Philip C De Witt Hamer

Philip C De Witt Hamer
Amsterdam University Medical Center | VUmc · Department of Neurosurgery

Professor

About

217
Publications
28,152
Reads
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4,780
Citations
Additional affiliations
September 2007 - present
Amsterdam University Medical Center
Position
  • neurosurgeon
January 2002 - December 2009
Universiteit van Amsterdam

Publications

Publications (217)
Article
Full-text available
Intraoperative brain stimulation mapping reduces permanent postoperative deficits and extends tumor removal in resective surgery for glioma patients. Successful functional mapping is assumed to depend on the surgical team's expertise. In this study, glioma resection results are quantified and compared using a novel approach, so-called resection pro...
Article
Full-text available
Surgery for infiltrative gliomas aims to balance tumor removal with preservation of functional integrity. The usefulness of intraoperative stimulation mapping (ISM) has not been addressed in randomized trials. This study addresses glioma surgery outcome on the basis of a meta-analysis of observational studies. A systematic search retrieved 90 repor...
Article
Full-text available
WEE1 kinase is a key molecule in maintaining G₂-cell-cycle checkpoint arrest for premitotic DNA repair. Whereas normal cells repair damaged DNA during G₁-arrest, cancer cells often have a deficient G₁-arrest and largely depend on G₂-arrest. The molecular switch for the G₂-M transition is held by WEE1 and is pushed forward by CDC25. WEE1 is overexpr...
Article
It is unclear why exactly gliomas show preferential occurrence in certain brain areas. Increased spiking activity around gliomas leads to faster tumour growth in animal models, while higher non-invasively measured brain activity is related to shorter survival in patients. However, it is unknown how regional intrinsic brain activity, as measured in...
Article
Full-text available
Cancer patients benefit from early tumor detection since treatment outcomes are more favorable for less advanced cancers. Platelets are involved in cancer progression and are considered a promising biosource for cancer detection, as they alter their RNA content upon local and systemic cues. We show that tumor-educated platelet (TEP) RNA-based blood...
Article
Full-text available
Background New technologies developed to improve survival outcomes for glioblastoma (GBM) continue to have limited success. Recently, image-guided dose painting (DP) radiotherapy has emerged as a promising strategy to increase local control rates. In this study, we evaluate the practical application of a multiparametric MRI model of glioma infiltra...
Article
Background While patients with diffuse low-grade glioma (LGG) often survive for years, there is a risk of tumour progression which may impact on patients’ long-term health-related quality of life (HRQOL) and neurocognitive functioning (NCF). We present a follow-up of LGG patients and their informal caregivers (T3) who took part in our previous HRQO...
Preprint
Background Even though fatigue is one of the most prevalent and burdensome symptoms in patients with glioma, its etiology and determinants are still poorly understood. We aimed to identify which demographic, tumor- and treatment-related characteristics and patient-reported outcome measures (PROMs) are associated with or are predictors of fatigue in...
Article
Full-text available
Background. People with gliomas need specialized neurosurgical, neuro-oncological, psycho-oncological, and neuropsychological care. The role of language and cognitive recovery and rehabilitation in patients’ well-being and resumption of work is crucial, but there are no clear guidelines for the ideal timing and character of assessments and interven...
Article
Full-text available
For patients suffering from brain tumor, prognosis estimation and treatment decisions are made by a multidisciplinary team based on a set of preoperative MR scans. Currently, the lack of standardized and automatic methods for tumor detection and generation of clinical reports, incorporating a wide range of tumor characteristics, represents a major...
Preprint
Many patients with glioma, primary brain tumors, suffer from poorly understood executive functioning deficits before and/or after tumor resection. We aimed to test whether frontoparietal network centrality of multilayer networks, which allow for integration across multiple frequencies, relates to and predicts executive functioning in glioma patient...
Article
Full-text available
Background: Cannabinoids have been suggested to alleviate frequently experienced symptoms of reduced mental well-being such as anxiety and depression. Mental well-being is an important subdomain of health-related quality of life (HRQoL). Reducing symptoms and maintaining HRQoL are particularly important in malignant primary brain tumor patients, as...
Article
Full-text available
Background Fatigue is the most frequent and burdensome symptom of patients with diffuse glioma. It is closely linked to decreased health-related quality of life and symptoms such as depression and sleep disturbances. Currently, there is no evidence-based treatment that targets severe fatigue in patients with brain tumours. Cognitive behavioural the...
Article
Full-text available
Management of gliomas requires an invasive treatment strategy, including extensive surgical resection. The objective of the neurosurgeon is to maximize tumor removal while preserving healthy brain tissue. However, the lack of a clear tumor boundary hampers the neurosurgeon’s ability to accurately detect and resect infiltrating tumor tissue. Nonline...
Article
Background: Accurate characterization of glioma is crucial for clinical decision making. A delineation of the tumor is also desirable in the initial decision stages but is time-consuming. Previously, deep learning methods have been developed that can either non-invasively predict the genetic or histological features of glioma, or that can automati...
Article
Full-text available
Background People with gliomas need specialized neurosurgical, neuro-oncological, psycho-oncological, and neuropsychological care. The role of language and cognitive recovery and rehabilitation in patients’ well-being and resumption of work is crucial, but there are no clear guidelines for the ideal timing and character of assessments and intervent...
Article
Full-text available
Background and purpose: Glioblastoma (GBM) patients have a dismal prognosis. Tumours typically recur within months of surgical resection and post-operative chemoradiation. Multiparametric magnetic resonance imaging (mpMRI) biomarkers promise to improve GBM outcomes by identifying likely regions of infiltrative tumour in tumour probability (TP) map...
Article
Full-text available
Background In patients with newly-diagnosed glioblastoma, rapid early progression (REP) refers to tumour regrowth between surgery and postoperative chemoradiotherapy. This systematic review and meta-analysis appraised published data on REP to better characterise and understand it. Methods Systematic searches of MEDLINE, EMBASE and the Cochrane dat...
Preprint
Full-text available
For patients suffering from brain tumor, prognosis estimation and treatment decisions are made by a multidisciplinary team based on a set of preoperative MR scans. Currently, the lack of standardized and automatic methods for tumor detection and generation of clinical reports represents a major hurdle. In this study, we investigate glioblastomas, l...
Article
Objective: Patients with glioblastoma are often scheduled for urgent elective surgery. Currently, the impact of the waiting period until glioblastoma surgery is undetermined. In this national quality registry study, the authors determined the wait times until surgery for patients with glioblastoma, the risk factors associated with wait times, and...
Article
Purpose: Tyrosine kinase inhibitors (TKIs) have poor efficacy in patients with glioblastoma (GBM). Here, we studied whether this is predominantly due to restricted blood-brain barrier penetration or more to biological characteristics of GBM. Experimental design: Tumor drug concentrations of the TKI sunitinib after 2 weeks of preoperative treatme...
Preprint
It is unclear why exactly gliomas show preferential occurrence in certain brain areas. Increased spiking activity around gliomas leads to faster tumor growth in animal models, while higher non-invasively measured brain activity is related to shorter survival in patients. However, it is unknown how regional intrinsic brain activity, as measured in h...
Article
Full-text available
Cancer therapy for both central nervous system (CNS) and non-CNS tumors has been previously associated with transient and long-term cognitive deterioration, commonly referred to as ‘chemo fog’. This therapy-related damage to otherwise normal-appearing brain tissue is reported using post-mortem neuropathological analysis. Although the literature on...
Preprint
Background: Glioma patients experience a multitude of symptoms, impacting health-related quality of life. We aimed to assess frequency and burden of patient-reported symptoms in glioma patients with stable disease and whether patients would consider treatment. We also explored how symptoms co-occur and interact within a network.Methods: Patients ra...
Article
BACKGROUND Patients with low-grade gliomas (LGGs) often survive for many years, yet little is known about patients’ health-related quality of life (HRQOL) in long-term survivorship. We previously investigated HRQOL in LGG patients diagnosed on average 6 years prior to assessment (T1, N=195) with a follow-up in stable patients on average 12 years af...
Article
Full-text available
The neocortex is disproportionately expanded in human compared with mouse1,2, both in its total volume relative to subcortical structures and in the proportion occupied by supragranular layers composed of neurons that selectively make connections within the neocortex and with other telencephalic structures. Single-cell transcriptomic analyses of hu...
Article
Full-text available
Glioma intratumoral heterogeneity enables adaptation to challenging microenvironments and contributes to therapeutic resistance. We integrated 914 single-cell DNA methylomes, 55,284 single-cell transcriptomes and bulk multi-omic profiles across 11 adult IDH mutant or IDH wild-type gliomas to delineate sources of intratumoral heterogeneity. We showe...
Article
OBJECTIVE Awake craniotomies are often characterized by alternating asleep-awake-asleep periods. Preceding the awake phase, patients are weaned from anesthesia and mechanical ventilation. Although clinicians aim to minimize the time to awake for patient safety and operating room efficiency, in some patients, the time to awake exceeds 20 minutes. Th...
Poster
BACKGROUND Over the past years, increasing worldwide attention towards centralization of complex cancer care has been pursued as higher volume centers have shown improved outcomes. Changes in distribution of care and the impact on travel distance in glioblastoma patients have not been determined yet. In this study, we determine trends in distributi...
Poster
BACKGROUND Delay in cancer care may adversely affect emotional distress, treatment outcome and survival. Optimal timings in multidisciplinary glioblastoma care are a matter of debate and clear national guidelines only exist for time to neurosurgery. We evaluated the between-hospital variation in timings to neurosurgery and adjuvant radiotherapy and...
Article
Full-text available
Temporal lobe epilepsy (TLE) patients are at risk of memory deficits, which have been linked to functional network disturbances, particularly of integration of the default mode network (DMN). However, the cellular substrates of functional network integration are unknown. We leverage a unique cross-scale dataset of drug-resistant TLE patients (n = 3...
Article
Full-text available
Non-invasively measured brain activity is related to progression-free survival in glioma patients, suggesting its potential as a marker of glioma progression. We therefore assessed the relationship between brain activity and increasing tumor volumes on routine clinical magnetic resonance imaging (MRI) in glioma patients. Postoperative magnetoenceph...
Article
Full-text available
The left temporal lobe is an integral part of the language system and its cortical structure and function associate with general intelligence. However, whether cortical laminar architecture and cellular properties of this brain area relate to verbal intelligence is unknown. Here, we addressed this using histological analysis and cellular recordings...
Article
Full-text available
For patients with presumed glioblastoma, essential tumor characteristics are determined from preoperative MR images to optimize the treatment strategy. This procedure is time-consuming and subjective, if performed by crude eyeballing or manually. The standardized GSI-RADS aims to provide neurosurgeons with automatic tumor segmentations to extract t...
Article
BACKGROUND Patients with diffuse glioma experience many tumor- and treatment-related symptoms, including fatigue, cognitive deficits, and anxiety. It remains unclear how the frequency and burden of these symptoms change over time and specifically which symptoms patients experience during the stable phase of the disease. We assessed the frequency an...
Article
BACKGROUND Many patients with low-grade gliomas (LGGs) continue to survive for many years, yet little is known about patients’ health-related quality of life (HRQOL) in long-term survivorship. We previously investigated HRQOL in LGG patients diagnosed on average 6 years prior to assessment (T1, N=195) with a follow-up in stable patients on average...
Article
BACKGROUND Glioma patients experience a high symptom burden contributing to poorer quality of life. Symptoms include depression, cognitive impairment, and fatigue and vary throughout the disease. These symptoms are rarely studied from a comprehensive perspective, while their interdependence may be relevant for their development, perpetuation, and u...
Article
BACKGROUND Gliomas are primary brain tumors with a dismal prognosis. Reducing symptoms and maintaining quality of life (QoL) are main treatment aims in glioma patients. Mental well-being is an important subdomain of QoL. Cannabinoids have been suggested to alleviate frequently experienced symptoms of reduced mental well-being such as anxiety or dep...
Article
BACKGROUND Besides early tumour progression, standard first-line radiation with concurrent and adjuvant temozolomide in de novo glioblastoma patients is abrogated frequently by severe haematological toxicity. This leads to treatment delays with unknown effect on efficacy and to more hospital visits with increased disease burden. In the present stud...
Article
Full-text available
Background Regional collaboration and appropriate referral management are crucial in neuro-oncological care. Lack of electronic access to medical records across healthcare organisations impedes interhospital consultation and may lead to incomplete and delayed referrals. To improve referral management, we have established a multidisciplinary Neuro-O...
Article
Full-text available
Awake surgery with cognitive monitoring has increasingly been implemented to preserve brain networks and functionality. More recently, not only surgery in the left but also in the right hemisphere, i.c., the parietal lobe, was associated with potential risk for deficits in cognitive functions, such as cognitive flexibility. In this explorative pilo...
Conference Paper
Glioma intratumoral heterogeneity enables adaptation to challenging microenvironments and contributes to universal therapeutic resistance. Here, we integrated 914 single-cell DNA methylomes, 55,284 single-cell transcriptomes, and bulk multi-omic profiles across 11 adult IDH-mutant or IDH-wild-type gliomas to delineate sources of intratumoral hetero...
Conference Paper
p>Diffuse gliomas are malignant neoplasms originating in the parenchyma of the central nervous system whose cellular origin remains elusive. To determine the cellular and spatiotemporal origin of gliomas, we devised a three-dimensional reconstruction of tumor lineage. We used neuronavigation to acquire eight to twelve image-guided and spatially sep...
Article
OBJECTIVE The aim of glioblastoma surgery is to maximize the extent of resection while preserving functional integrity. Standards are lacking for surgical decision-making, and previous studies indicate treatment variations. These shortcomings reflect the need to evaluate larger populations from different care teams. In this study, the authors used...
Article
Full-text available
Treatment decisions for patients with presumed glioblastoma are based on tumor characteristics available from a preoperative MR scan. Tumor characteristics, including volume, location, and resectability, are often estimated or manually delineated. This process is time consuming and subjective. Hence, comparison across cohorts, trials, or registries...
Article
Full-text available
Diffuse gliomas are infiltrative primary brain tumors with a poor prognosis despite multimodal treatment. Maximum safe resection is recommended whenever feasible. The extent of resection (EOR) is positively correlated with survival. Identification of glioma tissue during surgery is difficult due to its diffuse nature. Therefore, glioma resection is...
Article
Full-text available
Background: Intratumoral heterogeneity is a hallmark of diffuse gliomas. DNA methylation profiling is an emerging approach in the clinical classification of brain tumors. The goal of this study is to investigate the effects of intratumoral heterogeneity on classification confidence. Methods: We used neuronavigation to acquire 133 image-guided an...
Article
Introduction: Glioma patients show increased global brain network clustering relating to poorer cognition and epilepsy. However, it is unclear whether this increase is spatially widespread, localized in the (peri)tumor region only, or decreases with distance from the tumor. Materials and methods: Weighted global and local brain network clusterin...
Article
Full-text available
Background The impact of time-to-surgery on clinical outcome for patients with glioblastoma has not been determined. Any delay in treatment is perceived as detrimental, but guidelines do not specify acceptable timings. In this study we relate the time to glioblastoma surgery with the extent of resection and residual tumor volume, performance change...
Article
Full-text available
Introduction For decisions on glioblastoma surgery, the risk of complications and decline in performance is decisive. In this study, we determine the rate of complications and performance decline after resections and biopsies in a national quality registry, their risk factors and the risk-standardized variation between institutions. Methods Data f...
Preprint
Full-text available
The expansion of supragranular cortical layers is thought to have enabled evolutionary development of human cognition and language. However, whether increased volume of supragranular cortical layers can actually support greater cognitive and language abilities in humans has not been demonstrated. Here, we find that subjects with higher general and...
Preprint
Non-invasively measured brain activity is related to progression-free survival in glioma patients, suggesting its potential as a marker of glioma progression. We therefore assessed the relationship between brain activity and increasing tumor volumes on routine clinical magnetic resonance imaging (MRI) in glioma patients. Postoperative magnetoenceph...
Preprint
Full-text available
Temporal lobe epilepsy patients are heterogeneous regarding cognitive functioning, with predominant risk of memory deficits. Despite major advances within cellular neuroscience, neuroimaging, and neuropsychology, it remains challenging to integrate memory performance with cellular characteristics and brain network topology. In a unique dataset, we...
Article
Full-text available
Functional outcome following glioma surgery is defined as how the patient functions or feels. Functional outcome is a coprimary end point of surgery in patients with diffuse glioma, together with oncological outcome. In this review, we structure the functional outcome measurements following glioma surgery as reported in the last 5 yr. We review var...
Article
Intratumoral heterogeneity is a hallmark of diffuse gliomas and inhibits effective prediction of clinical outcome. To devise a three-dimensional reconstruction of tumor lineage, we used neuronavigation to acquire eight to twelve image-guided and spatially separated stereotactic biopsy samples from 16 adult patients with a diffuse glioma, which we c...
Preprint
Accurate characterization of glioma is crucial for clinical decision making. A delineation of the tumor is also desirable in the initial decision stages but is a time-consuming task. Leveraging the latest GPU capabilities, we developed a single multi-task convolutional neural network that uses the full 3D, structural, pre-operative MRI scans to can...
Article
Full-text available
Tumor-educated platelets (TEPs) are potential biomarkers for cancer diagnostics. We employ TEP-derived RNA panels, determined by swarm intelligence, to detect and monitor glioblastoma. We assessed specificity by comparing the spliced RNA profile of TEPs from glioblastoma patients with multiple sclerosis and brain metastasis patients (validation ser...
Article
Purpose: To improve the robustness of deep learning-based glioblastoma segmentation in a clinical setting with sparsified datasets. Materials and methods: In this retrospective study, preoperative T1-weighted, T2-weighted, T2-weighted fluid-attenuated inversion recovery, and postcontrast T1-weighted MRI from 117 patients (median age, 64 years; i...
Preprint
Full-text available
Glioma intratumoral heterogeneity enables adaptation to challenging microenvironments and contributes to universal therapeutic resistance. Here, we integrated 914 single-cell DNA methylomes, 55,284 single-cell transcriptomes, and bulk multi-omic profiles across 11 adult IDH-mutant or IDH-wild-type gliomas to delineate sources of intratumoral hetero...
Article
Full-text available
To summarize the distribution of glioma location within a patient population, registration of individual MR images to anatomical reference space is required. In this study, we quantified the accuracy of MR image registration to anatomical reference space with linear and non-linear transformations using estimated tumor targets of glioblastoma and lo...
Article
Objective: Decisions in glioblastoma surgery are often guided by presumed eloquence of the tumor location. The authors introduce the "expected residual tumor volume" (eRV) and the "expected resectability index" (eRI) based on previous decisions aggregated in resection probability maps. The diagnostic accuracy of eRV and eRI to predict biopsy decis...