P1.16-26 Safety of SABR (Stereotactic Ablative Body Radiotherapy) for Central Non-Small Cell Lung Cancers (cNSCLC) with 50 Gray in 5 Fractions (50Gy/5f)

SABR using 60Gy/3f (or equivalent) caused high toxicity when used for cNSCLC. To determine a safe SABR dose for cNSCLC, the phase I/II RTOG 0813 trial used 50Gy/5f as a baseline. From 2013, 50Gy/5f was adopted for inoperable early-stage cNSCLC at the West of Scotland Cancer Centre, a tertiary-level oncology unit. We report our prospectively collected toxicity and efficacy data. Patients with cNSCLC were identified from the radiotherapy database. cNSCLC was defined as lung cancers within 2cm of the proximal bronchial tree, or the planning target volume (PTV) abutting the mediastinal pleura/pericardium. Patient and treatment characteristics were obtained from electronic medical records. All patients received 50Gy/5f on alternate days with a volumetric arc therapy plan using TrueBeam linear accelerators. Toxicity was assessed in a centralised follow-up clinic 2 weeks, 6 weeks, 3 months, 6 months, 1 and 2 years after treatment using Common Toxicity Criteria Adverse Events version 3. Patients had a CT scan at 3 months post-treatment. Subsequent CT scans were at the discretion of the treating clinician. 50 patients (31 females, 19 males, median age 75.1 years old) were identified with T1-2N0M0 cNSCLC. 84% were medically unfit for surgery. 40% had biopsy-proven NSCLC. All patients completed treatment on schedule. Two patients died within 90 days of treatment, one from a chest infection, the other cause of death was unknown. Table 1 describes the early and late toxicity. Over a median follow-up of 24 months, there were 20 deaths, 8 unrelated to cancer, and 12 due to cancer recurrence. The median progression free survival and overall survival are 26.0 months (95% confidence interval: 16.4, 35.6 months) and 28.6 months (95% confidence interval: 21.3, 35.8 months) respectively. This study has demonstrated that 50Gy/5f is a safe dose and fractionation for early-stage inoperable cNSCLC, with outcomes comparable to other series.