Tobacco and Public Health - TCSC Indonesia

12-year follow-up of the American Cancer Society Cancer Prevention Study I, which
included over one million individuals, a total of 109 deaths from laryngeal cancer was
recorded among men and 22 among women (Burns et al. 1996). On the other hand,
case–control studies are based on incident cases and have often been conducted in
high-risk areas, such as southern Europe and South America.
Cigarette smoking
PAOLO BOFFETTA 369
Among men, the risk of laryngeal cancer is increased 5–10 times among ever cigarette
smokers as compared to never smokers. In population-based series, the proportion of
cases who report not having smoked during their lifetime is in the order of 1–5%. In all
studies that have analysed it, a positive trend was found between amount of smoking
and risk of laryngeal cancer relative to that of non-smokers. Table 21.1 summarizes the
results of the selected case–control studies. Additional studies provided similar results
for other populations, e.g. Uruguay (De Stefani et al. 1995), Spain (Lopez-Abente et al.
1992), and Denmark (Olsen et al. 1985), but they did not fulfil the criteria for inclusion
in Table 21.1. The heterogeneity in the results can be explained by the small number of
non-smoking cases in some of the studies, by the type of tobacco smoked, by differences
in the interactive effect of alcohol drinking, and possibly by differences in genetic
susceptibility factors, in addition to differences in the quality of the studies and the
validity of the results.
Results from cohort studies are comparable to those available from case–control
studies (e.g. Doll and Hill 1954; Dorn 1959; Burch et al. 1981). As an example, Fig. 21.1
shows the relative risk among white men and women enrolled in the American Cancer
Society Cancer Prevention Study I (Burns et al. 1996).
Several cohort and case–control studies reported a positive dose–response according
to duration of smoking (Falk et al. 1989; Restrepo et al. 1989; Sankaranarayanan et al.
1990; Choi and Kahyo 1991; Lopez-Abente et al. 1992; Zheng et al. 1992; Dosemeci
et al. 1997). For example, in the study by Zheng et al. (1992) from China, the odds
ratios were 1.4 (95% confidence interval [CI] 0.4–4.6), 4.1 (1.6–11.1), 12.0 (4.8–30.1),
and 13.2 (5.6–31.2) for less than 20 years, 20–29 years, 30–39 years, and 40 or more
years of smoking.
Selected results on the effect of quitting are summarized in Table 21.2. No protective
effect is apparent during the first five years after quitting, a phenomenon that can be
partially explained by quitting because of early symptoms of the neoplastic lesion.
After that time, however, there is strong evidence of a decrease in risk of laryngeal cancer.
A higher relative risk was suggested in several studies for deep inhalation of tobacco
smoke, as compared to light or no inhalation (Restrepo et al. 1989; Lopez-Abente et al.
1992; Burns et al. 1996; Lewin et al. 1998). In a study from Uruguay, smokers of
hand-rolled cigarettes had a higher risk than smokers of manufactured cigarettes
(De Stefani et al. 1992). Studies from southern Europe and South America have
consistently reported a 1.5- to 2-fold stronger risk among smokers of black-tobacco