When the Canadian study came along. Its sound bite was "No, it doesn't." In the field of cancer testing, no study has been so vigorously criticized. Before I say to you why, let me tell you what the Canadians did and what they found.
The Canadian National Breast Screening Study was the first of these trials to involve volunteers. All the women knew they were being studied and knew that they would be assigned to one of two groups by chance. This is important, because that is certainly plausible that these women were particularly motivated to find early breast cancers, so much so that they volunteered to be in the study a factor that might help explain the results. The study really had two components: one for younger women and one for older women.
Canada 1 randomized 50,000 women ages 40–49; one group received annual mammography and clinical breast exam, while the second received usual medical care. Canada 2 randomized 40,000 women ages 50–59, with one group receiving annual mammography and clinical breast exam, and the second receiving just the annual clinical breast exam.
So Canada 1 was testing the effect of clinical breast exam and mammography in women in their 40s, while Canada 2 was testing the effect of adding mammography to clinical breast exam in women in their 50s. After seven years, both studies showed that women who received mammography had no reduction in breast cancer mortality.
For screening proponents and mammographers, this finding was heretical and their reaction was swift: the study was roundly condemned. The critique boiled down to two major allegations: (1) the mammography groups included a higher%age of higher-risk women, making the comparisons unfair; and (2) the mammograms and those who read them were inadequate.
The unfair comparison criticism arose because it was alleged that as women entered the trial, study nurses directed women with a bad risk of breast cancer to the mammography group. Quite simply, the allegation was that the trial wasn't really randomized because women weren't assigned to groups solely by chance. The charge was taken very seriously, and Canada's National Cancer Institute ordered a review of the entire randomization process. Two years later, the independent review was published; no credible evidence of subversion was found. The heretical findings, therefore, could not be attributed to unfair comparison groups.
The allegation about inadequate mammography was twofold. First, the machines were said not to be "state of the art." Second, the radiologists or technologists were considered insufficiently trained. Inferior machines, inferior professional personnel . . . you may imagine, it was an American, not a Canadian, leading the charge. The charge was an odd one, however. The American study of mammography conducted 20 years earlier, the HIP, certainly didn't have modern-day mammograms, yet proponents were happy to argue that it demonstrated mammography worked. More important, there is little doubt that the Canadian mammograms did what they were supposed to, which was find small cancers.
More cancers were found in the women who received mammograms, and the cancers found were smaller than in control patients. In fact, the Canadian mammographers found more cancers and smaller cancers than did the mammographers in the Swedish studies.
Our website is not responsible for the information contained by this article. Webworldarticles.com is a free articles resource thus practically any visitor can submit an article. However if you notice any copyrighted material, please contact us and we will remove the article(s) in discussion right away.
This article was sent to us by:
Fiona Landman at
08152010
1. Understanding the Mesothelioma Cause
All articles in this directory are property of their respective authors. Additionally, read our Privacy Policy
© 2010 WebWorldarticles.com - All Rights Reserved. Partners: Gunblade Saga