Assessment of efficacy of [11C]-MeAIB PET/CT as a biomarker of the system A amino acid transport: Comparison with [18F]-FDG and MRI in the patients with prostate cancer

Objectives Although [18F]FDG PET is established as one of the first choice imaging modalities in the diagnosis of malignancies, there are several problems to solve in clinical practice, especially in urological field. The aim of this study was to evaluate the clinical usefulness of α-[N-methyl-11C]-methylaminoisobutyric acid (MeAIB), a highly selective substrate of the system A amino acid transport, in the diagnosis of prostate cancers, compared with FDG and MRI.

Methods Eighteen cases (age: 67.2+/-5.8y.o.) with prostate cancer (PC) who received total prostatectomy were included. We performed preoperative whole body static PET/CT scan twice using FDG and MeAIB on each day. Qualitative analysis and quantitative analysis was performed by two well-experienced physicians and by SUVmax, respectively. MRI was also performed and diffusion-weighted image (DWI) were analyzed.

Results Final diagnosis was 5 unilateral and 13 bilateral PCs (Stage I: n=3, II: n=9, III: n=5, IV: n=1). In quantitative analysis, MeAIB uptake in PC was relatively lower (SUVmax=3.4+/-1.9) than FDG uptake (4.0+/-2.7). Sensitivity of each modality was MeAIB: 11/18, FDG: 8/18, and DWI: 11/18 cases. MeAIB detected two cases with negative DWI, while DWI detected two cases with negative MeAIB. In Stage I-II (n=12), all modalities showed low sensitivity (less than 50%), while in Stage III-IV (n=6), MeAIB and DWI showed higher sensitivity (5/6 and 6/6 cases, respectively). In cases with larger tumor volume (>1cm3), MeAIB and DWI showed high sensitivity (10/12), while MeAIB and DWI showed low sensitivity (1/6) in cases with smaller tumor volume (<1cm3).

Conclusions MeAIB-PET/CT was useful in the diagnosis of PC. MeAIB showed higher sensitivity than FDG and showed complementary role with DWI of MRI