Administration of an anticancer drug such as Iressa (generic name: gefitinib) or Tarceva (generic name: erlotinib) causes a serious side effect called diffuse alveolar damage in some cases. Also in acute exacerbation of idiopathic pulmonary fibrosis, the serious side effect called diffuse alveolar damage is caused in some cases. Diffuse alveolar damage shows resistance to treatment, has a recurrent nature, and exhibits repeated exacerbation during treatment, resulting in serious exacerbation at an early stage. Thus, diffuse alveolar damage is a symptom to which very careful attention should be paid.
Japanese are reported to develop such diffuse alveolar damage at high frequency (Non-patent Document 1). For example, in cases of gefitinib, the frequency is 0.3% according to surveys in countries other than Japan, while the frequency is 3.98% in Japanese, which indicates a not less than 10 times higher frequency in Japanese. In cases of erlotinib, the frequency is 0.2% according to surveys on Asians, while the frequency is 2.7% according to a survey on Japanese, which again indicates a not less than 10 times higher frequency in Japanese. Further, Japanese patients with idiopathic pulmonary fibrosis are reported to show a higher rate of acute exacerbation and a higher case fatality rate than patients in other countries (Non-patent Document 2). It has been assumed that the number of deaths due to diffuse alveolar damage in Japan is as much as several thousand per year. It should be noted, of course, that death due to the side effect of drugs is a serious problem also in countries other than Japan, apart from its frequency.