Comparison of FLT PET and FDG PET for the evaluation of primary head and neck cancer

Objectives The nucleoside analogue 3'-deoxy-3'-¹⁸F-fluorothymidine(FLT) has been introduced for imaging cell proliferation with positron emission tomography (PET). We investigated the feasibility of FLT PET for detection of primary head and neck cancer in comparison with 2-deoxy-2-¹⁸F-fluoro-D-glucose (FDG) PET.

Methods A total of 35 patients with newly diagnosed primary head and neck cancer were examined with both FLT and FDG PET. The tumor site was epipharynx in 4, mesopharynx in 7, hypopharynx in 10, larynx in 8, and tongue in 6. PET imaging was performed at 60 minutes after each radiotracer injection. Tumor lesions were identified as areas of focally increased uptake, exceeding that of background uptake. For visualized lesions, the maximum standardized uptake value (SUV) was calculated. All semi-quantitative data were expressed as mean±SD.

Results All 35 primary head and neck cancer showed focally increased uptake of both FLT and FDG. The mean values of FLT SUV in carcinoma of mesopharynx (5.9±3.2), hypopharynx (6.2±3.0), larynx (4.3±2.8), and tongue (6.9±4.4) were significantly lower than the corresponding values of FDG SUV in carcinoma of mesopharynx (10.2±6.1), hypopharynx (13.4±4.4), larynx (6.8±2.1), and tongue (10.7±5.6), respectively (p<0.05). There was no significant difference between FLT SUV (6.9±3.1) and FDG SUV (12.6±2.9) in carcinoma of epipharynx.

Conclusions FLT PET could visualize primary head and neck cancer although uptake of FLT in primary tumor was significantly lower than that of FDG.