Effect of Treatment Delivery Schedule for Patients With Early-Stage Non-Small Cell Lung Cancer Treated With Stereotactic Ablative Radiation Therapy: A Population-Based Analysis.

Purpose: The optimal SABR treatment delivery schedule in stage I non-small cell lung cancer (NSCLC) remains unclear. This population-based study investigated grade ≥2 toxicity rates, local failure (LF), and overall survival (OS) in patients treated with 48 Gy in 4 fractions scheduled every other day versus daily with weekends and consecutive daily without weekends.

Methods and materials: Between January 2019 and June 2022, treatment records using 48 Gy in 4 fractions were extracted from a provincial cancer registry and grouped by delivery as every other day, daily with weekends, or consecutive daily without weekends. Toxicity events were recorded using National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0. The Kaplan-Meier method was used to compute OS and LF was calculated using cumulative incidence methods with death as a competing risk. Cox regression analyses and Fine-Gray modeling was used to assess for variables associated with OS and LF, respectively.

Results: Of 404 patients meeting study criteria, 190, 111, and 103 received SABR every other day, daily with weekends, and consecutive daily without weekends, respectively. More patients receiving SABR daily with weekends were medically inoperable and more patients receiving SABR consecutive daily without weekends had tumors abutting the chest wall. Median follow-up time was 29.5 months (IQR, 19.2-38.4 months). Overall toxicity was low, with crude rates of acute and late grade ≥2 toxicity not being statistically different among the groups. No grade 4 or 5 toxicities were recorded. LF rates at 24 months were not different at 7.5% (95% CI, 3.7-11.3), 9.5% (95% CI, 3.9-15.1), and 11.0% (95% CI, 4.9-17.2) for the every other day, daily with weekends, and consecutive daily without weekends groups, respectively (P = .60). Schedules of daily with weekends and consecutive daily without weekends were not associated with LF. Similarly, no significant differences in median OS were found among the every other day, daily with weekends, and consecutive daily without weekends groups at 47.5 months (95% CI, 39.26-55.74), 52.7 months (95% CI, 34.7-70.7), and 49.0 months (95% CI, 31.6-66.4), respectively. Schedules of daily with weekends and consecutive daily without weekends were not associated with OS.

Conclusions: This population-based study demonstrated no statistically significant differences in grade ≥2 toxicity rates, LF, and OS for patients with stage I NSCLC treated with lung SABR using 48 Gy in 4 fractions delivered every other day, daily with weekends, and consecutive daily without weekends. Patient convenience and optimization of resources may be considered when choosing a lung SABR treatment delivery schedule.