Repeated Stereotactic Body Radiotherapy for Lung Malignancies: Toxicity Can Be Reduced by Sparing Lung Irradiation

Abstract

Background/Aim: Evidence on the use of repeated stereotactic body radiotherapy (SBRT) is limited. We investigated the efficacy of repeated SBRT and predictors of lung toxicity. Patients and Methods: We reviewed 20 patients (27 lesions) with primary or metastatic lung cancer who underwent repeated SBRT with CyberKnife^®. We generated a composite plan for dosimetric analysis based on equivalent doses in 2.0-Gy fractions (α/β=3). Predictors of Grade 2+ radiation pneumonitis (RP) were examined. Results: The median follow-up duration was 18.0 months. The 1-year and 2-year local control were both 95.2%. Five patients (25%) developed Grade 2+ RP, including a Grade 5 RP. The Grade 2+ RP group showed higher composite mean lung dose (MLD) and lower lung volumes spared from 5-20 Gy (VS5-VS20). Conclusion: Repeated SBRT with CyberKnife^® showed favorable local control, but a high rate of Grade 2+ RP. Accumulated MLD and VS5-VS20 may predict RP.