Overdiagnosis associated with breast cancer screening: A simulation study to compare lead-time adjustment methods.
OBJECTIVE
Estimating overdiagnosis associated with breast cancer screening may use annual incidence rates of cancer. We simulated populations invited to screening programmes to assess two lead-time adjustment methods.


METHODS
Overdiagnosis estimates were computed using the compensatory drop method, which considered the decrease in incidence of cancers among older age groups no longer offered screening, and the method based on the decrease in incidence of late-stage cancers.


RESULTS
The true value of overdiagnosis was 0% in all the data sets simulated. The compensatory drop method yielded an overdiagnosis estimate of -0.1% (95% credibility interval -0.5% to 0.5%) when participation rates among the population and risk of cancers were constant. However, if participation rates increased with calendar year as well as risk of cancer with birth cohorts, the overdiagnosis estimated was 11.0% (10.5-11.6%). Using the method based on the incidence of early- and late-stage cancers, overdiagnosis estimates were 8.9% (8.5-9.3%) and 17.6% (17.4-17.9%) when participation rates and risks of cancer were constant or increased with time, respectively.


CONCLUSIONS
Adjustment for lead time based on the compensatory drop method is accurate only when participation rates and risks of cancer remain constant, whereas the adjustment method based on the incidence of early- and late-stage cancers results in overestimating overdiagnosis regardless of stability of participation rates and breast cancer risk.
Unité d'évaluation médicale, Pavillon Taillefer, Centre Hospitalier Universitaire de Grenoble, Cs 10217, 38043 Grenoble Cedex 9, France; Université Joseph Fourier Grenoble 1, Techniques de l'Ingénierie Médicale et de la Complexité - Informatique Mathématiques et Applications Grenoble, Unité Mixte de Recherche 5525, 38041 Grenoble, France. Electronic address: aseigneurin@chu-grenoble.fr.
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Seigneurin
Unité d'évaluation médicale, Pavillon Taillefer, Centre Hospitalier Universitaire de Grenoble, Cs 10217, 38043 Grenoble Cedex 9, France; Université Joseph Fourier Grenoble 1, Techniques de l'Ingénierie Médicale et de la Complexité - Informatique Mathématiques et Applications Grenoble, Unité Mixte de Recherche 5525, 38041 Grenoble, France.
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Labarère
Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary University of London, Charterhouse Square, London EC1 M 6BQ, UK.
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Duffy
Registre du Cancer de l'Isère, Pavillon E, Centre Hospitalier Universitaire de Grenoble, Cs 10217, 38043 Grenoble Cedex 9, France.
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Colonna
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D055088:Early Detection of Cancer / Q000379:methods; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography / Q000379:methods*; D000069342:Medical Overuse / Q000706:statistics & numerical data*; D008875:Middle Aged
Breast neoplasms; Incidence; Lead time; Mass screening; Overdiagnosis; Simulation study