Effect of smoking cessation and tobacco type on the risk of cancers of theupper aero-digestive tract in Brazil

Tobacco smoking has long been identified as the most important risk factor for upper aero-digestive tract cancers. To investigate the effect of differ ent tobacco types and the benefit of smoking cessation, we analyzed data fr om a case-control study of 784 cases of mouth, pharynx, and larynx cancers and 1,578 non-cancer controls in three metropolitan hospital areas in Brazi l. Subjects were interviewed as to their smoking and drinking habits, demog raphics, environmental exposures, occupational history, health characterist ics, and diet Controlling for total tobacco and alcohol consumption, risks for ex-smokers compared with current smokers decreased substantially with t ime since cessation of the habit. Compared with never smokers, ex-smokers o f >20 years had a relative risk (RR) of 1.98 [95% confidence interval (CI) = 1.0-3.8] for all upper aerodigestive trace cancers. RRs for long term (>2 0 years) ex-smokers tended re, be lower for mouth (RR = 1.61) and pharynx ( RR = 1.52) than for larynx (RR = 3.63) cancers. The benefit of quitting was strongest fur commercial cigarettes (RR = 1.45, 95% CI = 0.7-3.0) fur ex s mokers of >10 years, as compared with smoking of black tobacco (RR = 2.57, 95% CI = 1.4-4.6), cigars (RR = 2.59, 95% CI = 0.6-11.6), and pipe tobacco (RR = 3.40, 95%, CI = 1.3-8.8).