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Tobacco smoking and the risk of upper aero‐digestive tract cancers: A reanalysis of case–control studies using spline models
Author(s) -
Polesel Jerry,
Talamini Renato,
La Vecchia Carlo,
Levi Fabio,
Barzan Luigi,
Serraino Diego,
Franceschi Silvia,
Dal Maso Luigino
Publication year - 2008
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.23385
Subject(s) - medicine , larynx , logistic regression , pharynx , relative risk , risk factor , cancer , digestive tract , cigarette smoking , environmental health , demography , surgery , confidence interval , sociology
Although tobacco smoking has long been recognized as a major risk factor for cancer of the upper aero‐digestive tract (UADT, i.e ., oral cavity, pharynx, larynx, and oesophagus), very few studies have provided estimates of the effect of very low tobacco consumption. Step‐functions have been the common statistical methods for risk estimates, but the choice of reference category and of interval cutpoints influence the results, especially when data are sparse. In the present analysis, the dose–response relationship between UADT cancers and tobacco smoking was evaluated through logistic regression spline models. We included 1,241 UADT male cases and 2,835 male controls pooled from a large series of case–control studies conducted in northern Italy and in the Swiss Canton of Vaud during the last 2 decades. For cancers of the pharynx, larynx and oesophagus, the risk steadily increased with number of cigarettes/day. The risk of oral, pharyngeal and oesophageal cancers was significantly higher in smokers than in nonsmokers beginning with as low as 2 cigarettes/day. The effect of tobacco smoking at low levels seemed less evident for laryngeal cancer since the raise in risk begun with 6 cigarettes/day. In conclusion, for all the examined UADT sites, a monotonic dose–response relationship between cancer risk and cigarette smoking emerged. The excess of risk among people smoking 2 cigarettes/day highlights the absence of any harmless level for cigarette smoking, and it further supports the need of public health programs against tobacco smoking. © 2008 Wiley‐Liss, Inc.