BIOMARKER STATUS PREDICTS FOR LOCAL CONTROL (LC) FOLLOWING SPINE STEREOTACTIC BODY RADIOTHERAPY (SBRT) IN NON-SMALL CELL LUNG CANCER (NSCLC) PATIENTS WITH SPINAL METASTASES

Report of spine SBRT outcomes in NSCLC patients and impact of death-ligand 1 (PD-L1) status and epidermal growth factor (EGFR) mutation on LC. METHODS: 165 patients and 389 spinal segments were retrospectively reviewed. Primary endpoint was LF and secondary outcomes included overall survival (OS) and vertebral compression fracture (VCF) rates. RESULTS: Median follow-up, OS and age was 13 months (range, 0.5-95 months), 18.4 months (95% CI 11.4-24.6), and 67 years (range, 28.2-89.9) respectively. 52% were female and 76% had adenocarcinoma. 29% had an EGFR mutation, 16% were PD-L1 ≥ 50%, 20% PD-L1 1-49% and 35% PD-L1 <1%. Of 389 segments, 79% were denovo. At baseline, 35% had VCF, 27% epidural disease and 27% paraspinal extension. 61% were treated with 24 or 28 Gy in 2 SBRT fractions. LF cumulative incidence (CI) at 2-years was 25.4% (95% CI 20.9%-30%). EGFR positivity (p<0.0001), PD-L1≥50% (p=0.013) and treatment with IO within 1 month of SBRT (p=0.004) predicted for LC on multivariable analysis (MVA). The 2-year LF rate in EGFR-positive vs. negative patients were 17.7% vs. 28.8%, and in those PD-L1 ≥50% vs PD-L1<50% were 7.8% vs. 38.1%. CI of VCF at 2-years were 8.8% (95% CI 6.1-12.0%). Prior SBRT to the same segment (P<0.0001) and baseline VCF (p<0.0001) were predictors on MVA. CONCLUSION: We identify predictability of EGFR mutation, PD-L1 ≥50% and peri-SBRT IO on LC following spine SBRT in NSCLC.