Is 18F-3'-fluoro-3'-deoxy-L-thymidine useful for the staging and restaging of non-small cell lung cancer?

The objective of this study was to compare 18F-3'-fluoro-3'-deoxy-L-thymidine (FLT) PET with clinical TNM staging, including that by 18F-FDG PET, in patients with non-small cell lung cancer (NSCLC). METHODS: Patients with NSCLC underwent whole-body 18F-FDG PET and whole-body 18F-FLT PET, using a median of 360 MBq of 18F-FDG (range, 160-500 MBq) and a median of 210 MBq of 18F-FLT (range, 130-420 MBq). 18F-FDG PET was performed 90 min after 18F-FDG injection, and 18F-FLT PET was performed 60 min after 18F-FLT injection. Two viewers independently categorized the localization and intensity of tracer uptake for all lesions. All 18F-FDG PET and 18F-FLT PET lesions were compared. Staging with 18F-FLT PET was compared with clinical TNM staging based on the findings of history, physical examination, bronchoscopy, CT, and 18F-FDG PET. From 8 patients, standardized uptake values (SUVs) were calculated. Maximal SUV and mean SUV were calculated. RESULTS: Sixteen patients with stage IB-IV NSCLC and 1 patient with strong suspicion of NSCLC were investigated. Sensitivity on a lesion-by-lesion basis was 80% for the 8 patients who received treatment before 18F-FLT PET and 27% for the 9 patients who did not receive pretreatment, using 18F-FDG PET as the reference standard. Compared with clinical TNM staging, staging by 18F-FLT PET was correct for 8 of 17 patients: 5 of 9 patients in the group with previous therapy and 3 of 8 patients in the group without previous therapy. The maximal SUV of 18F-FLT PET, at a median of 2.7 and range of 0.8-4.5, was significantly lower than that of 18F-FDG PET, which had a median of 8.0 and range of 3.7-18.8 (n = 8; P = 0.012). The mean SUV of 18F-FLT PET, at a median of 2.7 and range of 1.4-3.3, was significantly lower than that of 18F-FDG PET, which had a median of 6.2 and range of 2.8-13.9 (n = 6; P = 0.027). CONCLUSION: 18F-FLT PET is not useful for staging and restaging NSCLC.