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A controversial study claims one-third of breast cancer patients are treated unnecessarilyby Mike Denison

A study published Monday in the Annals of Internal Medicine argues that mammograms can be unnecessary and dangerous, even for women who actually have breast cancer.

The study's authors argue mammograms can find small tumors that are actually harmless, so one in three women could get chemo that puts them in danger rather than saving their lives. 

Some experts decried the study, saying such "overdiagnosis" is relatively rare, Kaiser Health News reports.

"By treating all the cancers that we see, we are clearly saving some lives. But we're also 'curing' some women who don't need to be cured."

Otis Brawley, American Cancer Society

Dr. Otis Brawley, chief medical officer of the American Cancer Society, was not involved in the study but wrote an editorial supporting it.

'Articles like this aren't very helpful'

Dr. Debra Monticcolo, chair of the American College of Radiology's Commission on Breast Imaging, blasted the study and said overdiagnosis is too rare to pose a real threat.

"Articles like this aren't very helpful," she said. ACR recommends yearly mammograms starting at age 40. The ACS recommends yearly mammograms from age 45 to 54, then every other year after that.

Breaking down the study

The Danish study compared the rate of diagnosis before and after Denmark started offering mammograms. If mammograms were working as intended, the number of both small-scale and large-scale tumors should fall. However, the study found only the number of early-stage tumors dropped, implying current medical technology may lead doctors to over-diagnose. 

Fran Visco of the National Breast Cancer Coalition said unnecessary radiation can damage the heart or, in some cases, actually cause cancer.