title: Cancer overdiagnosis and overtreatment.
abstract: OBJECTIVE
  Overdiagnosis has become a major problem in medicine in general and cancer in particular. This is a summary of this problem.
  
  
  RESULTS
  Because of earlier detection, the nature of cancer has changed, from a disease usually diagnosed at a late and incurable stage to a heterogeneous condition that varies from clinically insignificant to rapidly aggressive. Screening programs for cancer have resulted in a dramatic increase in the diagnosis of clinically insignificant disease, balanced by improved survival and mortality because of significant cancers being diagnosed at a more curable stage. Overdiagnosis requires the presence of microfocal disease and a screening test to identify this. This exists for breast, prostate, and thyroid cancers, and to a lesser degree for renal and lung cancer. The problem of cancer overdiagnosis and overtreatment is complex, with numerous causes and many trade-offs. It is particularly important in prostate cancer, but is a major issue in many other cancer sites. Screening for prostate cancer appears, based on the best data from randomized trials, to significantly reduce cancer mortality.
  
  
  CONCLUSIONS
  Reducing overtreatment in patients diagnosed with indolent disease is critical to the success of screening.
authors.affiliation: Division of Urology, University of Toronto, Toranto, Ontario, Canada. Laurence.klotz@sunnybrook.ca
authors.forename: Laurence
authors.initials: L
authors.lastname: Klotz
mesh_terms: D018450:Disease Progression; D055088:Early Detection of Cancer; D019317:Evidence-Based Medicine; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D011159:Population Surveillance; D011237:Predictive Value of Tests; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000473:pathology / Q000628:therapy*; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D019564:Unnecessary Procedures; D057832:Watchful Waiting