Overdiagnosis of prostate carcinoma by screening: An estimate based on theresults of the Florence Screening Pilot Study

Objectives: To estimate overdiagnosis (detection of latent carcinomas) as a consequence of screening for prostate cancer. Design: Based on actual screen (first or repeat) detected and interval pros tate cancer rates observed in the Florence screening pilot study, a scenari o was simulated where males aged 60 years (or 65) had six biennal screens a nd were followed up for four years. Overdiagnosis was determined as the pro portional excess of cancers detected by screening with respect to that expe cted in its absence. Setting: City of Florence, Italy, from 1992 through 1995. Population: 2,740 resident males, aged 60 to 74 years. Results: Overdiagnosis was estimated to be 51% (95% confidence limits: 44%- 55%) or 93% (85%-101%) for age 60 or 65 at entry. Comparison with other scr eening experiences obtaining higher detection rates suggests that a more ag gressive screening approach could be associated with overdiagnosis estimate s as big as 200%-250%. Conclusions: Screening for prostate cancer is associated with a relevant ri sk of overdioagnosis. As latent carcinomas can not be presently identified, this would lead to overtreatment in most overdiagnosed cases. The negative consequences of overdiagnosis (knowledge of having a cancer) and of overtr eatment (impotence, incontinence, perioperatory death) may be extremely ser ious. In absence of any scientific evidence of screening benefits (if any) screening should not be recommended as a current practice, but should be li mited to prospective controlled studies designed to assess its cost-effecti veness.