近半世纪以来欧美许多国家肺癌的发病率有明显的提高。在英国,肺癌约占男性癌症死亡总数的一半;在美国,占1/3左右。据上海市市区居民的调查,1960～1976年,肺的发病率上升了5倍多;在全部恶性肿瘤中,已从第六位跃升到第二位。肺癌的确切病因尚不清楚,但是大家公认长期大量吸烟较不吸烟者患肺癌的危险性增加10～50倍。因此,近年来有些国 The incidence of lung cancer in many countries in Europe and America has improved significantly in the past half century. In the United Kingdom, lung cancer accounts for about half of all male cancer deaths; in the United States, it accounts for about 1/3. According to a survey of urban residents in Shanghai, from 1960 to 1976, the incidence of lung disease increased more than five-fold; among all malignancies, it has jumped from sixth to second. The exact cause of lung cancer is not yet clear, but it is generally accepted that the risk of lung cancer increases by a factor of 10 to 50 in long-term smokers compared to non-smokers. Therefore, some countries in recent years