The over-emphasis on the importance of screening, despite a lack of strong evidence, has been elevated to such a degree that some even equate screening with prevention of breast cancer. The National Breast Cancer Coalition hopes that today’s release of the US Preventive Services Task Force (USPSTF) revised recommendations will put the brakes on this run-away train and will put screening and its limitations into proper perspective.
This means that for every 2000 women invited for screening throughout 10 years, one will have her life prolonged. In addition, 10 healthy women, who would not have been diagnosed if there had not been screening, will be diagnosed as breast cancer patients and will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress for many months because of false positive findings.It's one thing to know that there is a risk of false positives in the abstract; it's another to see the numbers are quite that stark in terms of number of women undergoing unnecessary treatment for every life saved.
The White Hat: "Let's talk about that unnecessary burden for a bit. An abnormal BSE will likely result in a clinic visit, which may then lead to a clinical breast exam (CBE), a mammogram, or a needle-biopsy. All of these procedures require time and money, and may also cause a certain amount of anxiety. Let's forget those for the moment and talk instead about actual physical harm caused by an unnecessary test. CBE is mostly harmless, as are mammograms if you factor out the low dose of radiation. Needle biopsies, however, can cause "hematomas, infection, and scarring; from wire localization itself, complications include vasovagal reactions (7 percent) and, rarely, prolonged bleeding (1 percent) and extreme pain (1 percent)"These numbers were pulled from a packet (pdf) given at a 1997 NIH Symposium. So yes, you can quantify the physical harm. As for the psychological distress, RTFA-- the Cochran report cites eight studies (Brewer, Bulow, Brodersen 2006 & '7, Barton, Brett, Lerman, and Gram) that all found some amount of psychological distress associated with false positive results. If you want a quantifiable number, you might look at it from a financial perspective-- Barton ('01) found that women who have had false positive see their doctors more often, which means that they're paying for excess treatment based on unsound reasoning brought about by a false positive.
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posted by The White Hat at 11:27 AM on November 17, 2009 [2 favorites]