The potential for over-diagnosis and over-treatment from too many mammograms too early has become the subject of a recent study.

The Norwegian Study included nearly 40,000 women with invasive breast cancer.

The study allowed the researchers to compare the rate of breast cancers diagnosed through mammograms and those found because a tumor was palpable or produced symptoms.

Norway has data on virtually all women who get a diagnosis of breast cancer.

The researchers concluded that 15 percent to 25 percent of breast cancers were overdiagnosed — meaning 6 to 10 women were overdiagnosed for every 2,500 offered screening mammograms.

– Dr. Joanne Elmore of the University of Washington and Dr. Suzanne Fletcher of Harvard, in an editorial
Under current practice, those women get biopsies and treatment for breast cancers that would never have been detected otherwise. Either the cancers would have grown very slowly or not at all and never caused symptoms, or women would have died from something else before their breast cancer was diagnosed.