Persistence of urothelial carcinoma of the bladder risk among former smokers: results from a contemporary, prospective cohort study.

Objectives: Cigarette smoking is a known risk factor for urothelial carcinoma (UC) of the bladder. However, the persistence of an increased risk for UC following smoking cessation is not well established. We assessed the risk of UC among former smokers using a recent, prospective cohort with a high proportion of former smokers.

Materials And Methods: Study participants were members of the VITamins And Lifestyle cohort (VITAL), a group of 77,719 men and women between the ages of 50 and 76 years from western Washington State. Smoking history and other risk factors were obtained at the time of recruitment. The primary outcome was a new diagnosis of UC (n =385), as determined through linkage to a population-based cancer registry.

Results And Limitations: The cohort included 8% current and 44% former smokers, and among the UC cases, 15% were current and 60% former smokers. Both the current and former smoker had an increased risk of UC compared with never smokers (hazard ratio [HRs]: 3.81; 95% confidence intervals [CI] 2.71-5.35 and 2.0; 95% CI 1.55-2.58, respectively). Among former smokers, the risk of UC increased with the pack-years smoked and decreased with the years since quitting. When both the measures of smoking were considered together, the risk of UC was similar for long-term quitters and recent quitters for a given level of pack-years. For example, for those with pack-years of 22.5-37.5, the HR of UC was 1.91 (95% CI 1.17-3.11) for the distant quitters (≥ 23.5 y before baseline) and HR = 1.92 (95% CI 1.26-2.94) among the recent quitters. Limitations include the small number of cases at the extremes of smoking history and errors in self-reported smoking history.

Conclusions: The risk of bladder cancer in former smokers remains elevated>32 years after quitting, even among those with moderate smoking histories. This argues that a history of smoking confers a lifelong increased risk of UC.