Evaluation of lung cancer by 99mTc-tetrofosmin SPECT: comparison with [18F]FDG-PET

The purpose of this study was to clarify the validity of (99m)Tc-tetrofosmin SPECT (TF-SPECT) in the evaluation of lung cancer in comparison with [18F]fluorodeoxyglucose ([18F]FDG-PET).

Twenty-one patients with biopsy-proven non-small cell lung cancer were examined by both TF-SPECT (early and delayed images) and FDG-PET within a week of each study. Lung cancers were analyzed visually and semiquantitatively using the ratio of lesion to background counts (L/B ratio). Mediastinal lymph node metastases were analyzed only visually.

Both early and delayed TF images could detect 18 of 21 lung cancers on visual analysis (85.7%), whereas FDG-PET could detect all the lesions (100%). The L/B ratio of TF-SPECT was significantly higher in delayed than in early images (1.79 +/- 0.55 vs. 1.56 +/- 0.40; p < 0.001). However, the L/B ratio of FDG-PET was 8.85 +/- 3.05, significantly higher than those of both TF images (p < 0.0001). In the assessment of mediastinal involvement, TF-SPECT was 40.0% sensitive, 100% specific, and 71.4% accurate, whereas FDG-PET was 80.0% sensitive, 81.8% specific, and 81.0% accurate.

Although the detection sensitivity was far better than expected, TF-SPECT is not considered to be an alternative to FDG-PET in the evaluation of malignant pulmonary lesions because of its significantly low L/B ratio. TF-SPECT has poor sensitivity for mediastinal lymph node metastases and is useless for staging patients with lung cancer.