The impact of characteristics of cigarette smoking on urinary tract cancerrisk - A meta-analysis of epidemiologic studies

BAGKGROUND, Although narrative reviews have concluded that there is strong support for an association between cigarette smoking and urinary tract canc er, the association has never been quantified systematically in reviews. Th e purpose of this systematic review was to summarize and quantify the impac t of different smoking characteristics (status, amount, duration, cessation , and age at first exposure) both unadjusted and adjusted for age and gende r. METHODS. The authors included 43 epidemiologic studies (8 cohort and 35 cas e-control) and calculated summary odds ratios (SORs) by meta-regression ana lyses for different smoking characteristics. They also evaluated changes in summary estimates according to differences in study methodology. RESULTS, Smoking status and increased amount and duration of smoking were a ssociated with a strong increased risk of urinary tract cancer. Smoking ces sation and age at first exposure were negatively associated with the risk o f urinary tract cancer. The age- and gender-adjusted SORs for current and f ormer cigarette smokers compared with those for nonsmokers were 3.33 (95% c onfidence interval [CI], 2.63-4.21) and 1.98 (CI, 1.72-2.29), respectively. Even though the component studies differed in methodology, the results wer e rather consistent. CONCLUSIONS. The results suggest a substantial increase in risk of cancer o f the urinary tract for cigarette smokers. Based on the results of this stu dy and previous literature, the authors conclude that current cigarette smo kers have an approximately threefold higher risk of urinary tract cancer th an nonsmokers. In Europe, approximately half of urinary tract cancer cases among males and one-third of cases among females might be attributable to c igarette smoking. (C) 2000 American Cancer Society.