Researchers from the Nordic Cochrane Center in Copenhagen, Denmark, have stated that one in three breast cancers that are discovered with mammograms are not life-threatening. They conclude that the treatments in one in three cases are unnecessary due to overdiagnosis of breast cancer.
Overdiagnosis is detection of cancer that is not life-threatening.
"In general, breast cancers come in three types: aggressive cancers that spread before they can be detected, cancers that spread slowly enough to be detected and treated early, and cancers that spread so slowly they pose no threat. Unfortunately, mammograms are best at detecting cancers in the latter category and not in the first two, and there is no way to distinguish the cancers from each other without watching them progress."
The researchers figure that out of every 2,000 women who have gotten mammograms on a regular basis for ten years, one woman will have been cured of cancer and ten will have been treated unnecessarily, even to the point of having chemotherapy, radiation and removal of one or both breasts.