On Apr. 18, 2007, a study led by the University of Texas M.D. Anderson Cancer Center reported that the sharp decline in the rate of new breast cancer cases in 2003 may be related to a national decline in the use of hormone replacement therapy (HRT).

Age-adjusted breast cancer incidence rates in women in the U.S. fell 6.7% from 2002 to 2003. The two most commonly prescribed forms of HRT in the U.S., Premarin and PremproTM, had their steepest declines starting in 2002-2003 — from 61 million prescriptions written in 2001 to 21 million in 2004.

The study was published in the New England Journal of Medicine.