Predictive factors for symptomatic radiation pneumonitis in 293 consecutively treated non-small cell lung cancer (NSCLC) patients receiving definitive radiation therapy.

Abstract

7041 Background: Radiation pneumonitis is a potentially fatal complication in NSCLC patients treated with definitive radiotherapy. The ability to identify patients at risk for this complication would be of value to clinicians. The objective of this study was to identify significant predictors of grade 2 or higher radiation pneumonitis. Methods: Consecutive NSCLC patients receiving definitive non-stereotactic radiotherapy at the University of Pennsylvania between January 2003 to July 2010 were graded for post-treatment radiation pneumonitis using RTOG criteria. Demographic and treatment data were collected on all patients. Univariate and mutivariate analysis was used to determine predictors of grade 2 or higher pneumonitis. Results: Of 293 patients treated in this period, 47% were male, 52% received concurrent chemotherapy. Median prescription dose was 66.6Gy, median gross tumor volume was 91cc, and the median mean lung dose (MLD) was 16Gy. On univariate analysis, concurrent chemoradiation (p = 0.002; OR 2.7), MLD (p = 0.0001, OR = 1.14/Gy), KPS (p = 0.045, OR = 1.04/point), and N2/3 disease (p = 0.026, OR = 2.51) were significant predictors of pneumonitis. A multivariate analysis including all significant predictors on univariate analysis was performed and only MLD (p = 0.031, OR = 1.10/Gy) proved significant. The median MLD cutoff of 16Gy had a sensitivity/specificity of 72% and 55% respectively and positive and negative predictive value of 55% and 87% respectively. Of note, V20 (volume of lung receiving 20Gy or higher), smoking status, and pre-treatment pulmonary function tests including FEV1 and DLCO were not significant predictors of pneumonitis. Conclusions: MLD was a significant predictor of grade 2 or higher radiation pneumonitis in patients with NSCLC receiving definitive radiotherapy, while V20 was not. Additionally, the poor positive predictive value and specificity of MLD limits the clinical utility of this variable. This study underscores the need for more robust predictors of radiation pneumonitis.