In February 2008, a new study revealed that women who take combined hormone therapy drugs, like Wyeth?s Prempro, for at least five years face a greater risk of having abnormal mammograms and breast biopsies.

The study of nearly 17,000 women was split nearly down the middle, with half receiving hormone therapy consisting of estrogen and progesterone, and the other half receiving a placebo. The study found that women taking the hormones were 12 percent more likely to have abnormal mammograms and 3.9 percent more likely to have abnormal breast biopsies than women receiving the placebo.

While researchers do not have a definitive answer as to why the hormone therapy drugs provoke abnormalities, they theorize it may be due to the increase in breast density resulting from taking hormones.

?This is really definite evidence that hormones interfere with breast cancer diagnosis,? said Los Angeles Doctor Rowan Chlebowski. ?We have other imaging techniques, and this could be a signal that we need more of that research.?

Source: Anna Boyd, ?Hormone Therapy linked to a higher risk of abnormal mammograms,? eFluxMedia, February 26, 2008.