Longitudinal Changes in Serum Glucose Levels are Associated with Metabolic Changes in Alzheimer's Disease Related Brain Regions.

BACKGROUND: The association between longitudinal changes in serum glucose level and longitudinal changes in [18F] Fluorodeoxyglucose-PET (FDG PET) measurements of Alzheimer's disease (AD) risk are unknown. OBJECTIVE: To investigate whether variation in serum glucose levels across time are associated with changes in FDG PET measurements of cerebral metabolic rate for glucose (rCMRgl) in brain regions preferentially affected by Alzheimer's disease (AD). METHODS: Participants are a subset of a prospective cohort study investigating FDG PET, apolipoprotein E (APOE) ɛ4, and risk for AD which includes data from baseline, interim, and follow up visits over 4.4±1.0-years. An automated brain-mapping algorithm was utilized to characterize and compare associations between longitudinal changes in serum glucose levels and longitudinal changes in rCMRgl. RESULTS: This study included 80 adults aged 61.5±5 years, including 38 carriers and 42 non-carriers of the APOE ɛ4 allele. Longitudinal increases in serum glucose levels were associated with longitudinal CMRgl decline in the vicinity of parietotemporal, precuneus/posterior cingulate, and prefrontal brain regions preferentially affected by AD (p < 0.05, corrected for multiple comparisons). Findings remained significant when controlled for APOE ɛ4 status and baseline and advancing age. CONCLUSIONS: Additional studies are needed to clarify and confirm the relationship between longitudinal changes in peripheral glucose and FDG PET measurements of AD risk. Future findings will set the stage on the use of FDG PET in the evaluation of possible interventions that target risk factors for the development of AD.

Positron emission tomography in three children with pleomorphic xanthoastrocytoma.

The pleomorphic xanthoastrocytoma is generally considered a low-grade neoplasm with favorable prognosis. These tumors, however, can demonstrate primary anaplastic features, undergo malignant transformation, disseminate, or progress with poor outcome. Currently, there are no histologic or clinical features that reliably predict recurrent tumor or tumor progression. We report three children with confirmed pleomorphic xanthoastrocytoma who were studied with positron emission tomography (PET) using [18F]fluorodeoxyglucose (FDG) coregistered with magnetic resonance imaging. One patient had decreased FDG metabolism and, despite a gross total resection and benign pathology, had early local recurrence. Subsequent to a second surgical resection and radiation therapy, he has remained stable for 8 years. One patient with significant FDG uptake had gross total resection of an anaplastic pleomorphic xanthoastrocytoma. Follow-up FDG studies showed no abnormal metabolic activity, and he has been stable without adjuvant treatment for 5 years. The last patient had intermediate FDG uptake and a moderate-grade pleomorphic xanthoastrocytoma by histopathology. She showed early tumor progression with spinal metastases. Following a near-total resection of the recurrent intracranial lesion and neuroaxis radiation, she has been stable for 4 years. Although there are still no reliable prognostic indicators for pleomorphic xanthoastrocytoma, PET with FDG correlates with histopathology, and increased uptake may be a marker for more malignant or aggressive tumors. The extent of surgical resection in regard to prognosis in our limited study is unclear but appears helpful in the anaplastic pleomorphic xanthoastrocytoma case. Adjuvant radiation therapy also may benefit certain patients. Further PET studies are warranted in this group of tumors.