Tobacco smoking is one of the main risk factors for oral, pharyngeal and oesophageal
cancers in developed countries. Information on the role of the tar yield of cigarettes
in upper digestive tract carcinogenesis is sparse and needs to be updated because
the tar yield of cigarettes has steadily decreased over the last few decades.
We analysed two case-control studies, from Italy and Switzerland, conducted between
1992 and 1999, involving 749 cases of oral and pharyngeal cancer and 1770 controls,
and 395 cases of squamous-cell oesophageal carcinoma and 1066 matched controls. Odds
ratios (ORs) were estimated by unconditional multiple logistic regression models,
including terms for age, sex, study centre, education and alcohol consumption.
Based on the brand of cigarettes smoked for the longest time, the multivariate ORs
for current smokers compared with never smokers were 6.1 for <20 mg and 9.8 for >or=20
mg tar for oral and pharyngeal neoplasms, and 4.8 and 5.4 for oesophageal cancer,
respectively. For the cigarette brand smoked in the previous six months, the ORs for
>or=10 mg compared with <10 mg were 1.9 for cancer of the oral cavity and pharynx
and 1.8 for oesophageal cancer, after allowance for number of cigarettes and duration
of smoking.
The present study confirms the direct relationship between the tar yield of cigarettes
and upper digestive tract neoplasms, and provides innovative information on lower
tar cigarettes, which imply reduced risks compared with higher tar ones. However,
significant excess risks were observed even in the lower tar category, thus giving
unequivocal indications for stopping smoking as a priority for prevention of upper
digestive tract neoplasms.