Nagoya City University Graduate School of Medical Sciences Nagoya, Aichi
N. Kita, N. Tomita, T. Takaoka, M. Ukai, D. Okazaki, M. Niwa, A. Torii, S. Takano, M. Oguri, A. Matsuura, and A. Hiwatashi; Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
Purpose/Objective(s): To identify risk factors and bronchial dose constraints for radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT) in patients with central early-stage non-small cell lung cancer (NSCLC). Materials/
Methods: We reviewed 245 patients with early-stage NSCLC treated with SBRT, and 79 patients with a tumor within 3 cm of the main or lobar bronchus were included in this study. The median prescribed dose and fraction were 50 Gy and 4 fractions, respectively. The primary endpoint was grade = 2 RP. Gray’s test was performed to examine the relationship between clinical risk factors and grade =2 RP, and the Fine-Gray model was used for a multivariate analysis. The effects of each dose parameter on grade =2 RP were evaluated with the Fine-Gray model and optimal thresholds were tested using receiver operating characteristic (ROC) curves. Results: Among a total of 79 patients analyzed. The median age of patients was 77 years. The median follow-up period was 43 months. The 4-year cumulative incidence of grade =2 RP was 22.5% (G2, 11 patients; G3, 6 patients; =G4, none). The multivariate analysis of clinical factors identified age, the location of the lobes, and the solid component diameter as significant factors for grade =2 RP (p = 0.018, 0.005, and 0.002, respectively). Regarding bronchial parameters, V10-V40Gy and D0.1-D5cc correlated with the development of RP. Among all parameters of the bronchus and lung, only bronchial parameters exceeded AUC of 0.72 for grade =2 RP. Parameters with AUC exceeding 0.72 were bronchus V20Gy (AUC, 0.728), V15Gy (AUC, 0.736), and V10Gy (AUC, 0.723), with respective thresholds of 0.41, 1.2, and 1.8 cc. Bronchus V15Gy =1.2 cc serves as the best indicator for the prevention of grade =2 RP. Conclusion: In SBRT for central early-stage NSCLC, bronchus V15Gy =1.2 cc is the definitive indicator for preventing grade =2 RP.
