"If mass mammography screening for breast cancer worked well fewer women would die from the disease. And yet a new study published in JAMA Internal Medicine httparchinte.jamanetwork.comarticle.aspxdoi.jamainternmed.. has found something that may seem counterintuitive More breast cancer screening didnt actually save lives. Screening did however lead to more overdiagnosis detecting cancers that would not have been fatal or even harmful. Related The problem with Taylor Swifts advice about cancer screening http  The research led by Richard Wilson of Harvard University revealed that in more than  US counties mammography screening programs were linked with more diagnoses of smaller breast cancers  but not with fewer deaths or with fewer larger breast cancers which theoretically would be prevented by finding the disease early through screening. You can see this clearly in the chart below The number of diagnosed breast cancers rose with more screening yet the number of deaths from breast cancer  years later remained stubbornly stable.  Extent of screening breast cancer incidence and mortality in women  years and older in  US counties. JAMA Internal Medicine httparchinte.jamanetwork.comarticle.aspxdoi.jamainternmed.. To be clear Mass screening is different from using technologies like ultrasounds to diagnose people at risk of a disease or who have symptoms that require investigation. And not all mass screening programs are bad. Colorectal cancer screening for example has been shown to save lives as a result of early detection and the Pap test transformed cervical cancer into a treatable disease.  But this isnt the first study to call into question the benefits of mammography and whether women are too often the victims of overdiagnosis.   The trouble with overdiagnosis is that while the cancers doctors find wouldnt have harmed their patients the treatment and stress that result from the diagnosis probably will. We have to find a better way to screen women for breast cancer  Overdiagnosis in thyroid cancer While the incidence of the disease increased after a screening program was instituted in South Korea the thyroid cancer mortality rate stayed the same. New England Journal of Medicine http The medical community has known http about overdiagnosis and overtreatment for years documenting the problem in a range of cancers  in breast prostate lung and thyroid http which you can see in the chart above. This raises a tough question What should the medical community do about overdiagnosis In a related commentary httparchinte.jamanetwork.comarticle.aspxdoi.jamainternmed.. in the journal a pair of doctors from the University of Washington School of Medicine note that the estimates of overdiagnosis of breast cancer are frustratingly broad  from less than  percent to  percent or more of women who get screened. In other words we dont actually know how bad the problem is. Sadly they write we are left in a conundrum. Women will increasingly approach their physicians with questions and concerns about overdiagnosis and we have no clear answers to provide. The authors of the newest study dont advocate no screening. Instead they note that the benefits of screening will probably be more favorable when screening is directed at people with a high risk of the disease  such as those with a family history of breast cancer.  The US Preventive Services Task Force httpscreeningforbreastcancer.org which analyzes the best available evidence to create guidelines for doctors now recommends biennial mammography screening for the general population in women ages  to . For women under  and over   who arent at a high risk of breast cancer  the benefits of mass screening are less clear. There are small things doctors can do that still dont happen often enough. For example most women arent told about the potential downsides of mammography screening  even though theyre almost always briefed on the benefits. How to think about the benefits and harms of mammography. Harding Center for Risk Literacy Harding Center for Risk Literacy https  For now its up to patients to talk to their doctors about their particular risk profiles and how to screen accordingly. We also need to remember that in medicine more often than not we generally overestimate the benefits and underestimate the harms http"