levels cause the symptoms that are often associated with menopause - hot flashes, dryness and thinning of vaginal tissues, and mood swings. Low estrogen levels also increase a woman's risk of other health problems, such as osteoporosis.

The new study, funded by the National Heart, Lung and Blood Institute, followed 15,730 of the original trial participants for an average of three years after they stopped taking hormones.

The researchers found 281 cancers in the group receiving Prempro, compared with 218 in the placebo group, a difference driven primarily by breast cancers. The rate of deaths from all causes was 15% higher in the Prempro group, but the difference was not considered statistically significant.