Early and late lung radiographic injury following stereotactic body radiation therapy (SBRT)

Objective: To describe early and late CT patterns of radiographic lung injury after SBRT for lung cancer, and to correlate radiological findings with patient and treatment characteristics. Materials and methods: Follow-up CT scans of 68 patients with 70 tumors were divided into 4 periods: (1) 6 weeks; (2) 2-6 months; (3) 7-12 months and (4) 13-18 months after SBRT. Early (within 6 months) and late radiological injuries were evaluated according to Ikezoe and Koening, respectively. The correlation between CT findings and patient characteristics was evaluated. Results: Radiographic injury in periods 1 and 2 was: (1) diffuse consolidation 3 and 27%, (2) patchy consolidation and ground-glass opacity (GGO) 13.2 and 33%, (3) diffuse GGO 13.2 and 21%, (4) patchy GGO 16.2 and 6%, and (5) no findings 54.4 and 21%, respectively. Late injury in periods 3 and 4 were: (1) modified conventional pattern (consolidation, volume loss, bronchiectasis) 54 and 44%, (2) mass-like 20 and 28%, (3) scar-like 14 and 16% and (4) no findings 20 and 12%, respectively. The proportion of emphysema grades 2-4 was significantly higher in patients who had no radiological findings 6 weeks after treatment (p=0.021). Both patchy consolidation and GGO patterns resulted more frequently in patients who were not administered steroids (p=0.035). No relationship was found with smoking, tumor dimension and radiation dose. Conclusions: The majority of patients had no evidence of radiographic lung injury 6 weeks after SBRT; the most prevalent findings were diffuse or patchy GGO. Patchy and diffuse consolidation develops 2-6 months after SBRT. Modified conventional pattern was the most prevalent in the late periods.