Lead-time in prostate cancer screening (Finland)

Objective: Lead-time in prostate cancer screening was estimated using data from the Finnish randomized, population-based trial. Methods: Lead-time was defined as the duration of follow-up needed to accrue the same expected number of incident prostate cancer cases in the absence of screening as detected in the initial screening round. Expected numbers were calculated using an age-cohort model. Results: Based on findings among 10,000 men screened in 1996-1997 with 292 screen-detected cancers, lead-time was estimated as approximately 5-7 years, depending on the reference rates used. This corresponds to a mean duration of the detectable preclinical phase (DPCP) of 10-14 years, given that the cancers were detected on average at the midpoint of the DPCP. Conclusions: The findings suggest that a screening interval substantially longer than the 2 years generally used for mammography screening is unlikely to cause a substantial loss of sensitivity. A long screening interval is further justified in order to diminish the extent of overdiagnosis, until mortality effects can be evaluated.