We compared the diagnostic value of [18F]2-fluoro-2-deoxy-D-glucose (FDG) PET imaging and 201Tl SPECT imaging in the detection of primary lung cancer and mediastinal lymph node metastases.
Methods: Thirty-three patients with histologically-proven primary lung cancer were examined with both FDG PET and TI SPECT (early and delayed scans) within a week of each study. For semiquantitative analysis, the tumor-to-nontumor activity ratio (T-to-N ratio) was calculated.
Results: Although both techniques delineated focal lesions with an increase in tracer accumulation in 28 patients, PET identified three additional patients in whom Tl SPECT images did not visualize any lesions on both early and delayed scans. In the detection of lung cancer of less than 2 cm in size, FDG PET provided higher sensitivity (six of seven, 85.7%) than did Tl SPECT early scan (one of seven, 14.3%) and delayed scan (four of seven, 57.1%). Neither technique visualized any lesions in two patients who had bronchioloalveolar carcinoma. The T-to-N ratio was significantly higher with FDG PET (10.39 +/- 6.63) than it was with Tl SPECT (early scan, 2.37 +/- 0.86; delayed scan, 3.01 +/- 1.01) (p < 0.0001), whereas there was significant positive correlation between the FDG T-to-N ratio and the thallium T-to-N ratio (p < 0.01). Twenty-two patients had thoracotomies. Regarding the staging of mediastinal nodes, FDG PET detected mediastinal lymph node metastasis that was negative on Tl SPECT, whereas both techniques excluded tumor involvement in enlarged node at CT.
Conclusion: Both techniques have clinical value for the noninvasive detection of primary lung cancer that is 2 cm or greater in diameter. However, if a PET camera is available, FDG PET is considered the method of choice for the evaluation of patients with suspected primary lung cancer that is less than 2 cm in diameter.