Clinical study of asbestos-related lung cancer in Japan with special reference to occupational history

A total of 152 patients with asbestos-related lung cancer recognized by the criteria of Japanese compensation law for asbestos-related diseases were examined and compared with 431 patients with non-asbestos-related lung cancer. Male comprised 96% of patients. Ages ranged from 50 to 91 years with a median of 72 years. Eighty-nine percent were smokers or ex-smokers. Almost all patients had occupational histories of asbestos exposure. The median duration of asbestos exposure was 31 years and the median latency period was 47 years. Thirty-four percent of patients exhibited asbestosis and 81% exhibited pleural plaques by radiography. Regarding asbestos particles in the lung for 73 operated or autopsied patients, 62% had more than 5,000 particles per gram. On the other hand, 100% of non-asbestos-related lung cancer patients had <5000 particles per gram with a median of 554 particles. The number of asbestos bodies in the lung, male gender, absence of symptoms, smoking index, and early stage of cancer were significantly much more than those of non-asbestos-related lung cancer. In this study, a diagnosis of asbestos-related lung cancer was made in 34% of patients by asbestosis, in 62% by presence of both pleural plaques and more than 10 years' occupational asbestos exposure, and in 4% by more than 5000 asbestos particles per gram of lung tissue. Occupational histories, duration of asbestos exposure, and pleural plaques are common categories for the recognition of asbestos-related lung cancer in Japan.