2329 - Outcomes of Single-Fraction Stereotactic Ablative Radiotherapy for Early-Stage Non-Small Cell Lung Cancer: A Multi-Institution Population-Based Study
Presenter(s)
J. M. Callueng1,2, S. Baker2,3, N. Chng2,4, J. P. Abrina1,2, D. B. Hoegler2,5, D. W. Petrik1,2, E. M. Dunne2,6, I. G. Mohamed1,2, R. M. Halperin1,2, S. Atrchian1,2, A. Lin1,2, A. Y. Ye2,4, F. Hsu2,7, D. Schellenberg2,3, M. Liu2,6, and B. Mou2,5; 1BC Cancer Kelowna, Kelowna, BC, Canada, 2University of British Columbia, Vancouver, BC, Canada, 3BC Cancer Surrey, Surrey, BC, Canada, 4BC Cancer Prince George, Prince George, BC, Canada, 5BC Cancer, Kelowna, BC, Canada, 6BC Cancer Vancouver, Vancouver, BC, Canada, 7BC Cancer Abbotsford, Abbotsford, BC, Canada
Purpose/Objective(s): Single-fraction stereotactic ablative radiotherapy (SF-SABR) was first introduced in the province of British Columbia (BC), Canada during the COVID-19 pandemic as a mitigation strategy to minimize clinic visits without compromising outcomes. It has since become a standard treatment option in BC owing to its comparable outcomes with fractionated regimens in two randomized phase II trials and advantages in resource utilization and patient convenience. This population-based study evaluated clinical outcomes and toxicities among all patients in BC treated with SF-SABR for early-stage non-small lung cancer (NSCLC).
Materials/Methods: This multi-institution population-based retrospective study included all patients in BC treated with SF-SABR for early-stage NSCLC between March 2020 and August 2023. All lesions were peripheral T1-T2 tumors, less than 5 cm in diameter. All patients were either medically inoperable or declined surgery. Prescription doses were either 30 Gy or 34 Gy in a single fraction. Assessed clinical outcomes included 2-year local failure (LF), 2-year distant failure (DF), and 2-year overall survival (OS). Toxicity endpoints were graded according to Common Terminology Criteria for Adverse Events version 5.0. OS was computed using the Kaplan-Meier method. LF and DF were calculated using the cumulative incidence function, with death as a competing risk. Binary logistic regression was used to assess for variables associated with toxicity.
Results: A total of 166 patients with 179 lesions were included. Median follow-up was 23.0 months (interquartile range, 16.3-29.2). Median age was 75 years (range, 57-94). The majority (95%) of tumors were T1. Median tumor diameter was 1.5 cm (range, 0.6-4.5). A histologic diagnosis was obtained in 24.6% of lesions. The internal gross tumor volume was abutting the chest wall in 65 (35.8%) lesions. Prescription doses of 30 Gy and 34 Gy were delivered to 103 (57.5%) and 76 (42.5%) lesions, respectively. The 2-year LF, DF, and OS rates were 7.1%, 14.1%, and 81.5%, respectively. No grade 4 or 5 toxicities were reported. Crude rates of grade 2 and 3 toxicities were 17.3% and 2.2%, respectively. Grade 2 and 3 rates of pneumonitis were 3.4% and 0.6%, respectively. Grade 2 and 3 chest wall toxicity (CWT) rates were 5.6% and 0.6%, respectively. The rates of grade 2+ CWT for lesions abutting, = 1 cm, and > 1 cm from the chest wall were 10.9%, 3.5%, and 3.5%, respectively. Chest wall abutment (odds ratio [OR] 4.02, P=0.032), diabetes (OR 5.75, P=0.006), and prior thoracic radiation (OR 4.23, P=0.032) were significant predictors for CWT on univariate analysis.
Conclusion: This multi-institution population-based study demonstrated that SF-SABR for early-stage NSCLC had favorable early clinical outcomes and low rates of toxicity comparable to existing data from other SF-SABR and multi-fraction lung SABR studies. Further follow up is recommended to evaluate the long-term outcomes and toxicity for SF-SABR.