Fluorine-18-α-methyltyrosine positron emission tomography for diagnosis and staging of lung cancer: A clinicopathologic study

Purpose: L-[3-¹⁸F]-α-Methyltyrosine ([¹⁸F]FMT) is an amino acid tracer for positron emission tomography (PET). We evaluated the diagnostic usefulness of [¹⁸F]FMT PET in non-small-cell lung cancer (NSCLC) patients. Tumor uptake of [¹⁸F]FMTwas compared with that of 2-[¹⁸F]-fluoro-2-deoxy-D-glucose ([¹⁸F]FDG) and correlated with L-type amino acid transporter 1 (LAT1) expression. Experimental Design: Fifty NSCLC patients were enrolled in this study, and a pair of PET study with [¹⁸F]FMT and [¹⁸F]FDG was done. LAT1 expression and Ki-67 labeling index of the resected tumors were analyzed by immunohistochemical staining. Results: For the primary tumor detection, [¹⁸F]FMT PET exhibited a sensitivity of 90% whereas the sensitivity for [¹⁸F]FDG PETwas 94%. For lymph node staging, the sensitivity and specificity of [ ¹⁸F]FMT PET were 57.8% and 100%, and those of [¹⁸F]FDG PET were 65.7% and 91%, respectively. The expression of LAT1 in squamous cell carcinoma and large cell carcinoma was significantly higher than that in adenocarcinoma. [¹⁸F]FMT uptake was also higher in squamous cell carcinoma and large cell carcinoma than in adenocarcinoma. Uptake of [ ¹⁸F]FMT in the tumor is closely correlated with LAT1 expression (ρ = 0.890). Conclusion: [¹⁸F]FMT PET had no false-positives in the detection of primary tumor and lymph node metastasis and could improve the diagnostic performance in NSCLC. Uptake of [¹⁸F]FMT correlated with the expression of LAT1 that showed a significant association with cellular proliferation.