Comparison of 18F-FLT PET and 18F-FDG PET for detection of cervical lymph node metastases in head and neck cancers

Abstract

Conclusion: Despite low uptake of tracer, 3′-deoxy-3′-18F-fluorothymidine (FLT) PET could detect cervical lymph node metastases as well as 2-deoxy-2-18F-fluoro-d-glucose (FDG) PET. Objective: The diagnostic efficacy of FLT PET was compared with that of FDG PET regarding nodal staging of head and neck squamous cell cancers. Methods: Twenty-three patients were examined with FLT PET and FDG PET. PET images were evaluated qualitatively for regions of focally increased metabolism and maximum standardized uptake values (SUV) were calculated for semiquantitative analysis. Results: The mean (± SD) FLT SUV in visualized metastatic lymph nodes was 4.8 ± 2.9 as compared with 6.9 ± 4.9 for FDG SUV (p < 0.001). Significant correlations were found between the area of metastatic lymph nodes and both FLT SUV (r = 0.8; p < 0.0001) and FDG SUV (r = 0.84; p < 0.0001). The false-positive (over-staged) and false-negative (under-staged) rates for lymph node staging by FLT PET were 4% (1/23) and 17% (4/23), respectively. Those for FDG PET were 9% (2/23) and 13% (3/23). All metastatic lymph nodes measuring more than 9 mm in short-axis diameter were correctly detected by FLT PET. However, both FLT and FDG PET had low sensitivity for detecting the lymph node metastases ≤ 9 mm in short-axis diameter and tumor deposits < 5 mm.