Primary lung cancer and asthma.

6,021 40-year-old and older chronic asthma suffers, seen during the past 20 years, were analyzed with regard to the development of primary lung cancer and their smoking habits. Over this period only two developed lung cancer, 0.032% as compared with 0.314% in the general population. Only 16.9% of chronic asthmatics had smoked over any significant period during the five years prior to assessment as compared with approximately 40% of the general population. Of those who did smoke, the tendency was to a lesser extent. This survey adds further evidence that cancer develops less frequently in patients suffering from an allergic disease such as asthma, perhaps because of (1) some enhanced immunological activity preventing the advent of new growth or (2) reduced smoking habits of chronic asthmatics.