Abstract
Purpose: The purpose of this study was to evaluate the CT appearance of radiation injury to the lung and clinical symptoms after SRT (stereotactic radiation therapy) for small lung cancers.
Methods and Materials: In this analysis, 35 patients with 39 primary or metastatic lung cancers were enrolled. The follow-up at the time of evaluation ranged from 6 to 44 months (median 18 months). SRT was performed by 3D conformal method which focuses a single high dose to the tumor. We evaluated the CT appearance of acute radiation pneumonitis (within 6 months) and radiation fibrosis (after 6 months) after SRT. Clinical symptoms were evaluated by CTCAE ver.3.0.
Results: CT appearance of acute radiation pneumonitis was classified as follows; 1) diffuse consolidation in 12 lesions (30.7%), 2) patchy consolidation and ground-grass opacities (GGO) in 6 lesions (15.4%), 3) diffuse GGO in 5 patients (12.8%), 4) patchy GGO in 1 lesion (2.6%), 5) no evidence of increasing density in 15 lesions (38.5%). CT appearance of radiation fibrosis was classified as follows; 1) modified conventional pattern (consolidation, volume loss and bronchiectasis similar to, but less extensive than conventional radiation fibrosis) in 18 lesions (46.2%), 2) mass-like pattern (focal consolidation limited around the tumor) in 10 lesions (25.6%), 3) scar-like pattern (linear opacity in the region of the tumor associated with volume loss) in 11 lesions (28.2%). Eleven of 15 lesions which had no evidence of increasing density of acute radiation pneumonitis progressed to scar-like pattern of radiation fibrosis. Most of these patients had pulmonary emphysema. Patients who were diagnosed more than Grade 2 pneumonitis were significantly more in diffuse consolidation pattern than in other pattern (p=0.00085). Patients who were diagnosed more than Grade 2 pneumonitis were significantly less in no evidence of increase density pattern than in other pattern (p=0.0026).
Conclusion: CT appearance after SRT was classified into five patterns of acute radiation pneumonitis and three patterns of radiation fibrosis. Most of patients who were classified into no evidence of increasing density of acute radiation pneumonitis progressed to scar-like pattern of radiation fibrosis, and had pulmonary emphysema. Most of these patients were not also diagnosed more than grade 2 pneumonitis, therefore we are able to suggest these patients were good candidate for SRT.
