COMPARISON OF FLUORINE-18-FDG PET AND TL-201 SPECT IN EVALUATION OF LUNG-CANCER

We compared the diagnostic value of [(18)]2-fluoro-2-deoxy-D-glucose ( FDG) PET imaging and Tl-201 SPECT imaging in the detection of primary lung cancer and mediastinal lymph node metastases. Methods: Thirty-thr ee patients with histologically-proven primary lung cancer were examin ed with both FDG PET and Tl SPECT (early and delayed scans) within a w eek of each study. For semiquantitative analysis, the tumor-to-nontumo r activity ratio (T-to-N ratio) was calculated. Results: Although both techniques delineated focal lesions with an increase in tracer accumu lation in 28 patients, PET identified three additional patients in who m TI SPECT images did not visualize any lesions on both early and dela yed 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 TI 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 rat io and the thallium T-to-N ratio (p < 0.01). Twenty-two patients had t horacotomies. Regarding the staging of mediastinal nodes, FDG PET dete cted mediastinal lymph node metastasis that was negative on TI SPECT, whereas both techniques excluded tumor involvement in enlarged node at CT. Conclusion: Both techniques have clinical value for the noninvasi ve detection of primary lung cancer that is 2 cm or greater in diamete r. However, if a PET camera is available, FDG PET is considered the me thod of choice for the evaluation of patients with suspected primary l ung cancer that is less than 2 cm in diameter.