Combined Analysis of V20, VS5, Pulmonary Fibrosis Score on Baseline Computed Tomography, and Patient Age Improves Prediction of Severe Radiation Pneumonitis After Concurrent Chemoradiotherapy for Locally Advanced Non–Small-Cell Lung Cancer

Introduction:We aimed to develop a more accurate model for predicting severe radiation pneumonitis (RP) after concurrent chemoradiotherapy for non–small-cell lung cancer.Methods:We retrospectively analyzed data from 122 patients with locally advanced non–small-cell lung cancer treated with concurrent chemoradiotherapy. Several dose-volume histogram metrics including absolute lung volume spared from a 5 Gy dose (VS5) were analyzed for an association with RP above NCI-CTC grade 3 (RP ≥ G3). Clinical factors including pulmonary fibrosis score (PFS) and pulmonary emphysema score on baseline chest computed tomography (CT) were also analyzed.Results:Fourteen patients (11.4%) developed RP greater than or equal to G3. On univariate analysis, all dose-volume histogram metrics, sex, and PFS on baseline CT were significantly (p < 0.05) associated with occurrence of RP greater than or equal to G3. Multivariate analysis revealed that V20 greater than or equal to 26%, VS5 less than 1500 cc, age greater than or equal to 68 years, and PFS on baseline CT greater than or equal to 2 were significant risk factors. Thus, we defined a new predictive risk score (PRS) that combines these factors. The cumulative incidence of RP greater than or equal to G3 at 12 months were 0%, 7.8%, 26.6%, and 71.4% when the PRS was 0, 3–5, 6–8, and 9–14, respectively (p < 0.001). This PRS was superior at predicting RP than both V20 and VS5 combined, or V20 alone by receiver operating characteristic analysis (area under the curve, 0.888 versus 0.779 versus 0.678).Conclusions:V20, VS5, age, and PFS on baseline CT are independent and significant risk factors for occurrence of severe RP. Combining these factors may improve the predictability of severe RP