An attentional and working memory theory of hallucination vulnerability in frontotemporal dementia

The rate and prevalence of hallucinations in behavioural variant frontotemporal dementia is well established. The mechanisms for underlying vulnerability however are the least well described in FTD compared with other neuropsychiatric conditions, despite the presence of these features significantly complicating the diagnostic process. As such, this present study aimed to provide a detailed characterization of the neural, cognitive and behavioural profile associated with a predisposition to hallucinatory experiences in behavioural variant frontotemporal dementia. In total, 153 patients with behavioural variant frontotemporal dementia were recruited sequentially for this study. A group of patients with well characterized hallucinations and good-quality volumetric MRI scans (n = 23) were genetically and demographically matched to a group without hallucinations (n = 23) and a healthy control cohort (n = 23). All patients were assessed at their initial visit by means of a detailed clinical interview, a comprehensive battery of neuropsychological tests and MRI. Data were analysed according to three levels: (i) the relationship between neural structures, cognition, behaviour and hallucinations in behavioural variant frontotemporal dementia; (ii) the impact of the C9orf72 expansion; and (iii) hallucination subtype on expression of hallucinations. Basic and complex attentional (including divided attention and working memory) and visual function measures differed between groups (all P < 0.001) with hallucinators demonstrating poorer performance, along with evidence of structural changes centred on the prefrontal cortex, caudate and cerebellum (corrected for False Discovery Rate at P < 0.05 with a cluster threshold of 100 contiguous voxels). Attentional processes were also implicated in C9orf72 carriers with hallucinations with structural changes selectively involving the thalamus. Patients with visual hallucinations in isolation showed a similar pattern with emphasis on cerebellar atrophy. Our findings provided novel insights that attentional and visual function subsystems and related distributed brain structures are implicated in the generation of hallucinations in behavioural variant frontotemporal dementia, that dissociate across C9orf72, sporadic behavioural variant frontotemporal dementia and for the visual subtype of hallucinations. This loading on attentional and working memory measures is in line with current mechanistic models of hallucinations that frequently suggest a failure of integration of cognitive and perceptual processes. We therefore propose a novel cognitive and neural model for hallucination predisposition in behavioural variant frontotemporal dementia that aligns with a transdiagnostic model for hallucinations across neurodegeneration and psychiatry.

Understanding the effects of serotonin in the brain through its role in the gastrointestinal tract

The neuromodulatory arousal system imbues the nervous system with the flexibility and robustness required to facilitate adaptive behaviour. While there are well-understood mechanisms linking dopamine, noradrenaline and acetylcholine to distinct behavioural states, similar conclusions have not been as readily available for serotonin. Fascinatingly, despite clear links between serotonergic function and cognitive capacities as diverse as reward processing, exploration, and the psychedelic experience, over 95% of the serotonin in the body is released in the gastrointestinal tract, where it controls digestive muscle contractions (peristalsis). Here, we argue that framing neural serotonin as a rostral extension of the gastrointestinal serotonergic system dissolves much of the mystery associated with the central serotonergic system. Specifically, we outline that central serotonin activity mimics the effects of a digestion/satiety circuit mediated by hypothalamic control over descending serotonergic nuclei in the brainstem. We review commonalities and differences between these two circuits, with a focus on the heterogeneous expression of different classes of serotonin receptors in the brain. Much in the way that serotonin-induced peristalsis facilitates the work of digestion, serotonergic influences over cognition can be reframed as performing the work of cognition. Extending this analogy, we argue that the central serotonergic system allows the brain to arbitrate between different cognitive modes as a function of serotonergic tone: low activity facilitates cognitive automaticity, whereas higher activity helps to identify flexible solutions to problems, particularly if and when the initial responses fail. This perspective sheds light on otherwise disparate capacities mediated by serotonin, and also helps to understand why there are such pervasive links between serotonergic pathology and the symptoms of psychiatric disorders.

Locus coeruleus integrity and the effect of atomoxetine on response inhibition in Parkinson's disease

Cognitive decline is a common feature of Parkinson's disease, and many of these cognitive deficits fail to respond to dopaminergic therapy. Therefore, targeting other neuromodulatory systems represents an important therapeutic strategy. Among these, the locus coeruleus-noradrenaline system has been extensively implicated in response inhibition deficits. Restoring noradrenaline levels using the noradrenergic reuptake inhibitor atomoxetine can improve response inhibition in some patients with Parkinson's disease, but there is considerable heterogeneity in treatment response. Accurately predicting the patients who would benefit from therapies targeting this neurotransmitter system remains a critical goal, in order to design the necessary clinical trials with stratified patient selection to establish the therapeutic potential of atomoxetine. Here, we test the hypothesis that integrity of the noradrenergic locus coeruleus explains the variation in improvement of response inhibition following atomoxetine. In a double-blind placebo-controlled randomized crossover design, 19 patients with Parkinson's disease completed an acute psychopharmacological challenge with 40 mg of oral atomoxetine or placebo. A stop-signal task was used to measure response inhibition, with stop-signal reaction times obtained through hierarchical Bayesian estimation of an ex-Gaussian race model. Twenty-six control subjects completed the same task without undergoing the drug manipulation. In a separate session, patients and controls underwent ultra-high field 7 T imaging of the locus coeruleus using a neuromelanin-sensitive magnetization transfer sequence. The principal result was that atomoxetine improved stop-signal reaction times in those patients with lower locus coeruleus integrity. This was in the context of a general impairment in response inhibition, as patients on placebo had longer stop-signal reaction times compared to controls. We also found that the caudal portion of the locus coeruleus showed the largest neuromelanin signal decrease in the patients compared to controls. Our results highlight a link between the integrity of the noradrenergic locus coeruleus and response inhibition in patients with Parkinson's disease. Furthermore, they demonstrate the importance of baseline noradrenergic state in determining the response to atomoxetine. We suggest that locus coeruleus neuromelanin imaging offers a marker of noradrenergic capacity that could be used to stratify patients in trials of noradrenergic therapy and to ultimately inform personalized treatment approaches.

Impaired sensory evidence accumulation and network function in Lewy body dementia

Deficits in attention underpin many of the cognitive and neuropsychiatric features of Lewy body dementia. These attention-related symptoms remain difficult to treat and there are many gaps in our understanding of their neurobiology. An improved understanding of attention-related impairments can be achieved via mathematical modelling approaches, which identify cognitive parameters to provide an intermediate level between observed behavioural data and its underlying neural correlate. Here, we apply this approach to identify the role of impaired sensory evidence accumulation in the attention deficits that characterize Lewy body dementia. In 31 people with Lewy body dementia (including 13 Parkinson's disease dementia and 18 dementia with Lewy bodies cases), 16 people with Alzheimer's disease, and 23 healthy controls, we administered an attention task whilst they underwent functional 3 T MRI. Using hierarchical Bayesian estimation of a drift-diffusion model, we decomposed task performance into drift rate and decision boundary parameters. We tested the hypothesis that the drift rate-a measure of the quality of sensory evidence accumulation-is specifically impaired in Lewy body dementia, compared to Alzheimer's disease. We further explored whether trial-by-trial variations in the drift rate related to activity within the default and dorsal attention networks, to determine whether altered activity in these networks was associated with slowed drift rates in Lewy body dementia. Our results revealed slower drift rates in the Lewy body dementia compared to the Alzheimer's disease group, whereas the patient groups were equivalent for their decision boundaries. The patient groups were reduced relative to controls for both parameters. This highlights sensory evidence accumulation deficits as a key feature that distinguishes attention impairments in Lewy body dementia, consistent with impaired ability to efficiently process information from the environment to guide behaviour. We also found that the drift rate was strongly related to activity in the dorsal attention network across all three groups, whereas the Lewy body dementia group showed a divergent relationship relative to the Alzheimer's disease and control groups for the default network, consistent with altered default network modulation being associated with impaired evidence accumulation. Together, our findings reveal impaired sensory evidence accumulation as a specific marker of attention problems in Lewy body dementia, which may relate to large-scale network abnormalities. By identifying impairments in a specific sub-process of attention, these findings will inform future exploratory and intervention studies that aim to understand and treat attention-related symptoms that are a key feature of Lewy body dementia.

GABA and glutamate deficits from frontotemporal lobar degeneration are associated with disinhibition

Behavioural disinhibition is a common feature of the syndromes associated with frontotemporal lobar degeneration (FTLD). It is associated with high morbidity and lacks proven symptomatic treatments. A potential therapeutic strategy is to correct the neurotransmitter deficits associated with FTLD, thereby improving behaviour. Reductions in the neurotransmitters glutamate and GABA correlate with impulsive behaviour in several neuropsychiatric diseases and there is post-mortem evidence of their deficit in FTLD. Here, we tested the hypothesis that prefrontal glutamate and GABA levels are reduced by FTLD in vivo, and that their deficit is associated with impaired response inhibition. Thirty-three participants with a syndrome associated with FTLD (15 patients with behavioural variant frontotemporal dementia and 18 with progressive supranuclear palsy, including both Richardson's syndrome and progressive supranuclear palsy-frontal subtypes) and 20 healthy control subjects were included. Participants undertook ultra-high field (7 T) magnetic resonance spectroscopy and a stop-signal task of response inhibition. We measured glutamate and GABA levels using semi-LASER magnetic resonance spectroscopy in the right inferior frontal gyrus, because of its strong association with response inhibition, and in the primary visual cortex, as a control region. The stop-signal reaction time was calculated using an ex-Gaussian Bayesian model. Participants with frontotemporal dementia and progressive supranuclear palsy had impaired response inhibition, with longer stop-signal reaction times compared with controls. GABA concentration was reduced in patients versus controls in the right inferior frontal gyrus, but not the occipital lobe. There was no group-wise difference in partial volume corrected glutamate concentration between patients and controls. Both GABA and glutamate concentrations in the inferior frontal gyrus correlated inversely with stop-signal reaction time, indicating greater impulsivity in proportion to the loss of each neurotransmitter. We conclude that the glutamatergic and GABAergic deficits in the frontal lobe are potential targets for symptomatic drug treatment of frontotemporal dementia and progressive supranuclear palsy.

P14.124 EORTC 1709/CCTG CE.8: A phase III trial of marizomib in combination with standard temozolomide-based radiochemotherapy versus standard temozolomide-based radiochemotherapy alone in patients with newly diagnosed glioblastoma

BACKGROUND

The standard of care for patients with newly diagnosed glioblastoma includes maximal debulking surgery followed by radiotherapy (RT), and concomitant as well as maintenance therapy with the alkylating agent, temozolomide (TMZ). However, the prognosis remains poor and novel treatment strategies are urgently needed. Targeting the proteasome has been considered a promising anti-cancer approach for several years. Marizomib is a novel, irreversible and pan-proteasome inhibitor, which crosses the blood-brain barrier and has been assessed in phase I trials in patients with newly diagnosed or recurrent glioblastoma.

MATERIAL AND METHODS

EORTC 1709/CCTG CE.8 is a randomized, controlled, open label phase III superiority trial. Patients with histologically confirmed newly diagnosed glioblastoma and a performance status >70 are eligible. Patients are randomized in a 1:1 ratio to receive standard of care (TMZ/RT→TMZ) alone or TMZ/RT→TMZ plus marizomib. The study aims at enrolling 750 patients. Stratification factors include study site, age, performance status and extent of resection. The primary objective of this trial is to compare overall survival in patients receiving marizomib in addition to standard of care with those receiving standard treatment only. The testing strategy specifies the determination of this objective in the intent-to-treat population as well as the subgroup of patients with MGMT-unmethylated tumors. Secondary endpoints include progression-free survival, safety, neurocognitive function and quality of life. A translational research program has been set up. The study will be activated at approximately 50 EORTC sites across Europe, 25 sites in Canada and additional sites in the US. Patient recruitment started in June 2018 and as of April 29, 2019, a total of 164 patients have been randomized. An update on the enrolment status will be provided at the EANO meeting. ClinicalTrials.gov Identifier: NCT03345095

Dopamine depletion alters macroscopic network dynamics in Parkinson's disease

Parkinson's disease is primarily characterized by diminished dopaminergic function; however, the impact of these impairments on large-scale brain dynamics remains unclear. It has been difficult to disentangle the direct effects of Parkinson's disease from compensatory changes that reconfigure the functional signature of the whole brain network. To examine the causal role of dopamine depletion in network-level topology, we investigated time-varying network structure in 37 individuals with idiopathic Parkinson's disease, both ON and OFF dopamine replacement therapy, along with 50 age-matched, healthy control subjects using resting state functional MRI. By tracking dynamic network-level topology, we found that the Parkinson's disease OFF state was associated with greater network-level integration than in the ON state. The extent of integration in the OFF state inversely correlated with motor symptom severity, suggesting that a shift toward a more integrated network topology may be a compensatory mechanism associated with preserved motor function in the dopamine depleted OFF state. Furthermore, we were able to demonstrate that measures of both cognitive and brain reserve (i.e. premorbid intelligence and whole brain grey matter volume) had a positive relationship with the relative increase in network integration observed in the dopaminergic OFF state. This suggests that each of these factors plays an important role in promoting network integration in the dopaminergic OFF state. Our findings provide a mechanistic basis for understanding the Parkinson's disease OFF state and provide a further conceptual link with network-level reconfiguration. Together, our results highlight the mechanisms responsible for pathological and compensatory change in Parkinson's disease.

Changes in structural network topology correlate with severity of hallucinatory behavior in Parkinson's disease

Inefficient integration between bottom-up visual input and higher order visual processing regions is implicated in visual hallucinations in Parkinson's disease (PD). Here, we investigated white matter contributions to this perceptual imbalance hypothesis. Twenty-nine PD patients were assessed for hallucinatory behavior. Hallucination severity was correlated to connectivity strength of the network using the network-based statistic approach. The results showed that hallucination severity was associated with reduced connectivity within a subnetwork that included the majority of the diverse club. This network showed overall greater between-module scores compared with nodes not associated with hallucination severity. Reduced between-module connectivity in the lateral occipital cortex, insula, and pars orbitalis and decreased within-module connectivity in the prefrontal, somatosensory, and primary visual cortices were associated with hallucination severity. Conversely, hallucination severity was associated with increased between- and within-module connectivity in the orbitofrontal and temporal cortex, as well as regions comprising the dorsal attentional and default mode network. These results suggest that hallucination severity is associated with marked alterations in structural network topology with changes in participation along the perceptual hierarchy. This may result in the inefficient transfer of information that gives rise to hallucinations in PD.

Comorbidity and overall survival (OS) in cetuximab-treated patients with advanced colorectal cancer (ACRC)—Results from NCIC CTG CO.17: A phase III trial of cetuximab versus best supportive care (BSC)

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Background: The interplay between comorbidity, age and performance status (PS) as predictors of outcome in ACRC is not well described. We examined these factors as predictors of treatment toxicity and outcome in cetuximab-treated patients with ACRC. Methods: Comorbidity was independently evaluated by 2 physicians using the Charlson Comorbidity Index (CCI), a previously validated measure of comorbidity based on the presence or absence of index medical conditions weighted according to their affect on mortality. CCI score was correlated with demographic data (age, gender), PS, site of primary, time from diagnosis to randomization, body mass index, hemoglobin, alkaline phosphatase (ALP), lactate dehydrogenase (LDH), creatinine clearance, K-ras status and OS. Results: 572 patients were included. 41% were ≥65 years and 25% had comorbidities at randomization. CCI score was 1 in 21% and ≥ 2 in 4%. In multivariate analysis (MVA) of all covariates, only older age (≥65 years) was associated with greater comorbidity (p=0.005). OS was different among 3 comorbidity groups (CCI score 0, 1, ≥ 2) in univariate analysis (median OS 4.9 vs 5.9 vs 4.8 months;, logrank p=0.04) but not in MVA. Conversely, lower PS remained associated with better OS in MVA (HR 1.96 for PS=2 vs. PS=0, p<0.0001). Age was not associated with OS (p=0.11). Other factors significantly associated with OS in MVA included time from diagnosis to randomization, LDH, ALP, hemoglobin, Kras status and cetuximab treatment. In the BSC arm, comorbidity was not associated with OS in MVA (HR 0.83 CCI 1 vs. CCI0, p=0.26 and HR 0.90 for CCI2 vs. CCI0, p=0.78) suggesting comorbidity is not prognostic in this setting. Patients with higher CCI score had a nonsignificant trend toward greater treatment effects. Patients ≥65 years had less gr≥3 vomiting (1.8 vs 7.9%, p=0.034) but more dyspnea (24.5 vs 11.2%, p=0.005). Patients with higher CCI scores had less vomiting (p=0.008) but more non-neutropenic infection (p=0.012). Conclusions: In this clinical trial, comorbidity and age were not independent predictors of survival, highlighting the difference between comorbidity and PS.

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Quality of life in patients with advanced colorectal cancer treated with cetuximab: Results of the NCIC CTG and AGITG CO.17 trial

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Background: Cetuximab prolongs survival in pretreated advanced colorectal cancer (CRC) patients (pts). For these pts, the effect of palliative treatment on quality of life (QOL) is also an important outcome. Methods: CO.17 was a randomized controlled trial (n=572) of cetuximab combined with best supportive care (BSC) vs BSC alone in pts with pretreated epidermal growth factor receptor-positive advanced CRC. Primary endpoint was survival. QOL was a secondary endpoint using the EORTC QLQ-C30 at baseline, 4, 8, 16, and 24 weeks (wks). Primary endpoint for QOL compared physical function (PF) and global health status (Global) mean changes from baseline to 8 and 16 wks using Wilcoxon test. Negative change scores denote worsening QOL. The proportion of pts in either arm with at least a 10 unit deterioration at 8 and 16 wks from baseline was compared using Fischer’s exact test. Kaplan-Meier estimates and logrank tests on median time to definitive QOL deterioration, defined as at least a 10 unit deterioration in PF or Global, were evaluated. Exploratory analyses of all other scale and symptom change scores at 8 and 16 wks were also performed. Results: Compliance rates for QOL questionnaires was high at baseline, 94% each arm, but did drop off over time: 73% vs 60% at week 8 and 60% vs 39% at week 16 for cetuximab vs BSC, respectively. PF change scores at 8 wks were -3.9 for cetuximab vs -8.6 for BSC (p=.046); at 16 wks -5.9 vs -12.5 (p=.027). Global change scores were -0.5 vs -7.1 (p=.008) and -3.6 vs -15.2 (p=.008) at 8 and 16 wks respectively. The proportion of pts with deteriorating PF was 25% for cetuximab vs 35% for BSC at 8 wks (p=.051) and 30 vs 43% at 16 wks (p=.069). Deteriorating Global was seen in 23 vs 38% at 8 wks (p=.004) and 31 vs 49% at 16 wks (p=.0011). Time to PF deterioration was 5.4 months [95% CI 3.8–5.7] for cetuximab vs 3.7 months [2.0–3.9] for BSC (p=.022). Time to Global deterioration was 5.4 [3.9–5.7] vs 3.7 months [2.1–3.9] (p=.062). Exploratory analyses of all other scale and symptom change scores at 8 and 16 wks showed all differences of p<.05 also favored cetuximab. Conclusions: Cetuximab provides palliation in pretreated pts with advanced CRC, delaying deterioration in QOL as well as improving survival.

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The use of warfarin for venous thromboembolism (VTE): Practical problems for patients and resource implications for an oncology unit

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Background: Recent evidence has suggested improved efficacy with low molecular weight heparin (LMWH) over oral coumarins for the treatment of cancer patients with VTE. Oral anticoagulants present multiple practical problems for patients undergoing chemotherapy, including side-effects, disruption of anticoagulation for invasive procedures, multiple drug interactions and multiplicity of patient visits. To assess the practice implications of these issues, a review was carried out in a busy medical oncology unit. Methods: A retrospective review of all patients treated with the coumarin derivative, warfarin for VTE during the last year was undertaken. Patients on prophylactic warfarin for central venous devices were excluded. Computerised laboratory records were used to identify patients. Patients were assessed for adverse events and therapeutic efficacy. The extra volume of work involved in monitoring blood tests and treating complications was quantified. Results: 55 patients with VTE were treated with warfarin from 07/01/04 to 06/30/05. The majority (73%) had metastatic carcinoma. 21 invasive interventions required disruption of anticoagulation. 90% of these were in patients with metastatic disease. Each patient was subtherapeutic (International normalised ratio <2.0) for a mean of 30.7 days (25% of mean duration of anticoagulation). There were 8 admissions for haemorrhage. Nine patients died on warfarin, 8 of whom had metastatic disease. In one patient with significant cardiac comorbidity warfarin therapy contributed to early death. No patterns of drug interactions were identified. A total of 1,369 coagulation tests were performed. There were 382 extra blood test visits, representing 26% of all day ward blood visits. On treatment, 13 patients (24%) were changed from warfarin therapy to LMWH. In 4 patients there was progression of VTE. In 9 patients, all with metastatic disease LMWH was substituted to qualitatively improve patient care by minimising hospital visits and facilitating home based care. Conclusions: This study identifies the high rate of treatment change to LMWH and quantifies the extra resource utilization with coumarin therapy. This supports the increased primary use of LMWH in selected cancer patients.

No significant financial relationships to disclose.