title: Mammography benefit in the Canadian National Breast Screening Study-2: a model evaluation.
abstract: The CNBSS-2 among women aged 50-59 did not show any significant difference in breast cancer mortality between a control arm screened annually by CBE and a study arm screened by CBE and mammography. Because of this design, the benefit of screening compared to no screening could not be evaluated. We therefore conducted a modeling effort to estimate the benefit of mammography or CBE compared to no screening. We incorporated demographic, epidemiologic and screening characteristics of the CNBSS-2 in MISCAN. Stage-specific sensitivities of CBE, with and without mammography, and breast cancer incidence rate in the trial were estimated by comparing observed trial data with model predictions. We predicted the number of breast cancer deaths for both study arms of the CNBSS-2 and in the absence of screening, assuming improvement in prognosis by early detection. We estimated a 24-29% higher breast cancer incidence rate in the CNBSS-2 than the average Canadian rate. Estimated sensitivity of CBE (control arm) varied from 0.29 to 0.48 for stage T1c and from 0.6 to 0.65 for stage T2+. Estimated sensitivity of CBE supplemented with mammography (study arm) varied from 0.5 to 0.79 for stage T1c and was 0.95 for stage T2+. Expected breast cancer mortality reduction by annual CBE screening is 20.5% compared to no screening. Estimated breast cancer mortality reduction by mammography screening compared to no screening for the CNBSS-2 fell within the range 13.6-34.1%. Enrolled women had above average risk. Screening sensitivity in both arms was high. A benefit of mammography screening is supported by our modeling of the CNBSS-2 results.
authors.affiliation: Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands. a.rijnsburger@erasmusmc.nl
authors.forename: Adriana J
authors.initials: AJ
authors.lastname: Rijnsburger
authors.forename: Gerrit J
authors.initials: GJ
authors.lastname: van Oortmarssen
authors.forename: Rob
authors.initials: R
authors.lastname: Boer
authors.forename: Gerrit
authors.initials: G
authors.lastname: Draisma
authors.forename: Teresa
authors.initials: T
authors.lastname: To
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Miller
authors.forename: Harry J
authors.initials: HJ
authors.lastname: de Koning
mesh_terms: D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology*; D002170:Canada; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography / Q000379:methods*; D008403:Mass Screening; D008875:Middle Aged; D015233:Models, Statistical; D011379:Prognosis; D012680:Sensitivity and Specificity; D013997:Time Factors