Tumor Control and Survival Outcomes Based on Maximum Standardized Uptake Value on FDG-PET/CT in T1-2 NSCLC Treated With SBRT

Abstract

<h3>Purpose/Objective(s)</h3> Stereotactic body radiotherapy (SBRT) is standard of care in medically inoperable early-stage non-small cell lung cancer (NSCLC). Assessment of maximum standardized uptake value (SUVmax) on FDG-PET/CT before and after SBRT may stratify tumor control and survival outcomes. <h3>Materials/Methods</h3> Retrospective chart review identified patients with T1-2N0M0 NSCLC who were only treated with SBRT between 2012 and 2019. Pretreatment SUVmax and percent change in SUVmax at 3 and 6 months following SBRT were assessed as independent predictors of local control (LC), regional failure-free survival (RFFS), distant failure-free survival (DFFS), progression-free survival (PFS), and overall survival (OS). Receiver operator characteristic (ROC) analysis yielded optimal cut points for comparison. Survival analyses were performed with Kaplan-Meier estimates with log rank testing, and Cox proportional hazards models including age, sex, T stage, histology, and performance status. <h3>Results</h3> 71 (43.6%) out of 163 patients underwent repeat PET/CT within 6 months of SBRT completion. Median follow-up was 19 months (range 1 – 94 months). For the whole cohort, 1-year and 2-year LC, PFS, and OS were 95.0% and 80.3%, 75.9% and 47.7%, and 87.1% and 67.0%, respectively. For DFFS, pretreatment SUVmax greater than 4 had an aHR of 3.33 (95% CI 1.42 – 7.84, <i>P</i> = 0.006). Pre-SBRT SUVmax over 12.3 had an aHR of 2.80 (95% CI 1.3 – 6.2, <i>P</i> = 0.011) for PFS, and a cut point of 12.6 had an aHR of 3.00 (95% CI 1.6 – 5.8, <i>P</i> = 0.003) for OS. Pretreatment SUVmax did not significantly predict LC or RFFS. At 3 months following SBRT, an SUVmax decrease of at least 45% was associated with improved LC (aHR = 0.15, 95% CI 0.02 – 0.91, <i>P</i> = 0.018). A 6-month SUVmax decrease of more than 53% was associated with better LC (<i>P</i> = 0.038), and a decrease over 11% was associated with improved RFFS (aHR = 0.12, 95% CI 0.02 – 0.96, <i>P</i> = 0.046). Change in SUVmax was not significantly associated with DFFS, PFS, or OS at either time point. No factors other than performance status for PFS and OS were significant. <h3>Conclusion</h3> At 3 and 6 months following SBRT, cut points for percentage change in SUVmax can stratify risk of local recurrence and possibly regional recurrence. Pretreatment SUVmax cutoffs can predict distant failure, progression-free survival, and overall survival in early-stage NSCLC.