Screening Mammography: Making Well Women Sick

                In December 2009, the U.S. Preventive Services Task Force recommended that women between the ages of 50 and 74 be screened for breast cancer once every two years rather than once every year.  It also recommended against routine screening of women younger than 50 and older than 74.

                Almost immediately after the recommendations were made public, there was a large outcry against them.  I was surprised that so many people were able to decide so quickly that the recommendations were wrong.  To me it seemed there hadn’t been enough time to learn about and evaluate the evidence upon which the Task Force based its recommendations.  Since women and their doctors are now in the midst of making decisions about when and how frequently women should be screened and because I don’t want women to make uninformed decisions about their health care, I decided to devote this and the next couple of postings to providing the information I think they will need.

                 The U.S. Preventive Services Task Force is a panel made up of primary care providers (e.g., internists, pediatricians, family physicians, gynecologists/obstetricians, nurses, and health care specialists) who are not only experts in prevention but also experts in understanding and interpreting evidence-based medicine.  In the case of breast screening that would include scientific results important for evaluating how effective screening mammography is.  The members of the panel are independent; they are not part of the Federal government.  Plus, financial cost is not taken into consideration; it plays no part in determining the panel’s recommendations.  But human cost does.

                The Task Force will not recommend a service such as mammography screening unless its benefits outweigh its harms.  Just being able to identify breast cancer in women is not good enough.  Why? Because of the tens of thousands of women who are screened for breast cancer every year the vast majority are well.  And although we tend to evaluate doctors in terms of how good they are at making people who are sick well, it’s just as important to keep in mind that they’re also not supposed to make people who are well sick. So the questions boil down to these: What are the harms of screening women younger than 50 and older than 74? What are the harms of screening once a year? How do they occur? And how do they outweigh the benefits?

                The harms of screening mammography come from two sources: (1) incorrect diagnoses by radiologists reading and interpreting mammograms and (2) the inadequacy and carcinogenic properties of the mammography technology itself.  My next postings will cover how incorrect diagnoses occur, the steps radiologists take to reduce the number of incorrect diagnoses, whether adding computer-aided-detection to mammography reduces the risk of incorrect diagnoses, the harms associated with incorrect diagnoses, and the steps women can take to reduce their risk of being incorrectly diagnosed.