Estimates of overdiagnosis of invasive breast cancer associated with screening mammography

School of Public Health, University of Sydney, Sydney, NSW, Australia.
Cancer Causes and Control (Impact Factor: 2.74). 11/2009; 21(2):275-82. DOI: 10.1007/s10552-009-9459-z
Source: PubMed


To estimate the extent of overdiagnosis of invasive breast cancer associated with screening in New South Wales, Australia, a population with a well-established mammography screening program which has achieved full geographic coverage.
We calculated overdiagnosis as the observed annual incidence of invasive breast cancer in NSW in 1999-2001 (a screened population) minus the expected annual incidence in this population at the same time, as a percentage of the expected incidence. We estimated expected incidence without screening in 1999-2001 from the incidence of invasive breast cancer in: (1) women in unscreened age groups (interpolation method); and (2) women in all age groups prior to the implementation of screening (extrapolation method). We then adjusted these estimates for trends in major risk factors for breast cancer that may have coincided with the introduction of mammography screening: increasing obesity, use of hormone replacement therapy (HRT) and nulliparity. Finally, we adjusted for lead time to produce estimates of expected incidence in 1999-2001. These were compared with the observed incidence in 1999-2001 to calculate overdiagnosis of breast cancer associated with screening.
Overdiagnosis of invasive breast cancer among 50-69 year NSW women was estimated to be 42 and 30% using the interpolation and extrapolation methods, respectively.
Overdiagnosis of invasive breast cancer attributable to mammography screening appears to be substantial. Our estimates are similar to recent estimates from other screening programmes. Overdiagnosis merits greater attention in research and in clinical and public health policy making.

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    • "Other research has shown that even a significant proportion of invasive breast tumours identified by screening are not life-threatening and disappear if left untreated [28]. This means that up to 40% of tumours identified by breast cancer screening are not life-threatening and provide an artificial increase in incidence [28] [29] – and also a false increase in survival. Fox, mentioned above [6], plotted the change in incidence of breast cancer from the 1930s to the mid 1970s and compared this curve with that of breast cancer mortality over the same period. "
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    ABSTRACT: Cancer treatment will be effective only if it is be based on a valid paradigm of what cancer is and therefore capable of affecting the course of the disease. A review in 1993 found no evidence that surgery affected the course of the disease and an alternative paradigm was proposed. A review of mammography screening trials in 1996 found no benefits from breast cancer screening. This was predicted by this alternative paradigm. This review updates the evidence twenty years later. To identify evidence that the primary treatment of cancer, surgery, has been shown to affect the course of the disease. If there is no such evidence, then to identify the correct paradigm of what cancer is from other cancer treatments that have been shown to be effective. Because surgery has never been shown in a randomised controlled trial to affect the course of cancer seven other indirect methods were used to evaluate its efficacy. None of the seven indirect methods used showed that surgery clearly affects the course of the disease for any type of cancer. The lack of benefits from cancer screening now includes not only from breast cancer but also from bowel, lung, prostate and ovarian cancer screening. This confirms that cancer surgery is based on an invalid paradigm of what cancer is. Survival figures following treatments based on an alternative paradigm that assumes cancer is a systemic disease were found to be superior to those following surgery, reinforcing the conclusion that cancer is a systemic disease and that cancer surgery is unlikely to be of benefit in most cases. No benefits can be expected to be achieved from using cancer surgery except in a few immediately life-threatening situations. Surgery appears to be based on an invalid paradigm of what cancer is. Cancer appears to be a systemic disease and therefore standard treatments need to be reassessed in this light.
    Medical Hypotheses 01/2014; 82(4). DOI:10.1016/j.mehy.2014.01.004 · 1.07 Impact Factor
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    • "Some of the increased incidence is related to life-style issues such as the use of hormone replacement therapy and obesity, but the most dramatic increase in incidence coincided with the commencement of the BreastScreen Australia Program.1 Estimates of the rate of overdiagnosis vary and are dependent on models used to estimate overdiagnosis.22 It has been estimated that in NSW, there is a 30% overdiagnosis rate after adjustments for underlying breast cancer risk and lead time bias,23 a rate similar to that predicted by analysis of other screening programmes.24 In contrast, a recent literature review of overdiagnosis in European screening programmes found that the overdiagnosis rate varied between 1% and 10% after adjustment for the underlying breast cancer risk and lead time bias.22 "
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    ABSTRACT: In 2011, BreastScreen Australia celebrated 20 years of mammographic screening for breast cancer in Australia. There has been a reduction in mortality from breast cancer over the last two decades, coincident with mammographic screening. However, there are concerns that mammographic screening may result in overdiagnosis of breast cancer and that the reduction in mortality from breast cancer is the result of better treatment rather than screening. This article reviews the evidence on which mammographic screening for breast cancer is based, considers the issue of overdiagnosis of breast cancer by screening mammography, and assesses the role of screening mammography in the reduction in breast cancer mortality seen over the last two decades.
    03/2013; 60(1). DOI:10.1002/jmrs.6
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    • "In service screening, in fact, a control group is not available since the entire target population is invited to be screened. In most studies the method used to overcome this problem is to estimate the incidence or mortality expected in the absence of screening, modelling the incidence or mortality rates observed before the start of the screening program [24,26-29]. However, the estimate of expected rates is subject to a strong statistical uncertainty and it strongly influences the estimate of the final outcome (mortality reduction or overdiagnosis). "
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    ABSTRACT: The use of screening mammography is still under debate within the medical community. The aim of this study is to define a balance sheet of benefits (breast cancer mortality reduction) and harms (overdiagnosis) for mammography screening programs. We compared breast cancer incidence and mortality in two cohorts of women, defined as 'attenders' or 'non-attenders' on the basis of the individual attitudes towards screening, who were invited to the first round of the Florentine screening program. The effects of screening exposure on breast cancer incidence and mortality were evaluated by fitting Poisson regression models adjusted for age at entry, marital status and deprivation index. We performed a sensitivity analysis excluding 34 women not responding to the invitation with a breast cancer diagnosis in the following six months. In total, we included 51,096 women aged 50 to 69 years invited at the first screening round (1991 to 1993) and followed-up for breast cancer incidence and mortality until 31 December 2007 and 31 December 2008, respectively The estimate of mortality reduction varies from 45% among 50 to 59 year-old women up to 51% among 60 to 69 year-old women. The estimate of overdiagnosis, according to the cumulative-incidence method, is an additional 10% of all breast cancer cases among 60 to 69 year-old women screened. Comparing the breast cancer mortality and breast cancer incidence between attenders and non-attenders, we have determined that the overall cost to save one life corresponds to no more than one over-diagnosed tumor (from 0.6 to 1 depending on the selection criteria of the cohort), even if a residual self-selection bias cannot be excluded.
    Breast cancer research: BCR 01/2012; 14(1):R9. DOI:10.1186/bcr3090 · 5.49 Impact Factor
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