Purpose: The differentiation of recurrent lung cancer and post-therapeutic changes remains a problem for radiological imaging, but FDG-PET allows biological characterisation of tissues by visualising glucose metabolism. We evaluated the diagnostic performance and prognostic impact of FDG-PET in cases of suspected relapse of lung cancer.
Methods: In 62 consecutive patients, 73 FDG-PET scans were performed for suspected recurrence after surgical therapy of lung cancer. FDG uptake by lesions was measured as the standardised uptake value (SUV). PET results were compared with the final diagnosis established by biopsy or imaging follow-up. SUV and clinical parameters were analysed as prognostic factors with respect to survival.
Results: FDG-PET correctly identified 51 of 55 relapses and gave true negative results in 16 of 18 remissions (sensitivity, specificity, accuracy: 93%, 89%, 92%). SUV in recurrent tumour was higher than in benign post-therapeutic changes (10.6+/-5.1 vs 2.1+/-0.6, p<0.001). Median survival was longer for patients with lower FDG uptake in recurrent tumour (SUV<11: 18 months, SUV > or = 11: 9 months, p<0.01). Long-term survival was observed mainly after surgical re-treatment (3-year survival rate 38%), even if no difference in median survival for surgical or non-surgical re-treatment was detected (11 vs 12 months, p=0.0627). For patients subsequently treated by surgery, lower FDG uptake predicted longer median survival (SUV<11: 46 months, SUV> or = 11: 3 months, p<0.001). SUV in recurrent tumour was identified as an independent prognostic factor (p<0.05).
Conclusion: FDG-PET accurately detects recurrent lung cancer. SUV in recurrent tumour is an independent prognostic factor. FDG-PET helps in the selection of patients who will benefit from surgical re-treatment.