Modelling the overdiagnosis of breast cancer due to mammography screening in women
aged 40 to 49 in the United Kingdom |
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Authors: | Necdet B Gunsoy Montserrat Garcia-Closas Sue M Moss |
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Institution: | 1.Division of Genetics and Epidemiology, Institute of Cancer Research, 15 Cotswold Road, Sutton, SM2 5NG, UK;2.Breakthrough Breast Cancer Centre, Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK;3.Centre for Cancer Prevention, Queen Mary University of London, Wolfson Institute of Preventive Medicine, Charterhouse Square, London, EC1M 6BQ, UK |
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Abstract: | IntroductionOverdiagnosis of breast cancer due to mammography screening, defined as the
diagnosis of screen-detected cancers that would not have presented clinically in a
women''s lifetime in the absence of screening, has emerged as a highly contentious
issue, as harm caused may question the benefit of mammographic screening. Most
studies included women over 50 years old and little information is available for
younger women.MethodsWe estimated the overdiagnosis of breast cancer due to screening in women aged 40
to 49 years using data from a randomised trial of annual mammographic screening
starting at age 40 conducted in the UK. A six-state Markov model was constructed
to estimate the sensitivity of mammography for invasive and in situ breast cancer and the screen-detectable mean sojourn time for
non-progressive in situ, progressive in situ, and invasive
breast cancer. Then, a 10-state simulation model of cancer progression, screening,
and death, was developed to estimate overdiagnosis attributable to screening.ResultsThe sensitivity of mammography for invasive and in situ breast cancers
was 90% (95% CI, 72 to 99) and 82% (43 to 99), respectively. The screen-detectable
mean sojourn time of preclinical non-progressive and progressive in situ
cancers was 1.3 (0.4 to 3.4) and 0.11 (0.05 to 0.19) years, respectively, and
0.8 years (0.6 to 1.2) for preclinical invasive breast cancer. The proportion of
screen-detected in situ cancers that were non-progressive was 55% (25 to
77) for the first and 40% (22 to 60) for subsequent screens. In our main analysis,
overdiagnosis was estimated as 0.7% of screen-detected cancers. A sensitivity
analysis, covering a wide range of alternative scenarios, yielded a range of 0.5%
to 2.9%.ConclusionAlthough a high proportion of screen-detected in situ cancers were
non-progressive, a majority of these would have presented clinically in the
absence of screening. The extent of overdiagnosis due to screening in women aged
40 to 49 was small. Results also suggest annual screening is most suitable for
women aged 40 to 49 in the United Kingdom due to short cancer sojourn times. |
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