[Respiratory infectious complications in patients with lung cancer]

Since respiratory infectious complications in lung cancer cases are major obstacles for adequate or intensive anticancer chemotherapy, they often affect prognosis unfavorably. Such respiratory infections secondary to lung cancer generally occur on the basis of defects of the defence mechanism against infections due to disturbance in the clearance system in sites peripheral to bronchial obstruction or stenosis. The lowered concentration of antimicrobial agents at the site of infection, resulting from decreased local pulmonary blood flow, make the infections difficult to manage. Moreover, immunosuppression resulting from the use of anticancer drugs, most of which inevitably possess immunosuppressive effect, become a cause of infections with opportunistic pathogens such as Enterobacteriaceae, glucose nonfermentative bacilli and anaerobes. Since the recent wide and frequent use of 3rd generation cephem antibiotics, an apparent increase in the incidence of staphylococcus aureus as a causative organism has been observed, in contrast to a marked decrease in that of Klebsiella pneumoniae. In patients who received intensive chemotherapy repeatedly or are in the terminal stage, an imbalance of T cell lymphocytes subsets, namely a lowered T+4 vs T+8 ratio, are frequently observed. Under these conditions, pulmonary involvement due to reactivation of a latent virus, i.e. cytomegalovirus and/or protozoa, i.e. Pneumocystis carinii could be a cause of death.