Clinical significance of 18F-α-methyl tyrosine PET/CT for the detection of bone marrow invasion in patients with oral squamous cell carcinoma: comparison with 18F-FDG PET/CT and MRI

L-3-[F-18]-fluoro-alpha-methyl tyrosine (F-18-FAMT) is an amino acid tracer for positron emission tomography/computed tomography (PET/CT) which specifically transported into cancer cells by L-type amino acid transporter 1 (LAT1). LAT1 overexpression in tumors is significantly correlated with cell proliferation and angiogenesis. F-18-FAMT PET/CT, fluorine-18-fluorodeoxyglucose (F-18-FDG) PET/CT and magnetic resonance imaging (MRI) were compared for their diagnostic performance in the detection of bone marrow invasion in patients with oral squamous cell carcinoma (OSCC). Twenty-seven patients with OSCC on the upper or lower alveolar ridge underwent staging by MRI, F-18-FDG PET/CT and F-18-FAMT PET/CT studies before surgery. Post-surgical pathologic examination was used as the standard to determine the final diagnoses. The possibility of bone marrow invasion on MRI, F-18-FDG PET/CT and F-18-FAMT PET/CT were usually graded retrospectively into five-point score. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated according to the obtained scores. As the sensitivity of F-18-FDG PET/CT was highest (100 %) among that of MRI (95 %) and F-18-FAMT PET/CT (90 %), the specificity of F-18-FAMT PET/CT was highest (85.7 %) among that of MRI (57 %) and F-18-FDG PET/CT (14.3 %). The size of pathological tumor was accorded with that detected by F-18-FAMT PET/CT and was smaller than that detected by F-18-FDG PET/CT (P < 0.01). Significant difference was not found between F-18-FAMT PET tumor volume and pathological tumor volume. F-18-FAMT PET/CT was useful and more specific than MRI or F-18-FDG PET/CT in the detection of bone marrow invasion of OSCC and may contribute to minimize the extent of resection in oral surgery patient.