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For years, GreenMedInfo has been reporting on the overdiagnosis of cancer. Cancer overdiagnosis is one of the most serious and dangerous problems in medicine today. The over diagnosed cancer poses no threat. But the unnecessary chemotherapy and radiation, while offering no help, do pose the significant threat of stress, discomfort, illness and even possibly causing real cancers.
As that earlier reporting made clear, most studies indicate that cancer screening does not reduce the risk of dying from the cancer it is screening for (1). But it does introduce the risk of the harms caused by screening, false positives and overdiagnosis.
Perhaps the most serious story of overdiagnosis is thyroid cancer. For women, the risk of thyroid cancer overdiagnosis ranges from 50% to as high as 70-80% in the U.S., France, Italy and Australia. For men, the fear is not much lessened with overdiagnosis climbing to 45% in the U.S. and as high as 70% in some other countries (2).
Breast cancer is an almost equally terrifying concern. A systematic review of the research found that the risk of overdiagnosis of breast cancer is an incredible 52% (3). More recent research shows no improvement. In fact, the picture is getting worse. A 2014 study published in the Journal of the American Medical Association showed that ten years or more of regular mammograms leads to a false positive in over 60% of women (4).
Men face similar problems with prostate cancer. Though PSA screening for prostate cancer provides no benefit, since it does not reduce the rate of death, it does result in false positives in 12-13% of men who undergo the test three to four times (5).
The New Evidence
And now, powerful new evidence adds to the weight and seriousness of the dangerous problem of cancer overdiagnosis. The new evidence comes from an important new Australian study that looked at the risk of overdiagnosis in five cancers: prostate, breast, kidney, thyroid and melanoma. The authors declared the results to be "a substantial problem that urgently requires changes in public health policy."
The new study defines overdiagnosis as "the diagnosis of cancer in people who would never have experienced symptoms or harm had the cancer remained undetected and untreated."
For women, the new study found overdiagnosis risks for thyroid cancer in the same range as the earlier studies. 73% of thyroid cancers were actually overdiagnosis.
Earlier research has shown that the problem with thyroid cancer comes from the twin problems of overdiagnosis and over definition. One of the most common kinds of thyroid cancer turns out not to be cancer at all. Encapsulated Follicular Variant of Papillary Thyroid Cancer accounts for about one in every 6.5 people diagnosed with thyroid cancer each year in the U.S. But that common form of thyroid cancer is now known not to be a cancer at all. So, all those people received unnecessary and harmful radiation because of overdiagnosis due to over definition (6).
For breast cancer, the new study found an overdiagnosis rate of 22%. A shocking 58% of all kidney cancers were actually overdiagnosis. The rate of overdiagnosis for melanomas was an almost as bad 54%. Overall, 18% of all cancer diagnoses for women were over diagnosed.
For men, the numbers are just as alarming. Thyroid cancer, again, tops the list at a 73% rate of overdiagnosis. 42% of all prostate cancer diagnoses are actually overdiagnoses. The number for kidney cancers is also 42%. And overdiagnosis of melanomas comes in at 58%. Overall for men, 24% of all cancer diagnoses are overdiagnoses.
The overdiagnosis of cancer in people who never would have experienced symptoms or harm that leads to treatments that do cause symptoms and harm is one of the most serious problems in medicine today.
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1. Saquib N, Saquib J, Ioannidis JP. Does screening for disease save lives in asymptomatic adults? Systematic review of meta-analyses and randomized trials. Int J Epidemiol 2015;44:264-77.
2. Vaccarella S, Franceschi S, Bray F, et al. Worldwide Thyroid-Cancer Epidemic? The Increasing Impact of Overdiagnosis. NEJM 2016;375:614-7.
3. Jørgensen KJ, Gøtzsche PC. Overdiagnosis in publicly organised mammography screening programmes: systematic review of incidence trends. BMJ 2009;339:b2587.
4. Pace LE, Keating NL. A systematic assessment of benefits and risks to guide breast cancer screening decisions. JAMA 2014;311:1327-35.
5. Chou R, Croswell JM, Dana T, et al. Screening for prostate cancer: a review of the evidence for the US Preventive Services Task Force. Ann Intern Med 2011;155:762-71.
6. Yuri E. Nikiforov, Raja R. Seethala, Giovanni Tallini, et al. A Paradigm Shift to Reduce Overtreatment of Indolent Tumors. JAMA Oncol 2016;2(8):1023-1029.