Clinical impact of F-18 Flutemetamol (FMM) PET to assess cerebral Aß pathology in patients with various cognitive disorders.

Objectives: Cerebral ß-amyloid (Aß) deposition significantly influences the clinical course not only in patients with suspected Alzheimer’s disease but also in other cognitive disorders. Therefore, accurate assessment of cerebral Aß pathology is necessary , which became possible with recently introduced fluorine-18 positron tracers. The purpose of this study was to investigate the clinical impact of F-18 Flutemetamol (FMM) PET to assess cerebral Aß pathology in patients with various cognitive disorders.

Methods: A total of 39 patients (18M, 21F, 73±13 years old) with various cognitive disorders of unestablished diagnoses (diagnostic confidence level less than 90%) underwent FMM PET to investigate cerebral beta-amyloid depositions. First, participating physicians were blinded to the results of FMM PET and discussed a summary of standard neuropsychological work-up (including conventional medical imaging) of each case to predict cerebral Aß pathology and to achieve a preliminary diagnosis. Second, the preliminary result was compared with the result of FMM PET to investigate its clinical impact. Clinical impact was considered positive when the result of FMM PET required revision of the preliminary neurological diagnosis.

Results: There were 21 patients with dementia (MMSE ≤ 24) and the remaining18 were patients with mild cognitive impairment (MCI). The conventional assessments predicted positive for Aß pathology in 12/21 in dementia, and 6/18 in MCI, while FMM-PET was positive for 4 and 12 patients, respectively. Clinical impact of FMM-PET was greater in MCI (8/18 = 44%) than in dementia (6/21 = 29%). The conventional assessments tended to over-diagnose Aß pathology particularly in MCI patients (Tables).

Conclusions: FMM-PET influenced neurological diagnosis in 36% (14/39) of patients with cognitive disorders. The impact was particularly higher in MCI patients, which may warrant the use of this technique for an accurate early diagnosis.