1.3 mil. overdiagnosed for breast cancer in US: study
November 24, 2012, 12:26 am TWN
WASHINGTON -- More than a million U.S. women have received unnecessary and invasive cancer treatments over the last 30 years, thanks to routine mammograms that detected harmless tumors, scientists said Thursday.
The results throw new doubt over the effectiveness of an already controversial cancer-screening tool that is aimed at detecting tumors before they spread and become more difficult to treat.
To reach the 1 million figure, researchers compared the number of breast cancer cases detected at early and late stages among women over 40 between 1976 and 2008.
Their analysis showed that, since mammograms became standard in the United States, the number of early stage breast cancers detected has doubled — in recent years, doctors found tumors in 234 women out of 100,000.
But in that same period, the rate of women diagnosed with late-stage breast cancer has dropped just 8 percent — from 102 to 94 cases out of 100,000.
"We estimated that breast cancer was overdiagnosed — i.e., tumors were detected on screening that would never have led to clinical symptoms — in 1.3 million U.S. women in the past 30 years," authors Gilbert Welch of Dartmouth Medical School and Archie Bleyer of the Oregon Health & Science University, wrote in a study published Thursday in the New England Journal of Medicine.
"We estimated that in 2008, breast cancer was overdiagnosed in more than 70,000 women; this accounted for 31 percent of all breast cancers diagnosed," they added.
These women likely received major medical interventions — including surgery, radiology, hormone therapy and chemotherapy — that ought only to be used when absolutely necessary, the authors stressed.
They also concluded the significant drop in breast cancer deaths can be best explained by the improvement in treatments, rather than the early detection through mammograms.
The research adds to other work published in recent years that throw into question whether mammograms ought to be performed regularly as a cancer prevention tool.
One often cited study, done in Norway, showed that regular mammograms reduce the risk of death from breast cancer by less than 10 percent.