Imaging and response criteria in gliomas

Cerebrospinal Fluid Liquid Biopsies in the Evaluation of Adult Gliomas

PURPOSE OF REVIEW

This review aims to discuss recent research regarding the biomolecules explored in liquid biopsies and their potential clinical uses for adult-type diffuse gliomas.

RECENT FINDINGS

Evaluation of tumor biomolecules via cerebrospinal fluid (CSF) is an emerging technology in neuro-oncology. Studies to date have already identified various circulating tumor DNA, extracellular vesicle, micro-messenger RNA and protein biomarkers of interest. These biomarkers show potential to assist in multiple avenues of central nervous system (CNS) tumor evaluation, including tumor differentiation and diagnosis, treatment selection, response assessment, detection of tumor progression, and prognosis. In addition, CSF liquid biopsies have the potential to better characterize tumor heterogeneity compared to conventional tissue collection and CNS imaging. Current imaging modalities are not sufficient to establish a definitive glioma diagnosis and repeated tissue sampling via conventional biopsy is risky, therefore, there is a great need to improve non-invasive and minimally invasive sampling methods. CSF liquid biopsies represent a promising, minimally invasive adjunct to current approaches which can provide diagnostic and prognostic information as well as aid in response assessment.

18F-DOPA PET/CT in brain tumors: impact on multidisciplinary brain tumor board decisions

PURPOSE

This study aimed to assess the therapeutic impact and diagnostic accuracy of ¹⁸F-DOPA PET/CT in patients with glioblastoma or brain metastases.

METHODS

Patients with histologically proven glioblastoma or brain metastases were prospectively included in this monocentric clinical trial (IMOTEP). Patients were included either due to a clinical suspicion of relapse or to assess residual tumor infiltration after treatment. Multimodality brain MRI and ¹⁸F-DOPA PET were performed. Patients' data were discussed during a Multidisciplinary Neuro-oncology Tumor Board (MNTB) meeting. The discussion was first based on clinical and MRI data, and an initial diagnosis and treatment plan were proposed. Secondly, a new discussion was conducted based on the overall imaging results, including ¹⁸F-DOPA PET. A second diagnosis and therapeutic plan were proposed. A retrospective and definitive diagnosis was obtained after a 3-month follow-up and considered as the reference standard.

RESULTS

One hundred six cases were prospectively investigated by the MNTB. All patients with brain metastases (N = 41) had a clinical suspicion of recurrence. The addition of ¹⁸F-DOPA PET data changed the diagnosis and treatment plan in 39.0% and 17.1% of patients' cases, respectively. Concerning patients with a suspicion of recurrent glioblastoma (N = 12), the implementation of ¹⁸F-DOPA PET changed the diagnosis and treatment plan in 33.3% of cases. In patients evaluated to assess residual glioblastoma infiltration after treatment (N = 53), ¹⁸F-DOPA PET data had a lower impact with only 5.7% (3/53) of diagnostic changes and 3.8% (2/53) of therapeutic plan changes. The definitive reference diagnosis was available in 98/106 patients. For patients with tumor recurrence suspicion, the adjunction of ¹⁸F-DOPA PET increased the Younden's index from 0.44 to 0.53 in brain metastases and from 0.2 to 1.0 in glioblastoma, reflecting an increase in diagnostic accuracy.

CONCLUSION

¹⁸F-DOPA PET has a significant impact on the management of patients with a suspicion of brain tumor recurrence, either glioblastoma or brain metastases, but a low impact when used to evaluate the residual glioblastoma infiltration after a first-line radio-chemotherapy or second-line bevacizumab.

Advanced neuroimaging in the clinic: critical appraisal of the evidence base

The shortage of high-quality systematic reviews in the field of radiology limits evidence-based integration of imaging methods into clinical practice and may perpetuate misconceptions regarding the efficacy and appropriateness of imaging techniques for specific applications. Diffusion tensor imaging for patients with mild traumatic brain injury (DTI-mTBI) and dynamic susceptibility contrast MRI for patients with glioma (DSC-glioma) are applications of quantitative neuroimaging, which similarly detect manifestations of disease where conventional neuroimaging techniques cannot. We performed a critical appraisal of reviews, based on the current evidence-based medicine methodology, addressing the ability of DTI-mTBI and DSC-glioma to (a) detect brain abnormalities and/or (b) predict clinical outcomes. 23 reviews of DTI-mTBI and 26 reviews of DSC-glioma met criteria for inclusion. All reviews addressed detection of brain abnormalities, whereas 12 DTI-mTBI reviews and 22 DSC-glioma reviews addressed prediction of a clinical outcome. All reviews were assessed using a critical appraisal worksheet consisting of 19 yes/no questions. Reviews were graded according to the total number of positive responses and the 2011 Oxford Centre for evidence-based medicine levels of evidence criteria. Reviews addressing DTI-mTBI detection had moderate quality, while those addressing DSC-glioma were of low quality. Reviews addressing prediction of outcomes for both applications were of low quality. Five DTI-mTBI reviews, but only one review of DSC-glioma met criteria for classification as a meta-analysis/systematic/quantitative review.

Lessons from anti-vascular endothelial growth factor and anti-vascular endothelial growth factor receptor trials in patients with glioblastoma

Treatment of glioblastoma (GBM), the most common primary malignant brain tumor in adults, remains a significant unmet need in oncology. Historically, cytotoxic treatments provided little durable benefit, and tumors recurred within several months. This has spurred a substantial research effort to establish more effective therapies for both newly diagnosed and recurrent GBM. In this context, antiangiogenic therapy emerged as a promising treatment strategy because GBMs are highly vascular tumors. In particular, GBMs overexpress vascular endothelial growth factor (VEGF), a proangiogenic cytokine. Indeed, many studies have demonstrated promising radiographic response rates, delayed tumor progression, and a relatively safe profile for anti-VEGF agents. However, randomized phase III trials conducted to date have failed to show an overall survival benefit for antiangiogenic agents alone or in combination with chemoradiotherapy. These results indicate that antiangiogenic agents may not be beneficial in unselected populations of patients with GBM. Unfortunately, biomarker development has lagged behind in the process of drug development, and no validated biomarker exists for patient stratification. However, hypothesis-generating data from phase II trials that reveal an association between increased perfusion and/or oxygenation (ie, consequences of vascular normalization) and survival suggest that early imaging biomarkers could help identify the subset of patients who most likely will benefit from anti-VEGF agents. In this article, we discuss the lessons learned from the trials conducted to date and how we could potentially use recent advances in GBM biology and imaging to improve outcomes of patients with GBM who receive antiangiogenic therapy.

Assessment of temozolomide action encapsulated in chitosan and polymer nanostructures on glioblastoma cell lines

Purpose : Glioblastoma multiforme (GBM) remains one of the most devastating diseases known to mankind and affects more than 17,000 patients in the United States alone every year. This malignancy infiltrates the brain early in its course and makes complete neurosurgical resection almost impossible. Recent years have brought significant advances in tumor biology. Many cancers, including gliomas, appear to be supported by cells with stemlike properties. Nanoparticles are excellent candidates to serve as delivery vectors of drugs or biologically active molecules because of their unique chemical and physical properties that result in specific transportation and deposition of such agents in specific organs and tissues..

In the current study we have investigated the in vitro action of nanostructural systems (temozolomide encapsulated in chitosan and polymer nanostructures) on high-grade gliomaderived cancer stem cells (CSCs), with the intention of developing a new therapy to treat specific brain tumors with increased efficacy and minimal toxicity. In vitro cytotoxicity and apoptosis measurements indicated that the drug/vector combination facilitated the ability of the alkylating drug TMZ to alter the resistance of these cancer stem cells, suggesting a new chemotherapy strategy even for patients diagnosed with inoperable or recurrent malignant gliomas

Methods : At the National Institute for R & D of Isotopic and Molecular Technologies form Cluj Napoca were synthesized three types of nanostructures chitosan-TMZ, TMZ-chitosan-PEG (polyethylene glycol), TMZ-chitosan-PPG (polypropylene glycol). Three type of cell lines (Glioma-derived stem, HFL and HUVEC) were treated with the 3 types of nanostructures and the survival rate of the cells was compare to standard therapy (TMZ).

Results : The results showed a reduction in the rate of survival of the tumor cells. Cell proliferation assays clearly demonstrate the differences betweenconventional chemotherapy (TMZ) and temozolomide encapsulated in chitosan and polymer nanostructures.

Conclusion: Nanostructures like chitosan, PEG, PPG are useful as vectors for drugs transport. Despite combined therapy (surgery, radiotherapy, chemotherapy), currently median patient survival is reduced. The key to improving life expectancy could be an effective therapy targeted, customized for each case. An increasingly important role will be new methods of treatment such as immunotherapy, gene therapy or nanotherapy.

Low incidence of pseudoprogression by imaging in newly diagnosed glioblastoma patients treated with cediranib in combination with chemoradiation

BACKGROUND

Chemoradiation (CRT) can significantly modify the radiographic appearance of malignant gliomas, especially within the immediate post-CRT period. Pseudoprogression (PsP) is an increasingly recognized phenomenon in this setting, and is thought to be secondary to increased permeability as a byproduct of the complex process of radiation-induced tissue injury, possibly enhanced by temozolomide. We sought to determine whether the addition of a vascular endothelial growth factor (VEGF) signaling inhibitor (cediranib) to conventional CRT had an impact on the frequency of PsP, by comparing two groups of patients with newly diagnosed glioblastoma before, during, and after CRT.

METHODS

All patients underwent serial magnetic resonance imaging as part of institutional review board-approved clinical studies. Eleven patients in the control group received only chemoradiation, whereas 29 patients in the study group received chemoradiation and cediranib until disease progression or toxicity. Response assessment was defined according to Response Assessment in Neuro-Oncology criteria, and patients with enlarging lesions were classified into true tumor progressions (TTP) or PsP, based on serial radiographic follow-up.

RESULTS

Two patients in the study group (7%) showed signs of apparent early tumor progression, and both were subsequently classified as TTP. Six patients in the control group (54%) showed signs of apparent early tumor progression, and three were subsequently classified as TTP and three as PsP. The frequency of PsP was significantly higher in the control group.

CONCLUSION

Administration of a VEGF inhibitor during and after CRT modifies the expression of PsP by imaging.

PET in the clinical management of glioma: evidence map

OBJECTIVE

Several studies have assessed PET to complement the anatomic information obtained from other imaging modalities in various clinical contexts for the management of glioma. We constructed an evidence map of clinical evidence on the use of PET in glioma and identified research gaps.

MATERIALS AND METHODS

We searched PubMed and Scopus (from inception through June 30, 2011) to identify studies assessing the use of PET for glioma regardless of setting of care or indication. We extracted test objectives, study characteristics, and phases of diagnostic evidence and then assessed research diversity and temporal trends in the literature. We excluded studies assessing only technical feasibility and optimization of PET.

RESULTS

A total of 129 studies were considered eligible; the number of articles published annually has greatly increased over time (p for trend < 0.001). Most studies (n = 118, 91%) assessed diagnostic or prognostic performance; fewer studies reported on the impact of PET on diagnostic thinking (n = 4, 3%), therapeutic decisions (n = 4, 3%), or patient-relevant clinical outcomes (n = 3; 2%). Fluorine-18 FDG (n = 73, 57%) or (11)C-methionine (n = 44, 34%) were the two most commonly evaluated PET tracers. Pretherapy assessment (n = 72, 56%) and monitoring of treatment response (n = 48, 37%) were the most common settings of test use assessed in the research studies.

CONCLUSION

More primary studies, particularly studies of newer tracers focusing on biopsy or treatment planning, are needed to better characterize the role of PET in specific contexts.

Bevacizumab in high-grade gliomas: a review of its uses, toxicity assessment, and future treatment challenges

High-grade gliomas continue to have dismal prognosis despite advances made in understanding the molecular genetics, signaling pathways, cytoskeletal dynamics, and the role of stem cells in gliomagenesis. Conventional treatment approaches, including surgery, radiotherapy, and cytotoxic chemotherapy, have been used with limited success. Therapeutic advances using molecular targeted therapy, immunotherapy, and others such as dietary treatments have not been able to halt tumor progression and disease-related death. High-grade gliomas (World Health Organization grades III/IV) are histologically characterized by cellular and nuclear atypia, neoangiogenesis, and necrosis. The expression of vascular endothelial growth factor, a molecular mediator, plays a key role in vascular proliferation and tumor survival. Targeting vascular endothelial growth factor has demonstrated promising results, with improved quality of life and progression-free survival. Bevacizumab, a humanized monoclonal antibody to vascular endothelial growth factor, is approved by the Food and Drug Administration as a single agent in recurrent glioblastoma and is associated with manageable toxicity. This review discusses the efficacy, practical aspects, and response assessment challenges with the use of bevacizumab in the treatment of high-grade gliomas.

Surgical resection of malignant gliomas-role in optimizing patient outcome

Malignant gliomas represent one of the most devastating human diseases. Primary treatment of these tumours involves surgery to achieve tumour debulking, followed by a multimodal regimen of radiotherapy and chemotherapy. Survival time in patients with malignant glioma has modestly increased in recent years owing to advances in surgical and intraoperative imaging techniques, as well as the systematic implementation of randomized trial-based protocols and biomarker-based stratification of patients. The role and importance of several clinical and molecular factors-such as age, Karnofsky score, and genetic and epigenetic status-that have predictive value with regard to postsurgical outcome has also been identified. By contrast, the effect of the extent of glioma resection on patient outcome has received little attention, with an 'all or nothing' approach to tumour removal still taken in surgical practice. Recent studies, however, reveal that maximal possible cytoreduction without incurring neurological deficits has critical prognostic value for patient outcome and survival. Here, we evaluate state-of-the-art surgical procedures that are used in management of malignant glioma, with a focus on assessment criteria and value of tumour reduction. We highlight key surgical factors that enable optimization of adjuvant treatment to enhance patient quality of life and improve life expectancy.

Impact of 3,4-dihydroxy-6-18F-fluoro-L-phenylalanine PET/CT on managing patients with brain tumors: the referring physician's perspective

We investigated the impact of (18)F-DOPA brain PET/CT on the clinical management of patients with known or suspected brain tumors.

METHODS

A prospective survey of referring physicians was conducted. A pre-PET questionnaire inquired about indication, tumor histology or grade, level of suspicion for tumor recurrence, and planned management. Early post-PET questionnaires asked referring physicians to categorize PET findings as negative, equivocal, or positive; assessed the level of suspicion for primary or recurrent brain tumor; and recorded intended management changes prompted by PET findings. A late follow-up questionnaire 6 mo after the scan aimed at determining patient outcome (recurrence, survival). In addition, all referring physicians were contacted to determine whether management changes intended after (18)F-DOPA PET/CT were implemented.

RESULTS

Fifty-eight consecutive patients were included. The clinical suspicion for recurrence increased in 33%, remained unchanged in 50%, and decreased in 17% of patients after adding the PET/CT result to the available diagnostic data. The late post-PET questionnaire confirmed recurrence in 26 patients whereas 32 had stable disease or remained disease-free. (18)F-DOPA PET/CT resulted in intended management changes in 41% of patients. Changes in intended management from wait and watch to chemotherapy (6 patients [25%]) and from chemotherapy to wait and watch (4 patients [17%]) occurred most frequently. Clinical follow-up revealed that 75% of intended treatment changes were implemented.

CONCLUSION

(18)F-DOPA PET/CT changed the intended management of 41% of patients with brain tumors, and intended management changes were implemented in 75% of these. These changes suggest a potentially important clinical role of imaging amino acid transport in the management of brain tumor patients.

Pseudoprogression: relevance with respect to treatment of high-grade gliomas

The post-treatment imaging assessment of high-grade gliomas remains challenging notwithstanding the increased utilization of advanced MRI and PET imaging. Several post-treatment imaging entities are recognized including: late-delayed radiation injury, including radionecrosis mimicking tumor progression; early-delayed (within 6 months of temozolomide-based chemoradiation) post-treatment radiographic changes, herein referred to as pseudoprogression (the subject of this review); early post-treatment changes following local glioma therapy (i.e. biodegradable BCNU wafer implantation or stereotactic radiotherapy); and pseudoresponse, seen following treatment with angiogenic inhibition based therapy such as bevacizumab. A literature review searched specifically for "pseudoprogression" within the last 5 years (2005-2010). Approximately 24 recent papers were identified and reviewed in detail. Eight small population-based studies demonstrate 26-58% (median 49%) of glioblastoma patients treated with chemoradiotherapy manifest early disease progression at first post-radiotherapy imaging. Patients with early radiographic disease progression continued on planned therapy, and a median of 38% (range 28-66%) showed radiographic improvement or stabilization and were defined retrospectively as manifesting pseudoprogression. In conclusion, pseudoprogression is a frequent early post-treatment imaging change that at present is not easily differentiated from tumor progression by anatomic or physiologic brain imaging. Consequently, an operational definition of pseudoprogression has been adopted by the Response Assessment in Neuro-Oncology Working Group wherein either the index (i.e. target) lesion stabilizes or diminishes in size on continued post-radiation (temozolomide) therapy as determined by follow-up radiologic imaging.