title: Estimate of Opportunistic Prostate Specific Antigen Testing in the Finnish Randomized Study of Screening for Prostate Cancer.
abstract: Screening for prostate cancer remains controversial, although ERSPC (European Randomized Study of Screening for Prostate Cancer) showed a 21% relative reduction in prostate cancer mortality. The Finnish Randomized Study of Screening for Prostate Cancer, which is the largest component of ERSPC, demonstrated a statistically nonsignificant 16% mortality benefit in a separate analysis. The purpose of this study was to estimate the degree of contamination in the control arm of the Finnish trial.
  
  
  
  Altogether 48,295 and 31,872 men were randomized to the control and screening arms, respectively. The screening period was 1996 to 2007. The extent of prostate specific antigen testing was analyzed retrospectively using laboratory databases. The incidence of T1c prostate cancer (impalpable prostate cancer detected by elevated prostate specific antigen) was determined from the national Finnish Cancer Registry.
  
  
  
  Approximately 1.4% of men had undergone prostate specific antigen testing 1 to 3 years before randomization. By the first 4, 8 and 12 years of followup 18.1%, 47.7% and 62.7% of men in the control arm had undergone prostate specific antigen testing at least once and in the screening arm the proportions were 69.8%, 81.1% and 85.2%, respectively. The cumulative incidence of T1c prostate cancer was 6.1% in the screening arm and 4.5% in the control arm (RR 1.21, 95% CI 1.13-1.30).
  
  
  
  A large proportion of men in the control arm had undergone a prostate specific antigen test during the 15-year followup. Contamination is likely to dilute differences in prostate cancer mortality between the arms in the Finnish screening trial.
authors.affiliation: Department of Urology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland. Electronic address: tuomas.kilpelainen@hus.fi.
authors.forename: Tuomas P
authors.initials: TP
authors.lastname: Kilpeläinen
authors.affiliation: Department of Urology, Kanta-Häme Central Hospital, Hämeenlinna, Finland.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Pogodin-Hannolainen
authors.affiliation: School of Health Sciences, University of Tampere, Tampere, Finland.
authors.forename: Kimmo
authors.initials: K
authors.lastname: Kemppainen
authors.affiliation: Finnish Cancer Registry, Helsinki, Finland.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Talala
authors.affiliation: School of Health Sciences, University of Tampere, Tampere, Finland; UKK Institute for Health Promotion Research, Tampere, Finland.
authors.forename: Jani
authors.initials: J
authors.lastname: Raitanen
authors.affiliation: Department of Urology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: Kimmo
authors.initials: K
authors.lastname: Taari
authors.affiliation: Fimlab Laboratories, Department of Pathology, Tampere University Hospital, Tampere, Finland.
authors.forename: Paula
authors.initials: P
authors.lastname: Kujala
authors.affiliation: Department of Urology, University of Tampere, Tampere University Hospital, Tampere, Finland; Department of Urology, Tampere University Hospital, Tampere, Finland.
authors.forename: Teuvo L J
authors.initials: TLJ
authors.lastname: Tammela
authors.affiliation: School of Health Sciences, University of Tampere, Tampere, Finland.
authors.forename: Anssi
authors.initials: A
authors.lastname: Auvinen
mesh_terms: D000368:Aged; D055088:Early Detection of Cancer; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood*; D015203:Reproducibility of Results; D012189:Retrospective Studies
chemical_list: D017430:Prostate-Specific Antigen
keywords: bias; mass screening; mortality; prostate-specific antigen; prostatic neoplasms