Delayed F-18 FDG uptake in PET distinguishes between TB and malignant lung lesion: Determination of the optimal cut-off level using ROC analysis

Abstract

1742

Objectives: The role of a delayed FDG-PET scan in lung lesion has not been established. We prospectively investigated whether the dual-phase FDG-PET was useful for the differentiation between malignant and TB lung lesion, and determined the best cut-off value.

Methods: 133 consecutive patients (male 92, femle 41, age 59±9.6) with lung lesions underwent dual-phsed FDG-PET. Maximum SUV at 1 hour (SUV1) and 2 hour (SUV 2) following the injection of FDG were determined, and the retention index (RI) was calculated by dividing the difference between SUV2 and SUV1 by SUV1(RI=(SUV2-SUV1)/SUV X 100%).

Results: A diagnosis of lung malignancy was histologically confirmed in 87 patients (65.4%) (69 primary lung cancer,18 lung metastasis). In the other 46 patients (34.6%) was histologically confirmed TB lesion. The SUV1, SUV2, and RI of the malignant lung lesions were significantly higher than those of the TB lung lesions. (SUV1, 5.9+/- 3.2 vs 3.0+/1.1; SUV2, 7.2+/-4 vs 3.1+/-1.3, RI, 23.6 +/-17 vs 3.2 +/-4.3).The AUC values for SUV1, SUV2 and RI were 0.79,(95% confidence intercal [CI], 0.72-0.86), 0.88 (95% CI, 0.82-0.93), and 0.92 (95% CI, 0.86-0.96). The AUC values of SUV2 and RI were significantly higher than those of SUV1 (SUV1 vs SUV 2, P=0.000; SUV1 vs RI, p=0.001; SUV2 vs RI, P=0.236). The best cut off value of SUV2 and RI were 3.9 and 11.8.

Conclusions: Dual-phase F-18 FDG PET using a combination of early and delayed image was shown to be useful in differentiating TB from malignant lung lesions.