Some nonrandomized studies suggest that early treatment of bladder cancer (BC) provides a survival benefit. For example, asymptomatic individuals with a single finding of ≥ 3 red blood cells per high-power field (AMH) have a 0.0% to 16.1% chance of developing BC [1], with a lower proportion of late-stage tumors than cancer registries and no deaths among screen-detected subjects followed for 2.5 to 8.5 years [2]. Delaying radical cystectomy after diagnosis of muscle-invasive BC decreases patient survival [3]. Finally, screening for urinary cytology (UC) is associated with a statistically nonsignificant increase in survival of approximately 3 years in the first 10 years of follow-up in industrial populations [4]. Therefore, the American College of Physicians [5] and the Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (SUFU) [6] recommend cystoscopy and urinary tract imaging in adults with AMH at intermediate-risk (women >50 years, men >40 years, smoking history >10 pack-years or AMH on repeat urinalysis) and high-risk (age >60 years, >30 pack-years smoking history, >25 RBCs/HPF or a history of gross hematuria) for BC.

The high false-positive rate of AMH and low sensitivity of UC prompted the search for other markers. Recently, a urine DNA methylation assay [7], serum tumor DNA [8], and a serum 4-miRNA panel [9] were found to have greater than 80% sensitivity for BC. However, the proof of screening efficacy requires a randomized trial with mortality as the endpoint. In the absence of such trials [1], BC screening is not recommended for the general population [10].

The longer survival observed in some uncontrolled cohort studies could be confounded by several biases. The first one is selection bias as individuals who voluntarily participate in screening are in better health than those who do not. The second bias is length bias as screening is more likely to detect slow-growing cancers. Third, lead-time bias (LT) is the interval between the detection of cancer by screening asymptomatic individuals and its diagnosis in symptomatic patients, resulting in a "backward extension" of the time between diagnosis and death. The duration of LT of BC is uncertain. Prospective studies have reported a time interval of 14.5 years after the detection of AMH [11] and 3 years after the detection of precancerous lesions of exfoliated urothelial cells [12]. Retrospective studies have reported an interval of up to 7 years from the detection of AMH [11] and up to 10 years after the detection of urinary biomarkers [13]. In this paper, I attempt to derive the LT of BC from the ratio between the prevalence of BC in screening studies and annual incidence rates.