Risk factors for in‐hospital mortality in patients with advanced lung cancer with interstitial pneumonia undergoing systemic chemotherapy: A retrospective and observational study using a nationwide administrative database in Japan

BACKGROUND: The safety profile of systemic chemotherapy for lung cancer patients with interstitial pneumonia (IP) in clinical practice remains unclear. Using Diagnostic Procedure Combination (DPC) data from the Japanese administrative database, we investigated the mortality of hospitalized lung cancer patients with IP as they underwent a course of systemic chemotherapy nationwide. METHODS: The DPC data of patients with stage IIIB or IV lung cancer as defined by the Union for International Cancer Control Tumor‐Nodes‐Metastases 6th and 7th editions from April 2014 to March 2016 were obtained. Among those patients, only patients with concomitant IP and receiving systemic chemotherapy without radiotherapy were included. RESULTS: Among 1524 included patients, 70 (4.6%) died in the hospital. Multivariate analysis revealed that low activities of daily living (ADL) scores on admission (hazard ratio [HR] 2.26, 95% confidence interval [CI] 1.24–4.12, p = 0.008) and high‐dose corticosteroid therapy following chemotherapy (HR 2.62, 95% CI 1.44–4.77, p = 0.002) were strongly associated with in‐hospital mortality. It was determined that patients possibly received high‐dose corticosteroids for IP exacerbations; these patients had a higher in‐hospital mortality rate of 67.7% (21/31 patients) and a significantly shorter median survival time of 55 days (95% CI 31–69 days, p < 0.001) than those who did not receive high‐dose corticosteroids. CONCLUSION: Acute exacerbation of IP treated with systemic high‐dose corticosteroids is significantly associated with in‐hospital mortality, and a low ADL score on admission is a risk factor for in‐hospital mortality in lung cancer patients with IP who undergo systemic chemotherapy.