Stereotactic body radiotherapy (SBRT) for non-small cell lung cancer (NSCLC): Is FDG-PET a predictor of outcome?

Background and purpose Distant metastases are the dominant mode of failure after stereotactic body radiotherapy (SBRT) for early-stage non-small cell lung cancer (NSCLC). The primary study objective was to evaluate if the maximum standardized uptake value (SUVmax) on pre-treatment FDG-PET/CT predicted clinical outcomes. Secondary objectives were to correlate 3-month post-SBRT SUVmax and change in SUVmax with outcomes. Materials and methods Consecutive patients with medically inoperable early-stage NSCLC and an FDG-PET/CT scan before (n=82) and 3months after (n=62) SBRT. Results Median follow up was 2years. On univariate analysis baseline SUVmax predicted for distant failure (p=0.0096), relapse free survival (RFS) (p=0.037) and local failure (p=0.044). On multivariate analysis baseline SUVmax predicted for RFS (p=0.037). Baseline SUVmax of above 5 was the most statistically significant cut off point for predicting distant failure (p=0.0002). Baseline SUVmax ⩾4.75 (median) was correlated with a higher risk of distant failure (p=0.012) and poorer RFS (p=0.04). Patients with a post-SBRT SUVmax ⩾2 and a reduction of <2.55 had a significantly higher rate of distant failure. Conclusions Pre-SBRT SUVmax on FDG-PET/CT correlated most strongly with distant failure. A cut off of ⩾5 was the most significant. Post-SBRT SUVmax ⩾2 and a reduction of <2.55 were associated with a higher risk of distant failure.