Global perspective of tobacco habits and lung cancer: a lesson for third world countries

Over the past 50 years, a dominant role of tobacco smoking in lung cancer c ausation has been demonstrated. Almost three-quarters of the lung cancer ca ses can be attributed to tobacco smoking. The global variation in lung canc er incidence is thought to be directly proportional to the smoking habits p revalent in that part of the world. Lung cancer shows a greater upward tren d in incidence in the USA, in central and Eastern Europe than ever before, especially in females. Japan too has recorded a Ill-fold increase in incide nce in both sexes since 1975. In India the problem is further compounded by absence of authentic data on time trend. The recent trend of available dat a suggests a more or less linear trend. At present lung cancer ranks among the top three killers in men in almost every metropolis in India, The highe st incidence rate has been recorded in Bombay (14.6/ 100,000) and the lowes t in Barshi (2.0/100,000), How much of these can be attributed to smoking c annot be commented on as no case-control or cohort studies have ever been u ndertaken in India. The situation is more alarming in other developing coun tries, where there is no authentic data on tobacco use or lung cancer incid ences. The relationship between tobacco and cancer is both simple and complex. The majority of the cancer patients are smokers, while the cancer incidence is not proportional among smokers. To explain this, various factors such as t ype of smoke, duration of smoke, amount of carcinogens, presence of activat ion and metabolism pathways, and lately genetic environment interaction, ha ve been put forward. It appears that the relationship is more complex than at first thought. In developing countries, it is further compounded by lack of data on usage and dependence of the economies of these countries on tob acco. The situation is alarming, with ever-increasing incidence among women and non-smokers exposed to smoke (passive smokers). Tobacco use has alread y become an epidemic. (C) 1999 Lippincott Williams & Wilkins.