Efficacy of [¹⁸F]flutemetamol in the Japanese population

Objectives Efficacy of [¹⁸F]flutemetamol as a brain β-amyloid imaging agent has been validated on Caucasians, but little has been reported on Japanese. Positivity and degree of amyloid deposit were investigated using [¹⁸F]flutemetamol-based PET scans on Japanese subjects with probable Alzheimer’s disease (pAD), amnestic mild cognitive impairment (aMCI) and healthy volunteers (HVs), together with inter-reader agreement and test-retest reproducibility.

Methods 20 subjects with pAD, 20 subjects with aMCI and 25 HVs underwent a 30min PET scan starting 90min post injection of 185MBq of [¹⁸F]flutemetamol. Additional 5 pAD subjects underwent two PET scans less than 4 weeks apart, to evaluate test-retest variability. Blinded visual image reads by independent board-certified readers were compared with the subject’s clinical diagnoses and with composite cortical standardized uptake value ratios (SUVR) using cerebellar cortex as the reference region. Inter-reader agreement was assessed for 5 Japanese and for 5 non-Japanese readers.

Results Clinical diagnoses and the blinded reads were highly associated, with positive rate of 23/25 for pAD, 10/20 for aMCI and 1/25 for HV. SUVR (mean±SD) was 2.05±0.42 for pAD, 1.61±0.30 for aMCI, and 1.20 ±0.09 for HV. There was good agreement between SUVR and blinded reads, and the PET images allowed differentiation between pAD subjects and HVs. The kappa statistic for inter-reader agreement was 0.94 and 0.96 for 5 Japanese readers and for 5 non-Japanese readers, respectively. The mean test-retest variability of SUVR ranged from 1.85% to 2.27% across all cortical regions. Test-retest agreement of the blinded reads was 100% for all readers.

Conclusions [¹⁸F]flutemetamol is a robust tracer with qualitative and quantitative reproducibility and is useful for in vivo detection of increased brain β-amyloid load for the Japanese population.

Research Support This study is the phase-II clinical trial (GE067-017) sponsored by GE Healthcare.