Diagnostic usefulness of ¹⁸F-FAMT PET and L-type amino acid transporter 1 (LAT1) expression in oral squamous cell carcinoma

Purpose: l-[3-¹⁸F]-α-Methyltyrosine (¹⁸F-FAMT) was developed as an amino acid tracer for PET imaging to provide better specificity than 2-[¹⁸F]fluoro-2-deoxy-d-glucose (¹⁸F-FDG) PET for cancer diagnosis. We investigated the diagnostic usefulness of ¹⁸F-FAMT in oral squamous cell carcinoma (OSCC). The correlation between tumour uptake of ¹⁸F-FAMT and L-type amino acid transporter 1 (LAT1) expression was determined. Methods: The study group comprised 68 OSCC patients who underwent both ¹⁸F-FAMT and ¹⁸F-FDG PET. Resected tumour sections were stained by immunohistochemistry for LAT1, CD98 and Ki-67, and microvessel density was determined in terms of CD34 and p53 expression. Results: The sensitivity of primary tumour detection by ¹⁸F-FAMT and ¹⁸F-FDG PET was 98 % and 100 %, respectively. The sensitivity, specificity and accuracy of ¹⁸F-FAMT PET for detecting malignant lymph nodes were 68 %, 99 % and 97 %, respectively, and equivalent values for ¹⁸F-FDG PET were 84 %, 94 % and 94 %, respectively. The specificity and accuracy of ¹⁸F-FAMT were significantly higher than those of ¹⁸F-FDG. The uptake of ¹⁸F-FAMT was significantly correlated with LAT1 expression, cell proliferation and advanced stage. The expression of LAT1 in OSCC cells was closely correlated with CD98 levels, cell proliferation and angiogenesis. Conclusion: ¹⁸F-FAMT PET showed higher specificity for detecting malignant lesions than ¹⁸F-FDG PET. The uptake of ¹⁸F-FAMT by OSCC cells can be determined by the presence of LAT1 expression and tumour cell proliferation.