Differential diagnosis of local recurrence from radiation pneumonitis in patients with lung cancer after radiotherapy using 18F-fluorodeoxyglucose PET/CT

초록

1896 Objectives We investigate whether FDG PET/CT can discriminate local recurrence from radiation pneumonitis in patients with lung cancer after radiotherapy. Methods 95 patients (age=62±10y,M:F=74:21,76 NSCLC,20 SCLC) who underwent post-radiotherapy FDG PET/CT were included. Patient’s disease status (local recurrence and/or distant metastasis,n=65;recurrence-free,n=30) was evaluated by image studies and clinical history during follow-up period. FDG uptake of primary lesion and radiation pneumonitis site was measured on pre- and post-radiotherapy, post-radiotherapy FDG PET/CT scan, respectively. Patient group was classified as having local recurrence (RG,n=35), or recurrence-free status (NG,n=30). FDG uptake was represented by maximal standardized uptake value (mSUV). Quantitative analysis for lesion-to-pneumonitis mSUV ratio (LPR) was performed. Results Percent-change of maxSUV in primary lesion after radiotherapy revealed significant difference between RG and NG (mean 6.9% decreased in RG vs. 48.4% decreased in NG, p=0.0227). In RG, primary lesion showed prominent FDG uptake comparing with pneumonitis site (mSUV 10.2±3.9 vs. 3.8±1.5, p<0.0001), but in NG, primary lesion showed no statistical difference from pneumonitis site (mSUV 3.7±2.2 vs. 2.9±1.2, p=0.1034) on post-radiotherapy scan. The LPR was significantly different between RG and NG (3.0±1.8 vs. 1.3±0.6, p<0.0001). Quantitative analysis revealed an LPR of 1.86 was the optimal cutoff value for differential diagnosis (area under the curve 0.890, sensitivity 83.3%, specificity 89.3%) Conclusions Post-radiotherapy FDG PET/CT is effective study for diagnosing local recurrence of patient with lung cancer after radiotherapy