Smoking and renal cell carcinoma.

The relationship between smoking habits and the risk of renal cell carcinoma was investigated in a case-control study conducted in northern Italy on 131 cases of histologically confirmed cancers of the renal parenchyma (85 males, 46 females) and 394 controls in hospital for acute, nonneoplastic, nonurological disorders. Compared with never smokers, the relative risk (RR) was 1.7 (95% confidence interval = 1.0-3.1) among ex-smokers. A direct and significant dose-risk relationship was observed among current smokers, with RR of 1.1, 1.9, and 2.3 for moderate, intermediate, and heavy smokers. This trend in risk was statistically significant (chi2(1) = 5.04; P = 0.02). The risk was directly related to duration of smoking (RR = 1.7 for less than 30 versus 1.8 for greater than or equal to 30 years, P = 0.04), and inversely with age at starting (RR = 2.0 for less than or equal to 20 versus 1.7 for greater than 20 years) and, among ex-smokers, with time elapsed since stopping (RR = 2.2 for less than 10 versus 1.3 for greater than or equal to 10 years). This pattern of risk, together with the absence of appreciable confounding, adds further evidence for a causal nature of the association between smoking and renal cell cancer.