Abstract
Introduction: Tobacco use is a rising concern for the developing world. It causes about 5million deaths yearly and is projected to cause 10 million deaths yearly by 2025 with 80% of these deaths from the developing countries if current trends continue. Tobacco is also a majo risk factor for all kinds of cancer including Liver cancer.
Goal: To help determine whether the risk of liver cancer from smoking was less or greater than other forms of cancers caused by tobacco.
Methods: In this study, we ascertained retrospectively the smoking habits of 24,000 adults who had died from liver cancer (cases) in 10 Chines cities, 7 Indian Cities and 5 Nigerian Cities. These areas were choosen for reasons of high population. Smokers from these three countries constitute 40% of smokers worldwide. Calculations of the smoker risk ratios (RR) for liver cancer mortality were standardised for age and locality. We used Cox proportional hazard regression models to adjust for confounding variables. We conducted analyses on the entire study population, among male and females who had smoked for at least 20 years separately for each country.
Results: Among adult men (aged 35+) there was a 36% excess risk of death from liver cancer (smoker standardised risk ratio [RR] =1.36, with 95% confidence interval [Cl] 1.29–1.43, 2p<0.00001; attributable fraction 18%). In the general male population, this indicates absolute risks of death from liver cancer before age 70 of about 4% in smokers (in the absence of other causes). The RR was approximately independent of age, was similar in urban and rural areas, was not significantly related to the age when smoking started but was significantly (p<0.001) greater for cigarette smokers than for smokers of other forms of tobacco. Among men who smoked only cigarettes, the RR was significantly (p<0.001 for trend) related to daily consumption, with a greater hazard among those who smoked 20/day (RR 1.50, 95% CI 1.39–1.62) than among those who smoked fewer (mean 10/day: RR=1.32, 95% Cl 1.23–1.41). Smoking was also associated with a significant excess of liver cancer death in women (RR 1.17, 95% CI 1.06–1.29, 2p=0.003; attributable fraction 3%), but fewer women (17%) than men (62%) were smokers, and their cigarette consumption per smoker was lower. Among women who smoked only cigarettes, there was a significantly greater hazard among those who smoked at least 20/day (mean 22/day: RR=1.45, 95% Cl 1.18–1.79) than among those who smoked fewer (mean 8/day: RR=1.09, 95% Cl 0.94–1.25).
Conclusion: This study goes to show that even though liver cancer from tobacco use kills about 200,000 people yearly in these three developing countries, the deaths from lung cancer (1.5 million yearly worldwide) is still higher than liver cancer deaths.
Citation Information: Cancer Prev Res 2010;3(1 Suppl):B142.
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