Clinical Outcomes And Predictors Of Lung Toxicity After Multiple Courses Of Lung Stereotactic Body Radiotherapy For Early-Stage Non-Small Cell Lung Cancer

Lung stereotactic body radiotherapy (SBRT) is a well-established modality for inoperable non-small-cell lung cancer (NSCLC). However, multicourse lung SBRT has not been validated in a prospective trial. In our single-institutional experience with multicourse lung SBRT, we found favorable outcomes and identified composite lung V-5 (proportion of lung structure receiving at least 5 Gy) and timing of the second course of SBRT to be potentially related to the development of radiation pneumonitis.Background: The clinical outcomes of multicourse lung stereotactic body radiotherapy (SBRT) have yet to be validated in a prospective study, and there are a lack of data on allowable composite dosimetry. Patients and Methods: Forty-four patients underwent multicourse lung SBRT for recurrent or metachronous NSCLC. The median biologically effective dose (BED10) for the first course and subsequent courses were 132 and 100 Gy, respectively. Patient and treatment characteristics were evaluated to determine the correlation with the development of radiation pneumonitis (RP). Results: The local control rate was 91%. A total of 13.6% developed a grade 2+ RP, and 4.5% developed a grade 3+ RP, including one grade 5. On univariable analysis, multiple composite dosimetric factors (V-5 [proportion of lung structure receiving at least 5 Gy], V-10, V-20, V-40, and mean lung dose) were correlated with the development of RP. When comprised of the first and second course of SBRT, a composite lung V-5 of < 30% and > 50% was associated with a 0 and 75% incidence of grade 2+ RP, respectively. We identified no significant correlation on multivariable analysis but observed a strong trend between composite lung V-5 and the development of grade 2+ RP (hazard ratio, 1.157; P = .058). Evaluation of multiple clinical factors also identified a significant correlation between the timing of repeat lung SBRT and the development of grade 2+ RP after the second course (P = .0028). Conclusion: Subsequent courses of lung SBRT, prescribed to a median BED10 of 100 Gy, can provide a high rate of local control with a 4.5% incidence of grade 3+ toxicity. Composite lung V-5 and the timing of the second course of lung SBRT may be correlated to the development of RP. (C) 2020 Elsevier Inc. All rights reserved.