Might have otherwise gone undetected because the

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might have otherwise gone undetected because the cancers were benign or because women died before the cancer could progress to the point of being detected by older technology. Only about 3 in every 100 women will die of breast cancer by age 85, a substantial number, but considerably smaller than the oft-quoted 1 in 9. d) No organization currently recommends mammograms for women before age 40. Results of ten randomized clinical trials – a summary a) There is no evidence that screening asymptomatic women in their 40s reduces the mortality from breast cancer, or that biennial screening is less effective than annual screening. Despite the absence of any proven benefit from an aggressive screening protocol, the UVA health clinic, as well as a number of cancer organizations, continue to recommend that women obtain mammograms annually , beginning at age 40. b) For women over 50, the benefit of biennial screening is real, although still more modest than one might have been led to believe. Consider women who begin screening at age 50 and are screened every two years for twenty years. For every 270 women who undergo this procedure, one life is saved. Biennial screening of older women for the 20 years
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1 Gerd Gigerenzer, Calculated Risks , p. 41. .0072 + Mammogram (.90) - Mammogram (.10) Cancer (.008) .0008 No Cancer (.992) + Mammogram (.07) .06944 - Mammogram (.93) .92256 between ages 50 and 70 is the most cost-effective procedure, and even in this group, the cost is $21,000 per year of life saved . Annual exams, beginning at age 40, roughly triple the cost without increasing the benefit. While $21,000 per year of life saved is arguably worth paying, there are medical procedures with a more attractive cost/benefit ratio that are much less actively promoted than mammography screening. Also, the high cost clearly puts the procedure out of reach for much of the world’s population. False Positives. The following information pertains to the screening of asymptomatic women aged 40 to 50. It is presented here as a Bayes Law problem. 1 The probability that a women in this age group has breast cancer is 0.8 percent. If a woman has breast cancer, the probability is 90 percent she will have a positive mammogram.
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