In a new UCSF study of more than 2 million mammogram screenings performed on nearly 700,000 women in the United States, scientists for the first time show a direct link between reduced hormone therapy and declines in ductal carcinoma in situ (DCIS) as well as invasive breast cancer. The researchers saw such a striking decrease, they believe they also have uncovered indirect evidence that hormones promote breast tumor growth.
The declines occurred in the age groups that most widely embraced then abandoned hormone therapy.
For nearly a decade, postmenopausal women have been strongly advised to refrain from long-term hormone therapy or to use the lowest dose possible for the shortest time to relieve hot flashes and night sweats. Numerous studies have suggested that women taking a combination of progestin and estrogen faced a higher risk of breast cancer and other potential health hazards.
The new findings suggest that hormones helped promote breast tumor growth of preexisting, clinically latent hormone-dependent cancers, not only increasing the incidents of invasive cancer, but also the risk of ductal carcinoma in situ (DCIS).
"We show that the incidence of breast cancer decreases if you take the hormones away,'' said senior author Karla Kerlikowske, MD. "The fact that we're continuing to see a decrease in invasive cancer means that the effects of stopping the hormones may be long-lasting.''
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