A large, long-term study of the value of screening mammography for saving lives of women from breast cancer supports previous studies: there was no detectable benefit in terms of lives saved thanks to routine use of the technology. The study appeared in BMJ.
The study authors led by Dr. Anthony B. Miller of the Dalla Lana School of Public Health, University of Toronto, Canada, followed almost 90,,000 women participants in the Canadian National Breast Screening Study, aged 40 to 59, beginning in 1980. While there are many different slices and dices of the voluminous Study dataset in the article, the sum and substance of it is: within the range of statistical error, there were no additional lives saved from mammography screening as compared with no screening, period. Worse, given the number of cases of breast cancer thanks to the fallacy called overdiagnosis, many women (perhaps 22 percent) were subjected to procedures including biopsies and surgeries and complications thereof, which were done to save them from non-threatening lesions. And of course just about everyone who has a mammogram undergoes some degree of mental and emotional turmoil.
While various parsings of the data seemed to show some advantage in terms of length of time of survival for women diagnosed via screening as compared to those whose cancers were detected by physical exam or symptoms, deeper more thorough analysis showed that to be a fallacy, an apparent but not real benefit due to certain well-known epidemiological mirages or bias. Lead-time bias is one such, where the apparent survival duration after mammographic diagnosis is longer than the time after exam-detected cancer. But the actual life expectancy does not change in reality only the length of time that the cancer was known to be present. As mentioned above, overdiagnosis is another nuanced confounder: cancers detected and removed that would never have come to the attention of anyone without the mammogram.
The issue of when to start screening and how often, at what ages, has been debated for decades. A blockbuster report from a Federal panel in 2009 advised women, after reviewing all the available studies, to pass on mammograms entirely before age 50, and then get one only every other year until age 75. We discussed several subsequent studies which came to the same conclusions, earlier this year.
An editorial in the same journal noted these possible limitations of the study: The rate of overdiagnosis did not include ductal carcinoma in situ, and the trial provides no data for women older than 60.
ACSH s Dr. Gil Ross had this comment: The study s authors advised that, the rationale for screening by mammography be urgently reassessed by policy makers. I echo that sentiment. But it must be emphasized that this advisory is only regarding routine screenings NOTHING to do with women who feel a lump, have a past history of breast diseases, or the BRCA gene.
"That being said, I strongly believe we ve had enough scientific study on this subject, from both sides of the Atlantic and elsewhere, and that the conclusion is obvious: routine screening mammography does more harm than good. This situation is quite analogous to prostate cancer screening: Just say no!
