SAN ANTONIO, TX – Women who use certain types of hormones after menopause still have an increased risk of developing breast cancer nearly two decades after they stop taking the pills, long-term results from a big federal study suggest.
Although the risk is very small, doctors say a new generation of women entering menopause now may not be aware of landmark findings from 2002 that tied higher breast cancer rates to hormone pills combining estrogen and progestin.
"The message is probably not clear" that even short-term use may have lasting effects, said Dr. Rowan Chlebowski of Harbor-UCLA Medical Center in Torrance, California. He discussed the new results Friday at the San Antonio Breast Cancer Symposium.
The results are from the Women's Health Initiative, a federally funded study that tested pills that doctors long thought would help prevent heart disease, bone loss and other problems in women after menopause. More than 16,000 women ages 50 to 70 were given combination hormone or dummy pills for five to six years.
The main part of the study was stopped in 2002 when researchers surprisingly saw more heart problems and breast cancers among hormone users. Women were advised to stop treatment but doctors have continued to study them and have information on about two-thirds.
With roughly 19 years of followup, 572 breast cancers have occurred in women on hormones versus 431 among those on dummy pills. That worked out to a 29% greater risk of developing the disease for hormone takers.
Still, it was a difference of just 141 cases over many years, so women with severe hot flashes and other menopause symptoms may decide that the benefits of the pills outweigh their risks, doctors say. The advice remains to use the lowest possible dose for the shortest time.
Why might hormones raise breast risk?