Risk Factors for Radiation Pneumonitis in Lung Cancer Patients with Subclinical Interstitial Lung Disease after Thoracic Radiation Therapy

Abstract

Background: Previous studies have found that patients with subclinical interstitial lung disease (ILD) are more susceptible to developing radiation pneumonitis (RP) after thoracic radiation therapy. The present study aimed to evaluate the incidence of and risk factors for RP after thoracic intensity-modulated radiation therapy (IMRT) in lung cancer patients with subclinical ILD.Methods: We retrospectively analyzed lung cancer patients with subclinical ILD who were treated with thoracic IMRT with a prescribed dose of ≥50 Gy in our institutions between January 2016 and December 2017.Results: A total of 87 consecutive lung cancer patients with subclinical ILD were selected for the study. The cumulative incidence of grades ≥2 and ≥3 RP at one year was 51.0% and 20.9%, respectively. In the multivariate analysis, the mean lung dose (MLD) ≥12Gy was a significant risk factor for grade ≥2 RP (p = 0.049). Chemotherapy with gemcitabine in the past，V5≥50%，and subclinical ILD involving ≥25% of lung volume were significantly associated with grade ≥3 RP (p = 0.046, p = 0.040, and p = 0.024, respectively).Conclusion: MLD is a significant risk factor for grade ≥2 RP. Lung cancer patients who have received chemotherapy with gemcitabine in the past, V5, and those with subclinical ILD involving ≥25% of lung volume have an increased risk of grade ≥3 RP in lung cancer patients with subclinical ILD.