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

Abstract 

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.

Keywords: Lung cancer, Stage I, Stereotactic radiation therapy, Radiation injury, Computed tomography, Radiation fibrosis