Follow-up or surveillance ¹⁸F-FDG PET/CT and survival outcome in lung cancer patients

The value of performing follow-up PET/CT imaging more than 6 mo after the conclusion of therapy - either as a routine practice or because of clinically suspected recurrence - is not well established. The purpose of this study was to evaluate the added value of followup PET/CT to the clinical assessment and survival outcome of lung cancer patients. Methods: This was a retrospective study of 261 biopsy-proven lung cancer patients at a single tertiary center. In total, 488 follow-up PET/CT scans done 6 or more months after the completion of initial treatment were included in this study. Median follow-up from the completion of primary treatment was 29.3 mo (range, 6.1-295.1 mo). Overall survival (OS) benefit was measured using Kaplan-Meier plots with a Mantel-Cox log-rank test. A multivariate Cox regression model was provided with clinical covariates. Results: Of the 488 PET/CT scans, 281 were positive and 207 negative for recurrence. Overall median survival from the time of the PET/CT study was 48.5 mo. The median survival of PET-positive and PETnegative groups was 32.9 and 81.6 mo, respectively (P < 0.0001). A subgroup analysis demonstrated a similar difference in OS for 212 scans completed between 6 and 24 mo after treatment (P = 0.0004) and 276 scans completed after 24 mo (P = 0.0006). In the context of clinical assessment, PET/CT identified recurrence in 43.7%(107/245) of scans without prior clinical suspicion and ruled out recurrence in 15.2% (37/243) of scans with prior clinical suspicion. There was a significant difference in OS when grouped by clinical suspicion (P = 0.0112) or routine follow-up (P < 0.0001). In a multivariate Cox regression model, factors associated with OS were age (P < 0.0001) and PET/CT result (P = 0.0003). An age-stratified subgroup analysis demonstrated a significant difference in OS by PET scan result among patients younger than 60 y and between 60 and 70 y but not in those older than 70 y (P < 0.0001, P = 0.0004, and P = 0.8193, respectively). Conclusion: ¹⁸F-FDG PET/CT performed for follow-up more than 6 mo after the completion of primary treatment adds value to clinical judgment and is a prognostic marker of OS in lung cancer patients, regardless of the timing of the follow-up scan, and especially in patients younger than 70 y.