Breast cancer rates dropped immediately after a major study in 2002 cast doubt on the wisdom of hormone supplements for menopause, and prompted millions of women to stop taking them.
"An awful lot of breast cancer was caused by doctors' prescriptions," Larry Norton of Memorial Sloan-Kettering Cancer Center in New York, tells Rob Stein of the Washington Post. "That's a very serious and sobering thought."
Stein writes, "The findings also help explain one of the biggest mysteries about breast cancer -- why the number of cases rose steadily for decades."
"This is colossal," said Rowan Chlebowski of the Harbor-UCLA Medical Center, who helped conduct the analysis. "It translates into thousands of fewer breast cancers that have been diagnosed in women in the United States and could be in the future."