The prognostic role of pulmonary emphysema for radiation pneumonitis (RP) after stereotactic body radiotherapy was investigated. It is true that patients with pulmonary emphysema showed a lower rate of abnormal shadow, but there was no association with Grade 2 to 3 RP. This is because patients with pulmonary emphysema had a low tolerance for symptomatic RP because of poor pulmonary function. Background: The aim of this study was to determine the prognostic factors of radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT). Patients and Methods: A total of 50 patients (36 male and 14 female) were treated with SBRT for 42 primary lung cancers and 8 metastatic lung cancers. SBRT was performed with 48 Gy in 4 fractions to the isocenter or with 40 Gy in 4 fractions covering 95% of the planning target volume. Percentage of low attenuation area (%LAA) was defined as percentage of the lung area with attenuation of −860 Hounsfield units (HU) or lower (%LAA-860) or of −960 HU or lower (%LAA-960). The dosimetric parameter of V 20 Gy , which means percentage volume of the lung receiving 20 Gy or more, was recalculated. RP was assessed using Common Terminology Criteria for Adverse Events version 4.0. Results: The median follow-up period was 39.0 months (range, 7.2-94.5 months). RP of Grade 0, Grade 1, and Grade 2 to 3 was diagnosed in 11, 29, and 10 patients, respectively. Multivariate analyses (MVA) for Grade 1 showed that higher %LAA-860 and higher %LAA-960 were significantly associated with a lower rate of Grade 1 RP. MVA for Grade 2 to 3 showed that lower Brinkman index and lower lung V 20 Gy were significantly associated with a lower rate of Grade 2 to 3 RP, and, in contrast, %LAA-860 and %LAA-960 had no association with Grade 2 to 3 RP. Conclusion: This result suggests that high %LAA is associated with radiological changes (Grade 1) but that %LAA has no correlation with Grade 2 to 3 RP because symptomatic RP might also be affected by other factors.
- Low attenuation area
- Predictive factor
- Radiation-induced lung toxicity