[Epidemiology of malignant tumors of the larynx and lung].

Respiratory tract cancers, unlike most other cancers, have known causes and are susceptible to primary prevention. According to a large population-based case-control study in Southern Europe, over 90% of the present incidence of laryngeal cancer could be prevented by avoiding smoking and alcohol consumption. Most of the risk is attributable to tobacco, but reducing alcohol alone could still prevent a quarter of the cases. Tobacco smoking, on the other hand, explains 80 to 90% of lung cancer incidence in Italy. Other known causal factors include: occupational exposures, which, according to several studies, may account for one third of the cases in the highly industrialized areas of Northern Italy; environmental pollution; passive smoking; radon; and dietary factors. Factors associated to a diet rich in fruit and vegetables have been found to be protective for both larynx and lung cancer in several studies carried out in Italy and elsewhere. The factors associated to this diet may be a major determinant in the North/South gradient in incidence and mortality consistently observed in geographical and migrant studies on respiratory cancers in Italy. Cigarette smoking, however, remains by far the most important cause of respiratory cancer, and geographical and temporal trends in incidence can easily be interpreted in terms of market trends, both in Italy and worldwide. According to several population surveys in Italy, the prevalence of smokers in successive male cohort generations reached a maximum (almost 80%) in the 1920-1930 birth cohorts and decreased to about 60% among males born in the forties and fifties. In the same period, the mean number of cigarettes per day for smokers increased, and the age of starting smoking decreased; however, the market changed from unfiltered black tobacco to filtered low-tar cigarettes. This market trend is consistent with the observation of decreasing incidence and mortality of both larynx and lung cancer in young male cohorts and the persistent increase of both cancers in older males. As for women, the prevalence of smokers increased from less than 10% in the 1920's birth cohorts to over 30% among women born in the late forties. This is reflected by a steady increase of respiratory cancers mortality which, however, is still lower than the mortality for males.