18F-FAMT uptake correlates with tumor proliferative activity in oral squamous cell carcinoma: comparative study with 18F-FDG PET and immunohistochemistry

Objective L-3-[F-18]-fluoro-alpha-methyl tyrosine (FAMT) is transported into cancer cells by L-type amino acid transporter 1 (LAT1). The purpose of the present study is to correlate the uptake of FAMT and FDG with the cellular proliferative activity measured by the Ki-67 labeling index (Ki-67 LI) in oral squamous cell carcinoma (OSCC). Methods Twenty-five patients with OSCC were enrolled in this study. Both FAMT-PET and FDG-PET were performed within 4 weeks before surgery in all cases. The uptake of FAMT and FDG was compared by semiquantitative analysis with maximal standardized uptake values (SUVmax) of the primary tumors. Ki-67 LI of the tumors was analyzed by immunohistochemical staining and correlated with the clinicopathologic variables and the uptake of PET tracers. Results For primary tumor detection, FAMT-PET exhibited a sensitivity of 84%, whereas that of FDG-PET was 88%. In all visible lesions, mean FDG uptake determined by average SUVmax was 9.7 (range 4.2-15.9) and mean FAMT uptake was 3.5 (range 1.3-8.5). The SUVmax of FAMT tended to show a better correlation with Ki-67 LI (r = 0.878) than that of FDG (r = 0.643). Conclusions Uptake of FAMT correlated with cellular proliferation of OSCC. FAMT-PET may be a useful procedure to evaluate tumor proliferation of OSCC.