title: Evaluation of health benefits and harms of the breast cancer screening programme in the Basque Country using discrete event simulation.
abstract: BACKGROUND
  Since the breast cancer screening programme in the Basque Country (BCSPBC) was started in 1996, more than 400,000 women aged 50 to 69 years have been invited to participate. Based on epidemiological observations and simulation techniques it is possible to extend observed short term data into anticipated long term results. The aim of this study was to assess the effectiveness of the programme through 2011 by quantifying the outcomes in breast cancer mortality, life-years gained, false positive results, and overdiagnosis.
  
  
  METHODS
  A discrete event simulation model was constructed to reproduce the natural history of breast cancer (disease-free, pre-clinical, symptomatic, and disease-specific death) and the actual observed characteristics of the screening programme during the evaluated period in the Basque women population. Goodness-of-fit statistics were applied for model validation. The screening effects were measured as differences in benefits and harms between the screened and unscreened populations. Breast cancer mortality reduction and life-years gained were considered as screening benefits, whereas, overdiagnosis and false positive results were assessed as harms. Results for a single cohort were also obtained.
  
  
  RESULTS
  The screening programme yielded a 16 % reduction in breast cancer mortality and a 10 % increase in the incidence of breast cancer through 2011. Almost 2 % of all the women in the programme had a false positive result during the evaluation period. When a single cohort was analysed, the number of deaths decreased by 13 %, and 4 % of screen-detected cancers were overdiagnosed. Each woman with BC detected by the screening programme gained 2.5 life years due to early detection corrected by lead time.
  
  
  CONCLUSIONS
  Fifteen years after the screening programme started, this study supports an important decrease in breast cancer mortality due to the screening programme, with reasonable risk of overdiagnosis and false positive results, and sustains the continuation of the breast cancer screening programme in the Basque population.
authors.affiliation: Gipuzkoa AP-OSI Research Unit, Integrated Health Organization Alto Deba, Avda Navarra 16, 20500, Arrasate-Mondragón, Gipuzkoa, Spain. arantzazu.arrospideelgarresta@osakidetza.net.|Public Health Division of Gipuzkoa, BIODONOSTIA Research Institute, Paseo Dr Beguiristain s/n, 20014, Donostia, Gipuzkoa, Spain. arantzazu.arrospideelgarresta@osakidetza.net.|REDISSEC (Red de Investigación en Servicios de Salud en Enfermedades Crónicas - Spanish Health Services Research on Chronic Patients Network), Bilbao, Spain. arantzazu.arrospideelgarresta@osakidetza.net.
authors.forename: Arantzazu
authors.initials: A
authors.lastname: Arrospide
authors.affiliation: REDISSEC (Red de Investigación en Servicios de Salud en Enfermedades Crónicas - Spanish Health Services Research on Chronic Patients Network), Bilbao, Spain. montse.rue@cmb.udl.cat.|Basic Medical Sciences department, Biomedical Research Institute of Lleida, University of Lleida, Avda. Rovira Roure 80, 25198, Lleida, Spain. montse.rue@cmb.udl.cat.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Rue
authors.affiliation: Department of Public Health, Erasmus University Medical Center Rotterdam, Dr Molewaterplein 50, 3015 GE, Rotterdam, The Netherlands. n.vanravesteyn@erasmusmc.nl.
authors.forename: Nicolien T
authors.initials: NT
authors.lastname: van Ravesteyn
authors.affiliation: REDISSEC (Red de Investigación en Servicios de Salud en Enfermedades Crónicas - Spanish Health Services Research on Chronic Patients Network), Bilbao, Spain. MComas@imas.imim.es.|Evaluation and Epidemiology Department, Hospital del Mar - IMIM (Hospital del Mar Medical Research Institute), Passeig Maritim 25-29, 08003, Barcelona, Spain. MComas@imas.imim.es.
authors.forename: Merce
authors.initials: M
authors.lastname: Comas
authors.affiliation: Public Health Division of Gipuzkoa, BIODONOSTIA Research Institute, Paseo Dr Beguiristain s/n, 20014, Donostia, Gipuzkoa, Spain. epidem3-san@ej-gv.es.|CIBER of Epidemiology and Public Heath, C/Monforte de Lemos 3-5, 28029, Madrid, Spain. epidem3-san@ej-gv.es.
authors.forename: Nerea
authors.initials: N
authors.lastname: Larrañaga
authors.affiliation: Breast Cancer Early Detection Programme, Public Health Division of Bizkaia, Basque Government, Alameda Rekalde 39, 48008, Bilbao, Bizkaia, Spain. garbine.sarriugarteirigoien@osakidetza.net.
authors.forename: Garbiñe
authors.initials: G
authors.lastname: Sarriugarte
authors.affiliation: Gipuzkoa AP-OSI Research Unit, Integrated Health Organization Alto Deba, Avda Navarra 16, 20500, Arrasate-Mondragón, Gipuzkoa, Spain. javier.marmedina@osakidetza.net.|Public Health Division of Gipuzkoa, BIODONOSTIA Research Institute, Paseo Dr Beguiristain s/n, 20014, Donostia, Gipuzkoa, Spain. javier.marmedina@osakidetza.net.|REDISSEC (Red de Investigación en Servicios de Salud en Enfermedades Crónicas - Spanish Health Services Research on Chronic Patients Network), Bilbao, Spain. javier.marmedina@osakidetza.net.|Health Management Service, Integrated Health Organization Alto Deba, Avda Navarra 16, 20500, Arrasate-Mondragón, Gipuzkoa, Spain. javier.marmedina@osakidetza.net.
authors.forename: Javier
authors.initials: J
authors.lastname: Mar
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology*; D005260:Female; D006801:Humans; D015994:Incidence; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D009026:Mortality; D012042:Registries; D018570:Risk Assessment