Pulmonary dose-volume predictors of radiation pneumonitis following stereotactic body radiation therapy

Publication date: Available online 4 February 2016
Source:Practical Radiation Oncology
Author(s): Eileen M. Harder, Henry S. Park, Zhe (Jay) Chen, Roy H. Decker
PurposeRadiation pneumonitis (RP) may be severe after stereotactic body radiation therapy (SBRT). Our purpose was to identify pulmonary and cardiac dosimetric parameters that predicted for post-SBRT Grade ≥2 RP.Methods and Materials335 patients with ≥3 months follow-up were included. Normal pulmonary volume was total lungs minus gross tumor volume. Pulmonary Dmax (maximum dose), MLD (mean lung dose), and Vx (% lung receiving ≥x Gy) for 5-50Gy in 5Gy increments were collected. Cardiac Dmax, mean dose, V0.1, V0.25-V1, and V2.5-V12.5 were recorded. Multivariable logistic regression (LR) with manual backward stepwise elimination was used to identify the best dosimetric predictors of toxicity. Optimal dose-volume cutoffs were isolated with recursive partitioning analysis (RPA).ResultsThe Grade ≥2 RP rate was 18.8%. Pulmonary V5-V50, MLD, and cardiac V0.1-V2.5 were significantly associated with toxicity on univariate analysis. On multivariable LR, V10 was the strongest dosimetric predictor of Grade ≥2 RP (odds ratio 1.052, 95% confidence interval=1.014-1.092, p=0.007). RPA identified a 21.6% risk of Grade ≥2 RP with V10 ≥6.14% (vs. 3.8% with <6.14). MLD was the most significant predictor of Grade ≥3 RP (OR 1.002, 95% CI 1.000-1.003, p=0.031). RPA identified a 25.0% risk of Grade ≥3 RP with MLD ≥7.84Gy (vs. 8.0% when <7.84Gy).ConclusionsWith a Grade ≥2 RP rate of 18.8%, lung V10 was the best predictor of Grade ≥2 toxicity. MLD was the best predictor of Grade ≥3 RP.



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