Title: P4‐282: Prognostic significance of Florbetapir (18F‐Florbetapir) PET imaging for future cognitive performance in recently diagnosed MCI: Final results from a 3‐year multicenter longitudinal trial
Abstract: 52 particpants with recently diagnosed mild cognitive impairment (rMCI: CDR 0.5, MMSE>24, <1 year since diagnosis) consented to return for a clinical evaluation and psychometric testing including ADAScog 11, CDR sum of boxes (CDR-SOB), digit symbol substitution (DSS), Wechsler logical Memory, and category verbal fluency) 18 and 36 months after PET imaging with 10 mCi (370 MBq) of florbetapir. Three nuclear medicine physicians rated each florbetapir image as amyloid positive (Aβ+) or negative (Aβ-). ANCOVA (Age, baseline score adjusted) compared LOCF 3-year change in ADAScog (primary analysis) and other psychometric tests as a function of PET amyloid status. Of 47 rMCI subjects with post baseline data, 17 (36%) were classified as Aβ+ by majority visual read. ADAScog performance worsened by 5.66 (SE 1.47) points from baseline to year 3 (or last post baseline timepoint) in Aβ+ subjects while improving by 0.71(SE 1.09) points in Aβ- subjects (P=0.0014). 8/17 Aβ+ (4147%) vs 3/30 Aβ- (10%) subjects showed a clinically significant 4 point ADAScog decline over the follow-up period (p=0.0094). Baseline amyloid status was also significant predictor of worsening at 3 years in CDR-SOB (p=0.0223), DSST (p=0.0002), MMSE (p=0.0148), and verbal fluency (p=0.0051). In a stepwise regression model with Age, Education, ApoE allele and baseline psychometric test score as possible risk factors, Aβ status remained a significant predictor (p<0.05) for ADAScog, CDR-SOB, MMSE, and verbal fluency. These differences were evident despite the fact that 12/17 Aβ+ vs only 7/30 Aβ- eMCI received treatment with ACHE-I or memantine during the follow-up period. Amyloid positive ratings of florbetapir PET scans were associated with increased rate of progressive cognitive decline.