The risk of breast cancer doubles in women who take hormone replacement therapy for five years, according to newly released results from the Women’s Health Initiative. This largest-of-its-kind study also made news in 2002 when the main part of the study was stopped after finding that hormone replacement was associated with higher risks of heart problems and breast cancer.

The new results confirm that taking the hormones estrogen and progestin after menopause increases the risk of breast cancer and demonstrates that risk increases with each year the hormones are taken. Taking the hormones for just two years increased the risk of breast cancer significantly, and after five years of hormones the risk of breast cancer is twice that of women who did not use hormone replacement.

The study also finds that after stopping hormone treatment, breast cancer risk falls as quickly as it rises. Roughly two years after stopping hormone treatment, the risk of breast cancer returns to normal levels. This is in stark contrast to other cancer risk factors such as smoking, which may take 10 to 15 years or more after quitting for cancer risk to return to normal.

This likely explains why breast cancer rates have plummeted in recent years. Following the original findings of the study, many women stopped taking hormone replacement therapy or decided not to start it: in the general population, use of hormone replacement has dropped 70 percent since the initial results were announced.

Some researchers have suggested that the decrease may not be due to fewer people taking hormones but instead because fewer women were getting mammograms. This would mean that fewer cancers were being detected, not necessarily that fewer were occurring.

However, the new study shows conclusively that mammography rates were virtually the same among those taking hormones and those not, putting to rest the idea that cancers are being missed due to reduced screening.

Doctors now caution women to consider using hormones only if their menopause symptoms are severe. The finding that breast cancer risk doubles with five years of hormone replacement is likely to reinforce the advice that only women who really need the treatment should use it. In addition, the fact that breast cancer risk seems to increase the longer the treatment is used will likely lead doctors to counsel their patients to limit hormone therapy treatment to the shortest possible course.

Despite the increased cancer risk, most women will not get breast cancer by taking hormones short-term. The increased cancer risk from a couple of years of hormone use translates to a few extra cases of breast cancer a year for every 1,000 women on hormones.

For some women, the transition to menopause can be very difficult, accompanied by severe hot flashes, memory problems, and difficulty sleeping. If these symptoms are interfering with your daily life, consider talking to your doctor about hormone replacement. While most women with mild symptoms should avoid hormone replacement, if your symptoms are severe, the increased cancer risk may be preferable to you in order to get some relief.

To find out more about hormone replacement, breast cancer screening and prevention, see the Healia Health Guide of Breast Cancer. If you have questions about hormone replacement, ask the experts on Healia Health Communities or share your experience at the Healia Health Community for Hormone Replacement Therapy.

_{Photo: merfam, Flickr, Creative Commons}