'Breast screening could lead to overdiagnosis' - Study says

Contrary to belief that breast screening leads to fewer deaths, a United States study has found that they may not infact lead to fewer deaths but may lead to overdiagnosis.

Researchers reported that in areas of the US with high levels of screening, more tumors were diagnosed  but breast cancer death rates were no lower than in areas with fewer screenings.

Study lead, Charles Harding said the results were "far from definitive" but the most dramatic finding of the study was "the immediately evident - and substantial - evidence of breast cancer overdiagnosis"

For the new study, researchers analyzed breast cancer screenings, cancer diagnoses, tumor characteristics and deaths in 547 US counties.

The data came from nearly 16 million women living in those counties in 2000.

All were at least 40 years old, the percentage who had screening mammograms ranged from 39% to 78%, depending on where they lived.

Overall, a 10% point increase in breast cancer screenings was tied to a 16% increase in breast cancer diagnoses.
The number of screening mammograms performed did not, however, affect the number of breast cancer deaths.
Most of the additional cancers detected on screening were small tumors. There wasn't an increase in diagnosis of large, and presumably more advanced tumors.
Thus, the findings suggest breast cancer screenings lead to overdiagnosis because they mainly catch smaller tumors.
Stating that more research is needed, the research group said their "findings are quite tentative for mortality because the data are very noisy"
They however pointed out that the study raises important questions about the benefits of mammography screening, although "it certainly does not answer them."