Complementary roles of tumour specific PET tracer 18F-FAMT to 18F-FDG PET/CT for the assessment of bone metastasis

The usefulness of F-18-FDG PET/CT for bone metastasis evaluation has already been established. The amino acid PET tracer [F-18]-3-fluoro-alpha-methyl tyrosine (F-18-FAMT) has been reported to be highly specific for malignancy. We evaluated the additional value of F-18-FAMT PET/CT to complement F-18-FDG PET/CT in the evaluation of bone metastasis. This retrospective study included 21 patients with bone metastases of various cancers who had undergone both F-18-FDG and F-18-FAMT PET/CT within 1 month of each other. F-18-FDG-avid bone lesions suspicious for malignancy were carefully selected based on the cut-off value for malignancy, and the SUVmax of the F-18-FAMT in the corresponding lesions were evaluated. A total of 72 F-18-FDG-positive bone lesions suspected to be metastases in the 21 patients were used as the reference standard. F-18-FAMT uptake was found in 87.5 % of the lesions. In the lesions of lung cancer origin, the uptake of the two tracers showed a good correlation (40 lesions, r = 0.68, P < 0.01). Bone metastatic lesions of oesophageal cancer showed the highest average of F-18-FAMT uptake. Bone metastatic lesions of squamous cell carcinoma showed higher F-18-FAMT uptake than those of adenocarcinoma. No significant difference in F-18-FAMT uptake was seen between osteoblastic and osteolytic bone metastatic lesions. The usefulness of F-18-FAMT PET/CT for bone metastasis detection regardless of the lesion phenotype was demonstrated. The fact that F-18-FAMT uptake was confirmed by F-18-FDG uptake suggests that F-18-FAMT PET/CT has the potential to complement F-18-FDG PET/CT for the detection of bone metastases.