Population-Based Outcomes of Single-Fraction Stereotactic Ablative Radiotherapy for Early Stage Non-small Cell Lung Cancer.

[AIMS] Single-fraction stereotactic ablative radiotherapy (SF-SABR) was introduced in British Columbia (BC), Canada, during the COVID-19 pandemic. It persists as a standard treatment owing to its comparable outcomes with fractionated regimens in two randomised phase II trials and advantages in resource utilisation and patient convenience. This study evaluated the clinical outcomes and toxicities in patients treated with SF-SABR for early stage non-small lung cancer (NSCLC) in BC.

[MATERIALS AND METHODS] This multi-institution population-based retrospective study included all patients treated with SF-SABR for early stage NSCLC between March 2020 and August 2023 in BC. All lesions were peripheral T1-T2 tumours, less than 5 cm in diameter. All patients were medically inoperable or declined surgery. Prescription doses were either 30 Gy or 34 Gy in one fraction. Assessed clinical outcomes included 2-year local failure (LF), distant failure (DF), and overall survival (OS). Toxicity endpoints were graded according to Common Terminology Criteria for Adverse Events version 5.0.

[RESULTS] A total of 179 lesions in 166 patients were included. The median follow-up was 23.0 months. The median age was 75 years. The majority (95%) of tumours were T1. The median tumour diameter was 1.5 cm. 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 chest wall toxicity (CWT) rates were 5.6% and 0.6%, respectively. Chest wall abutment, diabetes, and prior thoracic radiation were significant predictors for CWT on univariate analysis.

[CONCLUSIONS] This multi-institution population-based study demonstrated that SF-SABR for early stage NSCLC had favourable early clinical outcomes and low toxicity rates comparable to data from other SF-SABR and multi-fraction lung SABR studies. Long-term follow-up of outcomes and toxicity for SF-SABR are warranted.