摘要：Background and purpose: Acute exacerbation of interstitial pneumonia is a life-threatening complication after lung cancer surgery. Dorsal subpleural fibrotic changes occupying 3 or more segments of both lower lobes on high-resolution computed tomography indicate a very high risk. We conducted a prospective phase II study to assess the efficacy of prophylactic treatment. Methods: Patients with lung cancer underwent high-resolution computed tomography preoperatively to assess the risk of acute exacerbations of interstitial pneumonia. Before induction of general anesthesia, high-risk patients received 125 mg of methylprednisolone as an intravenous bolus and sivelestat sodium hydrate 300 mg ·day(-1) as a continuous intravenous infusion. From January 2010 through August 2011, a total of 327 patients underwent surgery for lung cancer, and 31 (9.5%) were enrolled. Results: There was no case of acute exacerbation. No adverse events were associated with prophylaxis. Usual interstitial pneumonia was confirmed histopathologically in 25 (80.6%) patients. Four (12.9%) patients had major complications. Usual interstitial pneumonia was diagnosed postoperatively in 4 (1.4%) of 327 patients who did not meet the inclusion criteria, and 1 of these patients died due to acute exacerbation of occult interstitial pneumonia. Conclusion: Perioperative use of sivelestat sodium hydrate and low-dose methylprednisolone may be useful as prophylaxis for acute exacerbation of interstitial pneumonia.