Time for your mammogram? PSA? Thinking about doing the ultrasound heart screening you saw advertised? Isn't screening always a Mom and God and apple pie proposition? The scientific answer, in spite of tradition, financial interests and legal fears, is NO! All screening tests in medicine have downsides and often some very significant ones.A negative aspect of screening that has started to show itself with mammography in the last 10 years is called over-diagnosis. How can you have over-diagnosis of a cancer? A breast cancer diagnosis is made - a biopsy, the pathologist sees malignant cells under the microscope, surgery, radiation and/or chemotherapy follow. The patient is over-diagnosed when her cancer, if gone undetected, would never in her entire life cause any ill effect.How can a "patient" have a cancer that would not result in bad things happening? Some of these tumors outgrow their blood supply and die. With some tumors, the body's defense mechanisms block the growth of the tumor and do not allow it to enlarge. Finally, other tumors simply grow so slowly that they never get big enough to be felt or hurt or cause any difficulty.The patient is over-diagnosed (the tumor never needed to be discovered) and over-treated with all the emotion, pain and financial trauma that accompanies a cancer diagnosis.A recent New England Journal of Medicine study confirms what a dozen trials over the last decade have shown, that 31% of women, diagnosed with breast cancer by mammography in the last 30 years have been over-diagnosed and over-treated. The authors estimated that in 2008 alone, 70,000 American women were over-diagnosed with breast cancer.The difficulty is that although we can substantiate that in a group of women that over-diagnosis has occurred, we lack the technology to sort out which individual woman is over-diagnosed. And when a patient is over-diagnosed, the therapy that follows can have no benefit, only harm.This is not a call to quit doing screening mammography. Screening mammography does save lives, but at a huge cost in terms of false positives, biopsies, over-diagnosis and over-treatment. Every woman should have the facts regarding both the RISKS and benefits of screening and then make the decision that is best for her.Dr. Mohler has practiced family medicine in Grand Junction for 38 years. He has a particular interest in pharmaceutical education. Phil works part-time for both Primary Care Partners and Rocky Mountain Health Plans.