18F-FAMT in patients with multiple myeloma: clinical utility compared to 18F-FDG

Objective

l-[3-¹⁸F]-alpha-methyltyrosine (¹⁸F-FAMT) is an amino-acid tracer for positron emission tomography (PET), with uptake related to overexpression of L-type amino-acid transporter 1 and proliferative activity in tumour cells. This study evaluated the diagnostic performance of ¹⁸F-FAMT PET compared with 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) PET in patients with multiple myeloma (MM).

Methods

Eleven patients with MM (newly diagnosed, n?=?3; relapsed after treatment, n?=?8) underwent whole-body ¹⁸F-FAMT and ¹⁸F-FDG PET within a 2-week interval. Magnetic resonance imaging (MRI) of the spine was also performed to assess patterns of bone marrow infiltration. Tracer uptake was semi-quantitatively evaluated using maximal standardized uptake value (SUV_max). Mean SUV was also determined for normal bone marrow and the aortic arch as mediastinal background SUV to calculate lesion-to-bone marrow (L/B) and lesion-to-mediastinum (L/M) ratios, respectively. Those values were statistically compared using Student??s t test.

Results

In 8 patients showing focal infiltration on MRI, 34 FDG-avid bone lesions were identified, with each showing increased FAMT uptake. Mean SUV_max and L/B ratio of FDG (3.1?±?1.2 and 3.3?±?1.9, respectively) were significantly higher than those of FAMT (2.0?±?1.0 and 2.6?±?1.1, respectively; p?p?=?0.3).

Conclusions

Clear ¹⁸F-FAMT PET uptake was seen in most ¹⁸F-FDG-avid lesions among patients with MM, and an equivalent semi-quantitative value was obtained using L/M ratio. Our preliminary data suggest that ¹⁸F-FAMT PET provides a useful imaging modality for detecting active myelomatous lesions.