Thalamo-Basal Ganglia connectivity in postmenopausal women receiving estrogen therapy.

Cumulative data on the effects of estrogen therapy (ET) on brain function in postmenopausal women suggests that ET influences cerebral metabolism and may protect against age-related declines in various domains of cognitive function. The beneficial cognitive effects of ET may relate to its modulation of the thalamic-striatum cholinergic and dopaminergic systems, as the activity of both neurotransmitter systems in the thalamus appears to be positively influenced by estrogen. In the current study, we attempted to evaluated regional cerebral brain metabolism utilizing [18F]-fluorodeoxyglucose positron emission tomography in 11 healthy recently-postmenopausal women on ET (ET+) in comparison to 11 recently-postmenopausal and ET-naïve women (ET-) in order to assess the effects of ET on cholinergic and dopaminergic system regulation. Results showed thalamo-basal ganglia connectivity among ET+ women but not among ET- women. The presence of connectivity in the thalamo-striatal pathway in recently postmenopausal women suggests estrogen effects in preserving integrity of the cholinergic and dopaminergic systems. The results also suggest that ET initiated at or near the menopausal transition may modulate brain aging by mediating complex sensory-motor functions.

Cerebral metabolic patterns in untreated postmenopausal women with major depressive disorder.

Cerebral metabolic rates were assessed using [(18)F]-fluorodeoxyglucose positron emission tomography in six naturally postmenopausal women with untreated unipolar depression and 11 matched controls. All subjects were hormone therapy-naive and medication-free. Findings include hypermetabolism in the middle frontal gyrus and Broca regions, and hypometabolism in the pons among depressed compared with non-depressed women.

Prospective randomized trial to assess effects of continuing hormone therapy on cerebral function in postmenopausal women at risk for dementia.

UNLABELLED: The objective of this study was to examine the effects of estrogen-based hormone therapy (HT) on regional cerebral metabolism in postmenopausal women (mean age = 58, SD = 5) at risk for development of dementia. The prospective clinical trial design included pre- and post-intervention neuroimaging of women randomized to continue (HT+) or discontinue (HT-) therapy following an average of 10 years of use. The primary outcome measure was change in brain metabolism during the subsequent two years, as assessed with fluorodeoxyglucose-18 positron emission tomography (FDG-PET). Longitudinal FDG-PET data were available for 45 study completers. Results showed that women randomized to continue HT experienced relative preservation of frontal and parietal cortical metabolism, compared with women randomized to discontinue HT. Women who discontinued 17-ß estradiol (17ßE)-based HT, as well as women who continued conjugated equine estrogen (CEE)-based HT, exhibited significant decline in metabolism of the precuneus/posterior cingulate cortical (PCC) area. Significant decline in PCC metabolism was additionally seen in women taking concurrent progestins (with either 17ßE or CEE). Together, these findings suggest that among postmenopausal subjects at risk for developing dementia, regional cerebral cortical metabolism is relatively preserved for at least two years in women randomized to continue HT, compared with women randomized to discontinue HT. In addition, continuing unopposed 17ßE therapy is associated specifically with preservation of metabolism in PCC, known to undergo the most significant decline in the earliest stages of Alzheimer's disease. TRIAL REGISTRATION: ClinicalTrials.gov NCT00097058.

Treatment response evaluation using 18F-FDOPA PET in patients with recurrent malignant glioma on bevacizumab therapy.

PURPOSE: This study compares the value of 3,4-dihydroxy-6-[(18)F]-fluoro-l-phenylalanine ((18)F-FDOPA) positron emission tomography (PET) and MRI in assessing outcome during antiangiogenic treatment in patients with recurrent high-grade gliomas. EXPERIMENTAL DESIGN: Thirty patients were prospectively studied with (18)F-FDOPA PET scans immediately before, and two and six weeks after start of bevacizumab therapy. (18)F-FDOPA metabolic tumor volumes (MTV) as well as max and mean standardized uptake values (SUV) within this MTV were obtained. MRI treatment response was assessed at six weeks. The predictive ability of (18)F-FDOPA PET and MRI response assessment were evaluated with regard to progression-free survival (PFS) and overall survival (OS). RESULTS: A total of 30, 28, and 24 (18)F-FDOPA PET scans at baseline, two weeks, and six weeks, were available for analysis, respectively. (18)F-FDOPA PET SUVs as well as their changes through therapy were not predictive of outcome. However, MTV parameters such as MTV changes were highly prognostic. Interestingly, absolute MTV at the first follow up scan provides the most significant prediction for increased OS (P < 0.0001) as well as PFS (P = 0.001). This surprising result was scrutinized with cross-validation and simulation analysis. Responders based on (18)F-FDOPA PET data survived 3.5 times longer (12.1 months vs. 3.5 months, median OS, P < 0.001) than nonresponders (17 patients vs. 11 patients, respectively). In comparison, responders based on MRI data lived 1.5 times longer (11.4 months vs 7.7 months, P = 0.03) than nonresponders (22 patients vs. 7 patients, respectively). CONCLUSIONS: (18)F-FDOPA PET identifies treatment responders to antiangiogenic therapy as early as two weeks after treatment initiation.

The effect of aromatase inhibition on the cognitive function of older patients with breast cancer.

INTRODUCTION: This study evaluated the association between aromatase inhibitor (AI) therapy and cognitive function (over a 6-month period) in a cohort of patients aged ≥ 60 years compared with an age-matched healthy control group, and it evaluated changes in regional cerebral metabolism as measured by positron emission tomography (PET) scans of the brain done in a subset of the patient cohort. PATIENTS AND METHODS: Thirty-five patients (32 evaluable) and 35 healthy controls were recruited to this study. Patients with breast cancer completed a neuropsychological battery, self-reported memory questionnaire, and geriatric assessment before initiation of AI therapy and again 6 months later. Age-matched healthy control participants completed the same assessments at the same time points as the patient group. RESULTS: No significant decline in cognitive function was seen among individuals receiving an AI from pretreatment to 6 months later compared with healthy controls. In the PET cohort over the same period, both standardized volume of interest and statistical parametric mapping analyses detected specific changes in metabolic activity between baseline and follow-up uniquely in the AI patients, most significantly in the medial temporal lobes. CONCLUSION: Although patients undergoing AI treatment had few changes in neuropsychological performance compared with healthy controls over a 6-month period, regionally specific changes in cerebral metabolic activity were identified during this interval in the patient group. Additional longitudinal follow-up is needed to understand the potential clinical implications of these findings.

A pilot study of the effects of meditation on regional brain metabolism in distressed dementia caregivers.

AIMS: Caregiver distress can affect mood and cognition. Meditation can be used to reduce stress. This pilot study explored whether yogic meditation could change regional cerebral metabolism in distressed caregivers. METHODS: Nine dementia caregivers were randomized to undergo meditation training compared with relaxation for 12 min per day for 8 weeks. Caregivers received neuropsychiatric assessments and brain FDG-PET scans at baseline and postintervention. RESULTS: The groups did not differ on measures of mood, mental and physical health, and burden at baseline and follow-up. When comparing the regional cerebral metabolism between groups, significant differences over time were found in the bilateral cerebellum (p < 0.0005), right inferior lateral anterior temporal (p < 0.0005), right inferior frontal (p = 0.001), left superior frontal (p = 0.001), left associative visual (p = 0.002) and right posterior cingulate (p = 0.002) cortices. CONCLUSION: Meditation practice in distressed caregivers resulted in different patterns of regional cerebral metabolism from relaxation. These pilot results should be replicated in a larger study.

3'-deoxy-3'-18F-fluorothymidine PET and MRI for early survival predictions in patients with recurrent malignant glioma treated with bevacizumab.

UNLABELLED: With the dismal prognosis for malignant glioma patients, survival predictions become key elements in patient management. This study compares the value of 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) PET and MRI for early outcome predictions in patients with recurrent malignant glioma on bevacizumab therapy. METHODS: Thirty patients treated with bevacizumab combination therapy underwent (18)F-FLT PET immediately before and at 2 and 6 wk after the start of treatment. A metabolic treatment response was defined as a decrease of equal to or greater than 25% in tumor (18)F-FLT uptake (standardized uptake values) from baseline using receiver-operating-characteristic analysis. MRI treatment response was assessed at 6 wk according to the Response Assessment in Neurooncology criteria. (18)F-FLT responses at different times were compared with MRI response and correlated with progression-free survival and overall survival using Kaplan-Meier analysis. Metabolic response based on (18)F-FLT was further compared with other outcome predictors using Cox regression analysis. RESULTS: Early and late changes in tumor (18)F-FLT uptake were more predictive of overall survival than MRI criteria (P < 0.001 and P = 0.01, respectively). (18)F-FLT uptake changes were also predictive of progression-free survival (P < 0.001). The median overall survival for responders was 3.3 times longer than for nonresponders based on (18)F-FLT PET criteria (12.5 vs. 3.8 mo, P < 0.001) but only 1.4 times longer using MRI assessment (12.9 vs. 9.0 mo, P = 0.05). On the basis of the 6-wk (18)F-FLT PET response, there were 16 responders (53%) and 14 nonresponders (47%), whereas MRI identified 9 responders (7 partial response, 2 complete response, 31%) and 20 nonresponders (13 stable disease, 7 progressive disease, 69%). In 7 of the 8 discrepant cases between MRI and PET, (18)F-FLT PET was able to demonstrate response earlier than MRI. Among various outcome predictors, multivariate analysis identified (18)F-FLT PET changes at 6 wk as the strongest independent survival predictor (P < 0.001; hazard ratio, 10.051). CONCLUSION: Changes in tumor (18)F-FLT uptake were highly predictive of progression-free and overall survival in patients with recurrent malignant glioma on bevacizumab therapy. (18)F-FLT PET seems to be more predictive than MRI for early treatment response.

Differences in regional brain metabolism associated with specific formulations of hormone therapy in postmenopausal women at risk for AD.

Differential cerebral metabolic effects of various hormone therapy formulations, and their associations with cognitive status, remain to be established. The principal aim of the current study was to assess relationships between regional cerebral metabolism and estrogen-based hormone therapies. Postmenopausal women (n=53) at elevated risk for Alzheimer's disease (AD) were on estrogen-containing hormone therapy for at least one year prior to enrollment in a prospective, randomized clinical trial. Subjects underwent an FDG-PET scan, along with neuropsychological, medical, and demographic assessments at time of enrollment, to be repeated one year following randomization to hormone therapy continuation versus discontinuation, and results from analyses of the baseline assessments are reported here. Across all subjects, years of endogenous estrogen exposure correlated most closely with metabolism in right superior frontal gyrus (p<0.0005). Women taking 17ß-estradiol (E) performed three standard deviations higher in verbal memory than women taking conjugated equine estrogen (CEE), and their verbal memory performance positively correlated with metabolism in Wernicke's (p=0.003) and auditory association (p=0.002) areas. Women taking progesterone-plus-estrogen had lower metabolism than women taking unopposed estrogen within the mesial and inferior lateral temporal regions (p<0.0005) and the inferior frontal cortex, contralateral to Broca's area (p<0.0005). In conclusion, particular areas of relatively preserved metabolism were seen in women with more years of endogenous estrogen exposure, as well as in women taking estradiol-based formulations or estrogen therapies unopposed by progesterone, together suggesting regionally specific neuroprotective estrogenic effects.

Correlation of 6-18F-fluoro-L-dopa PET uptake with proliferation and tumor grade in newly diagnosed and recurrent gliomas.

UNLABELLED: 6-(18)F-fluoro-l-dopa ((18)F-FDOPA) measured with PET as a biomarker of amino acid uptake has been investigated in brain tumor imaging. The aims of the current study were to determine whether the degree of (18)F-FDOPA uptake in brain tumors predicted tumor grade and was associated with tumor proliferative activity in newly diagnosed and recurrent gliomas. METHODS: Fifty-nine patients (40 men, 19 women; mean age ± SD, 44.4 ± 12.3 y) with newly diagnosed (n = 22) or recurrent (n = 37) gliomas underwent (18)F-FDOPA PET perioperatively. Tumor tissue was obtained by resection or biopsy in all patients. The tumor grade and Ki-67 proliferation index were obtained by standard pathology assays. Tumor (18)F-FDOPA uptake was quantified by determining various standardized uptake value (SUV) parameters (mean SUV, maximum SUV [SUVmax], mean values of voxels with top 20% SUVs, and tumor-to-normal-brain tissue ratios) that were then correlated with histopathologic grade and Ki-67 proliferation index. RESULTS: Fifty-nine lesions in 59 patients were analyzed. (18)F-FDOPA uptake was significantly higher in high-grade than in low-grade tumors for newly diagnosed tumors (SUVmax, 4.22 ± 1.30 vs. 2.34 ± 1.35, P = 0.005) but not for recurrent tumors that had gone through treatment previously (SUVmax, 3.36 ± 1.26 vs. 2.67 ± 1.18, P = 0.22). An SUVmax threshold of 2.72 differentiated low-grade from high-grade tumors, with a sensitivity and specificity of 85% and 89%, respectively, using receiver-operating-characteristic curve analysis (area under the curve, 0.86). (18)F-FDOPA PET uptake correlated significantly with Ki-67 tumor proliferation index in newly diagnosed tumors (r = 0.66, P = 0.001) but not in recurrent tumors (r = 0.14, P = 0.41). CONCLUSION: (18)F-FDOPA uptake is significantly higher in high-grade than in low-grade tumors in newly diagnosed but not recurrent tumors that had been treated previously. A significant correlation between (18)F-FDOPA uptake and tumor proliferation in newly diagnosed tumors was observed, whereas this correlation was not identified for recurrent tumors. Thus, (18)F-FDOPA PET might serve as a noninvasive marker of tumor grading and might provide a useful surrogate of tumor proliferative activity in newly diagnosed gliomas.

Predicting treatment response of malignant gliomas to bevacizumab and irinotecan by imaging proliferation with [18F] fluorothymidine positron emission tomography: a pilot study.

PURPOSE: Evaluation of treatment effects in malignant brain tumors is challenging because of the lack of reliable response predictors of tumor response. This study examines the predictive value of positron emission tomography (PET) using [18F] fluorothymidine (FLT), an imaging biomarker of cell proliferation, in patients with recurrent malignant gliomas treated with bevacizumab in combination with irinotecan. PATIENTS AND METHODS: Patients with recurrent malignant gliomas treated with biweekly cycles of bevacizumab and irinotecan were prospectively studied with FLT-PET at baseline, after 1 to 2 weeks, and after 6 weeks from start of treatment. A more than 25% reduction in tumor FLT uptake as measured by standardized uptake value was defined as a metabolic response. FLT responses were compared with response as shown by magnetic resonance imaging (MRI) and patient survival. RESULTS: Twenty-one patients were included, and 19 were assessable for metabolic response evaluation with FLT-PET. There were nine responders (47%) and 10 nonresponders (53%). Metabolic responders survived three times as long as nonresponders (10.8 v 3.4 months; P = .003), and tended to have a prolonged progression-free survival (P = .061). Both early and later FLT-PET responses were more significant predictors of overall survival (1 to 2 weeks, P = .006; 6 weeks, P = .002), compared with the MRI responses (P = .060 for both 6-week and best responses). CONCLUSION: FLT-PET as an imaging biomarker seems to be predictive of overall survival in bevacizumab and irinotecan treatment of recurrent gliomas. Whether FLT-PET performed as early as 1 to 2 week after starting treatment is as predictive as the study indicates at 6 weeks warrants further investigation.