Comparison of FLT-PET and FDG-PET for Visualization of Head and Neck Squamous Cell Cancers

We compared 3'[F-18]fluoro-3'-deoxythymidine (FLT) positron emission tomography (PET) and 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) for PET visualization of head and neck squamous cell cancers (HNSCCs) and evaluated which might better reflect proliferative activity as indicated by the Ki-67 index. A total of 43 patients with HNSCCs were examined with FLT-PET and FDG-PET. The PET images were evaluated qualitatively for regions of focally increased metabolism and for semiquantitative analysis the maximum standardized uptake value (SUV) was calculated. For depiction of primary tumours, the sensitivity of both approaches was 100%. The mean (+/- SD) SUV for FLT (5.65 +/- 2.96) was significantly lower than that for FDG (10.9 +/- 4.91; p < 0.0001). No significant differences were found for the T category. However, the mean (+/- SD) FLT SUV was significantly higher in poorly than in well-differentiated tumours (6.49 +/- 3.13 vs. 4.2 +/- 2.08; p < 0.04). Similarly, FDG SUVs in poorly and moderately differentiated tumours (12.72 +/- 4.8 and 11.46 +/- 4.64) were significantly higher than in well-differentiated tumours (7.45 +/- 3.51; p < 0.004 and p < 0.02). No significant correlation was observed with the Ki-67 index for either. FLT-PET showed as high a sensitivity as FDG-PET for the detection of primary HNSCC lesions, although uptake of FLT was significantly lower than that of FDG.