P2.12-18 Interstitial Lung Abnormalities are a Risk Factor for Radiation Pneumonitis in Patients with Limited-Stage Small-Cell Lung Cancer

Abstract

Previous studies reported that patients wth preexisting radiological interstitial lung abnormalities (ILAs) were more susceptible to developing radiation pneumonitis (RP) after thoracic radiation therapy (TRT). The present study aimed to evaluate the incidence and predictors of RP after TRT in patients with limited-stage small-cell lung cancer (LS-SCLC) with or without preexisting radiological ILAs. A total of 183 consecutive patients with LS-SCLC between January 2015 and December 2016, who were treated with thoracic intensity-modulated radiation therapy at our institution, were analyzed. The diagnosis of ILAs was reviewed by two experienced thoracic radiologists based on the pretreatment high-resolution computed tomography(CT) imaging, such as honeycombing, subpleural reticular opacities, ground-glass opacity, and traction bronchiectasis. Univariate and multivariate analyses were used to assess the correlation of clinical factors, preexisting radiological ILAs, and dose-volume histogram-based dosimetric parameters with RP. The correlation between the preexisting ILAs score on CT findings and the grade of RP was analyzed by Pearson Correlation. Twenty (10.9%) patients had preexisting radiological ILAs. The median follow-up time was 10.9 months. RP was observed in 75 (41.0%), 35 (19.1%), 11 (6.0%), and 0 (0%) patients with grades 1, 2, 3, and ≥4 RP, respectively. The incidence of ≥ grade 2 and 3 RP at 1 year was 26.3% and 6.2% in the entire cohort, respectively. Preexisting radiological ILAs were associated with an increased risk of ≥grade 2 RP (84.1% in ILAs + vs 18.7% in ILAs-, P＜0.001) and ≥ grade 3 RP (27.7% in ILAs + vs 3.8% in ILAs-, P ＜0.001) at 1 year. Preexisting radiological ILAs was a significant predictors of ≥grade 2 RP and ≥grade 3 RP in multivariate analysis (P ＜0.001, P = 0.004, respectively). Lower forced expiratory volume in 1 second was a significant predictor of ≥grade 2 RP in multivariate analysis (P = 0.043). The ratio of CD4 and CD8 cells has a tendency to predict ≥grade 3 RP in multivariate analysis (P = 0.053).There was a moderate correlation between the preexisting ILAs score on CT findings and the grade of RP (Pearson Correlation Coefficient = 0.364, P ＜0.001). Preexisting radiological ILAs is associated with an increased risk of ≥grade 2 RP and ≥grade 3 RP after TRT in patients with LS-SCLC.