[Postoperative interstitial pneumonia in primary lung cancer patients--its causes and management]

Eight patients who developed interstitial pneumonia after surgery for primary lung cancer were reviewed to investigate its causes and the key points in treatment. These patients accounted for 1.8% of 633 operated lung cancer patients at our institution over the last 9 years. Risk factors such as bilateral recurrent laryngeal nerve palsy, preoperative chemoradiotherapy, and extensive mediastinal involvement were present in all of them. Pneumonia developed on the nonoperated side in all patients between the 2nd and 45th postoperative day (mean: 18 days). In most of the patients, faint reticular shadows initially appeared in the lower lobe of the nonoperated lung, rapidly spread to the upper lobe, and finally affected the whole lung. Among these eight patients, the initial five patients died because steroids were only administered after the pneumonia had become widespread, whereas the last three patients received early steroid therapy and were saved. The findings that 1) this pneumonia originated from the lower lobe of the nonoperated lung where blood flow is highest postoperatively, 2) the eosinophil count increased just before the onset of pneumonia, and 3) early steroid therapy and immunosuppressive therapy were effective suggest that an allergic or autoimmune mechanism may play some role in its development. When characteristic reticular shadows appear in the lower lobe on the nonoperated side in a lung cancer patient, even if not associated with any symptoms, an early diagnosis of interstitial pneumonia and initiation of steroid therapy is mandatory to ensure survival.