Early Graphical Appearance of Radiation Pneumonitis Correlates With the Severity of Radiation Pneumonitis After Stereotactic Body Radiotherapy (SBRT) in Patients With Lung Tumors

Purpose: To investigate factors associated with Grade ≥3 radiation pneumonitis (RP) in patients with lung tumors treated with stereotactic body radiotherapy (SBRT). Methods and Materials: We retrospectively analyzed 128 patients with 133 lung tumors treated with SBRT. RP was graded according to the Common Terminology Criteria for Adverse Events version 3.0. Univariate analyses were used to identify predictive factors for RP. Results: The median follow-up period after SBRT was 12 months (range, 5-45 months). Incidences of Grades 0, 1, 2, and 3 RP were 27%, 52%, 16%, and 5%, respectively. No patients suffered Grade 4 or 5 RP. For all patients with Grade 2 or 3, symptoms occurred either simultaneously with or subsequent to graphical appearances. The latent period was the only significant factor associated with Grade ≥3 RP (p < 0.01). A latent period of 1 or 2 months indicated a 40% (6/15) risk for Grade 3. However, the risk for Grade 3 was 1.2% (1/82) 3 months after SBRT. No pretreatment clinical or dosimetric factors were significantly associated with Grade ≥3 RP. However, 4 of 7 patients with Grade 3 RP had severe pulmonary comorbidities. Conclusion: Only the latency period was a significant factor in the development of RP. No pretreatment clinical or dosimetric factors were significantly associated with Grade ≥3 RP. Patients, especially those with severe pulmonary comorbidities, should be carefully observed for the graphical appearance of RP within a few months during the follow-up period after SBRT.