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.

Objective: L-3-[(18)F]-fluoro-α-methyl tyrosine ((18)F-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. (18)F-FAMT PET/CT, fluorine-18-fluorodeoxyglucose ((18)F-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).
Methods: Twenty-seven patients with OSCC on the upper or lower alveolar ridge underwent staging by MRI, (18)F-FDG PET/CT and (18)F-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, (18)F-FDG PET/CT and (18)F-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.
Results: As the sensitivity of (18)F-FDG PET/CT was highest (100 %) among that of MRI (95 %) and (18)F-FAMT PET/CT (90 %), the specificity of (18)F-FAMT PET/CT was highest (85.7 %) among that of MRI (57 %) and (18)F-FDG PET/CT (14.3 %). The size of pathological tumor was accorded with that detected by (18)F-FAMT PET/CT and was smaller than that detected by (18)F-FDG PET/CT (P < 0.01). Significant difference was not found between (18)F-FAMT PET tumor volume and pathological tumor volume.
Conclusions: (18)F-FAMT PET/CT was useful and more specific than MRI or (18)F-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.