Maintenance Therapy With Tumor-Treating Fields Plus Temozolomide vs Temozolomide Alone for Glioblastoma: A Randomized Clinical Trial

Temozolomide treatment can improve overall survival in aggressive pituitary tumors and pituitary carcinomas

OBJECTIVES

Only few retrospective studies have reported an efficacy rate of temozolomide (TMZ) in pituitary tumors (PT), all around 50%. However, the long-term survival of treated patients is rarely evaluated. We therefore aimed to describe the use of TMZ on PT in clinical practice and evaluate the long-term survival.

DESIGN

Multicenter retrospective study by members of the French Society of Endocrinology.

METHODS

Forty-three patients (14 women) treated with TMZ between 2006 and 2016 were included. Most tumors were corticotroph (n = 23) or lactotroph (n = 13), and 14 were carcinomas. Clinical/pathological characteristics of PT, as well as data from treatment evaluation and from the last follow-up were recorded. A partial response was considered as a decrease in the maximal tumor diameter by more than 30% and/or in the hormonal rate by more than 50% at the end of treatment.

RESULTS

The median treatment duration was 6.5 cycles (range 2-24), using a standard regimen for most and combined radiotherapy for six. Twenty-two patients (51.2%) were considered as responders. Silent tumor at diagnosis was associated with a poor response. The median follow-up after the end of treatment was 16 months (0-72). Overall survival was significantly higher among responders (P = 0.002); however, ten patients relapsed 5 months (0-57) after the end of TMZ treatment, five in whom TMZ was reinitiated without success.

DISCUSSION

Patients in our series showed a 51.2% response rate to TMZ, with an improved survival among responders despite frequent relapses. Our study highlights the high variability and lack of standardization of treatment protocols.

Practice-Changing Abstracts From the 2016 Society for Neuro-Oncology Annual Scientific Meeting

The most relevant practice-changing presentations at the 2016 Society for Neuro-Oncology (SNO) Annual Scientific Meeting revolved around the topic of the new 2016 World Health Organization (WHO) classification of central nervous system (CNS) tumors. The most notable change in this new classification is the introduction of molecular markers into the morphologic classification of diffuse gliomas (isocitrate dehydrogenase [IDH] mutation, 1p19q codeletion, and H3K27M mutation), ependymomas (RELA fusion), medulloblastomas (WNT- and sonic hedgehog-activated), and other embryonal tumors (C19MC amplification), thus allowing for more precise diagnosis of these entities compared with the use of morphologic features alone. Among the clinical trials presented, only one phase III trial evaluating a device therapy for treatment of newly diagnosed glioblastoma (EF14; tumor-treating fields) met prespecified statistical criteria for success, showing a modest benefit in progression-free survival and overall survival in patients without progression after radiation and concurrent temozolomide. Other topics of interest included the spatial and temporal heterogeneity of primary brain tumors and the prevalence of burnout among neuro-oncologists.

Analysis of physical characteristics of Tumor Treating Fields for human glioblastoma

Tumor Treating Fields (TTFields) therapy is an approved treatment that has known clinical efficacy against recurrent and newly diagnosed glioblastoma. However, the distribution of the electric fields and the corresponding pattern of energy deposition in the brain are poorly understood. To evaluate the physical parameters that may influence TTFields, postacquisition MP-RAGE, T1 and T2 MRI sequences from a responder with a right parietal glioblastoma were anatomically segmented and then solved using finite-element method to determine the distribution of the electric fields and rate of energy deposition at the gross tumor volume (GTV) and other intracranial structures. Electric field-volume histograms (EVH) and specific absorption rate-volume histograms (SARVH) were constructed to numerically evaluate the relative and/or absolute magnitude volumetric differences between models. The electric field parameters E_AUC , V_E150 , E_95% , E_50% , and E_20% , as well as the SAR parameters SAR_AUC , V_SAR7.5 , SAR_95% , SAR_50% , and SAR_20% , facilitated comparisons between models derived from various conditions. Specifically, TTFields at the GTV were influenced by the dielectric characteristics of the adjacent tissues as well as the GTV itself, particularly the presence or absence of a necrotic core. The thickness of the cerebrospinal fluid on the convexity of the brain and the geometry of the tumor were also relevant factors. Finally, the position of the arrays also influenced the electric field distribution and rate of energy deposition in the GTV. Using EVH and SARVH, a personalized approach for TTFields treatment can be developed when various patient-related and tumor-related factors are incorporated into the planning procedure.

Prognostic Molecular and Imaging Biomarkers in Primary Glioblastoma

PURPOSE

Several molecular glioma markers (including isocitrate dehydrogenase 1 [IDH1] mutation, amplification of the epidermal growth factor receptor [EGFR], and methylation of the O6-methylguanine-DNA methyltransferase [MGMT] promoter) have been associated with glioblastoma survival. In this study, we examined the association between tumoral amino acid uptake, molecular markers, and overall survival in patients with IDH1 wild-type (primary) glioblastoma.

PATIENTS AND METHODS

Twenty-one patients with newly diagnosed IDH1 wild-type glioblastomas underwent presurgical MRI and PET scanning with alpha[C-11]-L-methyl-tryptophan (AMT). MRI characteristics (T2- and T1-contrast volume), tumoral tryptophan uptake, PET-based metabolic tumor volume, and kinetic variables were correlated with prognostic molecular markers (EGFR and MGMT) and overall survival.

RESULTS

EGFR amplification was associated with lower T1-contrast volume (P = 0.04) as well as lower T1-contrast/T2 volume (P = 0.04) and T1-contrast/PET volume ratios (P = 0.02). Tumors with MGMT promoter methylation showed lower metabolic volume (P = 0.045) and lower tumor/cortex AMT unidirectional uptake ratios than those with unmethylated MGMT promoter (P = 0.009). While neither EGFR amplification nor MGMT promoter methylation was significantly associated with survival, high AMT tumor/cortex uptake ratios on PET were strongly prognostic for longer survival (hazards ratio, 30; P = 0.002). Estimated mean overall survival was 26 months in patients with high versus 8 months in those with low tumoral AMT uptake ratios.

CONCLUSIONS

The results demonstrate specific MRI and amino acid PET imaging characteristics associated with EGFR amplification and MGMT promoter methylation in patients with primary glioblastoma. High tryptophan uptake on PET may identify a subgroup with prolonged survival.

Glioblastoma multiforme (GBM) in the elderly: initial treatment strategy and overall survival

The EORTC trial which solidified the role of external beam radiotherapy (EBRT) plus temozolomide (TMZ) in the management of GBM excluded patients over age 70. Randomized studies of elderly patients showed that hypofractionated EBRT (HFRT) alone or TMZ alone was at least equivalent to conventionally fractionated EBRT (CFRT) alone. We sought to investigate the practice patterns and survival in elderly patients with GBM. We identified patients age 65-90 in the National Cancer Data Base (NCDB) with histologically confirmed GBM from 1998 to 2012 and known chemotherapy and radiotherapy status. We analyzed factors predicting treatment with EBRT alone vs. EBRT plus concurrent single-agent chemotherapy (CRT) using multivariable logistic regression. Similarly, within the EBRT alone cohort we compared CFRT (54-65 Gy at 1.7-2.1 Gy/fraction) to HFRT (34-60 Gy at 2.5-5 Gy/fraction). Multivariable Cox proportional hazards model (MVA) with propensity score adjustment was used to compare survival. A total of 38,862 patients were included. Initial treatments for 1998 versus 2012 were: EBRT alone = 50 versus 10%; CRT = 6 versus 50%; chemo alone = 1.6% (70% single-agent) versus 3.2% (94% single-agent). Among EBRT alone patients, use of HFRT (compared to CFRT) increased from 13 to 41%. Numerous factors predictive for utilization of CRT over EBRT alone and for HFRT over CFRT were identified. Median survival and 1-year overall survival were higher in the CRT versus EBRT alone group at 8.6 months vs. 5.1 months and 36.0 versus 15.7% (p < 0.0005 by log-rank, multivariable HR 0.65 [95% CI = 0.61-0.68, p < 0.0005], multivariable HR with propensity adjustment 0.66 [95% CI = 0.63-0.70, p < 0.0005]). For elderly GBM patients in the United States, CRT is the most common initial treatment and appears to offer a survival advantage over EBRT alone. Adoption of hypofractionation has increased over time but continues to be low.

A Feasibility Study of Personalized Prescription Schemes for Glioblastoma Patients Using a Proliferation and Invasion Glioma Model

Purpose: This study investigates the feasibility of personalizing radiotherapy prescription schemes (treatment margins and fractional doses) for glioblastoma (GBM) patients and their potential benefits using a proliferation and invasion (PI) glioma model on phantoms. Methods and Materials: We propose a strategy to personalize radiotherapy prescription schemes by simulating the proliferation and invasion of the tumor in 2D according to the PI glioma model. We demonstrate the strategy and its potential benefits by presenting virtual cases, where the standard and personalized prescriptions were applied to the tumor. Standard prescription was assumed to deliver 46 Gy in 23 fractions to the initial, gross tumor volume (GTV₁) plus a 2 cm margin and an additional 14 Gy in 7 fractions to the boost GTV₂ plus a 2 cm margin. The virtual cases include the tumors with a moving velocity of 0.029 (slow-move), 0.079 (average-move), and 0.13 (fast-move) mm/day for the gross tumor volume (GTV) with a radius of 1 (small) and 2 (large) cm. For each tumor size and velocity, the margin around GTV₁ and GTV₂ was varied between 0–6 cm and 1–3 cm, respectively. Equivalent uniform dose (EUD) to normal brain was constrained to the EUD value obtained by using the standard prescription. Various linear dose policies, where the fractional dose is linearly decreasing, constant, or increasing, were investigated to estimate the temporal effect of the radiation dose on tumor cell-kills. The goal was to find the combination of margins for GTV₁ and GTV₂ and a linear dose policy, which minimize the tumor cell-surviving fraction (SF) under a normal tissue constraint. The efficacy of a personalized prescription was evaluated by tumor EUD and the estimated survival time. Results: The personalized prescription for the slow-move tumors was to use 3.0–3.5 cm margins for GTV₁, and a 1.5 cm margin for GTV₂. For the average- and fast-move tumors, it was optimal to use a 6.0 cm margin for GTV₁ and then 1.5–3.0 cm margins for GTV₂, suggesting a course of whole brain therapy followed by a boost to a smaller volume. It was more effective to deliver the boost sequentially using a linearly decreasing fractional dose for all tumors. Personalized prescriptions led to surviving fractions of 0.001–0.465% compared to the standard prescription, and increased the tumor EUDs by 25.3–49.3% and estimated survival times by 7.6–22.2 months. Conclusions: Personalizing treatment margins based on the measured proliferative capacity of GBM tumor cells can potentially lead to significant improvements in tumor cell kill and related clinical outcomes.

The interventional effect of new drugs combined with the Stupp protocol on glioblastoma: A network meta-analysis

OBJECTIVE

New therapeutic agents in combination with the standard Stupp protocol (a protocol about the temozolomide combined with radiotherapy treatment with glioblastoma was research by Stupp R in 2005) were assessed to evaluate whether they were superior to the Stupp protocol alone, to determine the optimum treatment regimen for patients with newly diagnosed glioblastoma.

PATIENTS AND METHODS

We implemented a search strategy to identify studies in the following databases: PubMed, Cochrane Library, EMBASE, CNKI, CBM, Wanfang, and VIP, and assessed the quality of extracted data from the trials included. Statistical software was used to perform network meta-analysis.

RESULTS

The use of novel therapeutic agents in combination with the Stupp protocol were all shown to be superior than the Stupp protocol alone for the treatment of newly diagnosed glioblastoma, ranked as follows: cilengitide 2000mg/5/week, bevacizumab in combination with irinotecan, nimotuzumab, bevacizumab, cilengitide 2000mg/2/week, cytokine-induced killer cell immunotherapy, and the Stupp protocol. In terms of serious adverse effects, the intervention group showed a 29% increase in the incidence of adverse events compared with the control group (patients treated only with Stupp protocol) with a statistically significant difference (RR=1.29; 95%CI 1.17-1.43; P<0.001). The most common adverse events were thrombocytopenia, lymphopenia, neutropenia, pneumonia, nausea, and vomiting, none of which were significantly different between the groups except for neutropenia, pneumonia, and embolism.

CONCLUSIONS

All intervention drugs evaluated in our study were superior to the Stupp protocol alone when used in combination with it. However, we could not conclusively confirm whether cilengitide 2000mg/5/week was the optimum regime, as only one trial using this protocol was included in our study.

Update on Radiotherapy for Central Nervous System Malignancies

Malignancies arising from the central nervous system are rare. Brain metastases, in contrast, are perhaps the most common neurologic complication of cancer. Radiotherapy, as part of combined modality therapy, continues to evolve with the advancement of stereotactic radiosurgery indications, the addition of new technologies, such as alternating electric field therapy, and mounting advances in the complex biology of these entities. The explosion of new clinical trials combined with newly discovered molecular markers suggest the beginning of a paradigm shift in the management of these challenging malignancies that will allow for future risk-stratification strategies.

The oxido-metabolic driver ATF4 enhances temozolamide chemo-resistance in human gliomas

Malignant gliomas are devastating neoplasia with limited curative treatment options. Temozolomide (TMZ, Temcat^®, Temodal^® or Temodar^®) is a first-line treatment for malignant gliomas but the development of drug resistance remains a major concern. Activating transcription factor 4 (ATF4) is a critical oxido-metabolic regulator in gliomas, and its role in the pathogenesis of TMZ-resistance remains elusive. We investigated the effect of TMZ on human glioma cells under conditions of enhanced ATF4 expression (ATF4^OE) and ATF4 knock down (ATF4^KD). We monitored cell survival, ATF4 mRNA expression of ATF4 and xCT (SLC7a11) regulation within human gliomas. TMZ treatment induces a transcriptional response with elevated expression of ATF4, xCT and Nrf2, as a sign of ER stress and toxic cell damage response. ATF4 overexpression (ATF4^OE) fosters TMZ resistance in human gliomas and inhibits TMZ-induced autophagy. Conversely, ATF4 suppression by small interfering RNAs (ATF4^KD) leads to increased TMZ susceptibility and autophagy in comparison to wild type gliomas. ATF4^OE gliomas show reduced cell cycle shift and apoptotic cell death, whereas ATF4^KD gliomas reveal higher susceptibility towards cell cycle rearrangements. Hence, the migration capacity of ATF4^OE glioma cells is almost not affected by TMZ treatment. In contrast, ATF4^KD gliomas show a migratory stop following TMZ application. Mechanistically, xCT elevation is a consequence of ATF4 activation and increased levels of xCT amplifies ATF4-induced TMZ resistance. Our data show that ATF4 operates as a chemo-resistance gene in gliomas, and the tumor promoting function of ATF4 is mainly determined by its transcriptional target xCT. Therefore, therapeutic inactivation of ATF4 can be a promising strategy to overcome chemo-resistance and promote drug efficacy in human gliomas.

European Association for Neuro-Oncology (EANO) guideline on the diagnosis and treatment of adult astrocytic and oligodendroglial gliomas

The European Association for Neuro-Oncology guideline provides recommendations for the clinical care of adult patients with astrocytic and oligodendroglial gliomas, including glioblastomas. The guideline is based on the 2016 WHO classification of tumours of the central nervous system and on scientific developments since the 2014 guideline. The recommendations focus on pathological and radiological diagnostics, and the main treatment modalities of surgery, radiotherapy, and pharmacotherapy. In this guideline we have also integrated the results from contemporary clinical trials that have changed clinical practice. The guideline aims to provide guidance for diagnostic and management decisions, while limiting unnecessary treatments and costs. The recommendations are a resource for professionals involved in the management of patients with glioma, for patients and caregivers, and for health-care providers in Europe. The implementation of this guideline requires multidisciplinary structures of care, and defined processes of diagnosis and treatment.

Determining the Optimal Inhibitory Frequency for Cancerous Cells Using Tumor Treating Fields (TTFields)

Tumor Treating Fields (TTFields) are an effective treatment modality delivered via the continuous, noninvasive application of low-intensity (1-3 V/cm), alternating electric fields in the frequency range of several hundred kHz. The study of TTFields in tissue culture is carried out using the TTFields in vitro application system, which allows for the application of electric fields of varying frequencies and intensities to ceramic Petri dishes with a high dielectric constant (Ɛ > 5,000). Cancerous cell lines plated on coverslips at the bottom of the ceramic Petri dishes are subjected to TTFields delivered in two orthogonal directions at various frequencies to facilitate treatment outcome tests, such as cell counts and clonogenic assays. The results presented in this report demonstrate that the optimal frequency of the TTFields with respect to both cell counts and clonogenic assays is 200 kHz for both ovarian and glioma cells.

Angiogenesis inhibitors in tackling recurrent glioblastoma

INTRODUCTION

Despite aggressive multimodality treatment of glioblastoma, outcome remains poor and patients mostly die of local recurrences. Besides reoperation and occasionally reirradiation, systemic treatment of recurrent glioblastoma consists of alkylating chemotherapy (lomustine, temozolomide), bevacizumab and combinations thereof. Unfortunately, antiangiogenic agents failed to improve survival either as a monotherapy or in combination treatments. This review provides current insights into tumor-derived escape mechanisms and other areas of treatment failure of antiangiogenic agents in glioblastoma. Areas covered: We summarize the current literature on antiangiogenic agents in the treatment of glioblastoma, with a focus on recurrent disease. A literature search was performed using the terms 'glioblastoma', 'bevacizumab', 'antiangiogenic', 'angiogenesis', 'resistance', 'radiotherapy', 'chemotherapy' and derivations thereof. Expert commentary: New insights in glioma neoangiogenesis, increasing understanding of vascular pathway escape mechanisms, and upcoming immunotherapy approaches might revitalize the therapeutic potential of antiangiogenic agents against glioblastoma, although with a different treatment intention. The combination of antiangiogenic approaches with or without radiotherapy might still hold promise to complement the therapeutic armamentarium of fighting glioblastoma.

Novel Molecular Multilevel Targeted Antitumor Agents

A multifunctional fusion protein, IL-13.E13K-D2-NLS, effectively recognizes glioblastoma (GBM) cells and delivers its portion to the cell nucleus. IL-13.E13K-D2-NLS is composed of a cancer cell targeting ligand (IL-13.E13K), specialized cytosol translocation bacterial toxin domain 2 of Pseudomonas exotoxin A (D2) and SV40 T antigen nuclear localization signal (NLS). We have now tested whether we can produce proteins that would serve as a delivery vehicle to lysosomes and mitochondria as well. Moreover, we examined whether IL-13.E13K-D2-NLS can deliver anti-cancer drugs like doxorubicin to their nuclear site of action in cancer cells. We have thus constructed two novel proteins: IL-13.E13K-D2-LLS which incorporates lysosomal localization signal (LLS) of a human lysosomal associated membrane protein (LAMP-1) for targeting to lysosomes and IL-13-D2-KK2, which incorporates a pro-apoptotic peptide (KLAKLAK)2 (KK2) exerting its action in mitochondria. Furthermore, we have produced IL-13.E13K-D2-NLS and IL-13.E13K-D2-LLS versions containing a cysteine for site-specific conjugation with a modified doxorubicin, WP936. We found that single-chain recombinant proteins IL-13.E13K-D2-LLS and IL-13-D2-KK2 are internalized and localized mostly to the lysosomal and mitochondrial compartments, respectively, without major trafficking to cells' nuclei. We also determined that IL-13.E13K-D2-NLS-cys[WP936], IL-13.E13K-D2-LAMP-cys[WP936] and IL-13-D2-KK2 were cytotoxic to GBM cells overexpressing IL-13RA2, while much less cytotoxic to GBM cell lines expressing low levels of the receptor. IL-13.E13K-D2-NLS-cys[WP936] was the most potent of the tested anti-tumor agents including free WP936. We believe that our receptor-directed intracellular organelle-targeted proteins can be employed for numerous specific and safer treatment applications when drugs have specific intracellular sites of their action.

Prolonged Temozolomide Maintenance Therapy in Newly Diagnosed Glioblastoma

BACKGROUND

The impact of prolonging temozolomide (TMZ) maintenance beyond six cycles in newly diagnosed glioblastoma (GBM) remains a topic of discussion. We investigated the effects of prolonged TMZ maintenance on progression-free survival (PFS) and overall survival (OS).

PATIENTS AND METHODS

In this retrospective single-center cohort study, we included patients with GBM who were treated with radiation therapy with concomitant and adjuvant TMZ. For analysis, patients were considered who either completed six TMZ maintenance cycles (group B), continued with TMZ therapy beyond six cycles (group C), or stopped TMZ maintenance therapy within the first six cycles (group A). Patients with progression during the first six TMZ maintenance cycles were excluded.

RESULTS

Clinical data from 107 patients were included for Kaplan-Meier analyses and 102 for Cox regressions. Median PFS times were 8.1 months (95% confidence interval [CI] 6.1-12.4) in group A, 13.7 months (95% CI 10.6-17.5) in group B, and 20.9 months (95% CI 15.2-43.5) in group C. At first progression, response rates of TMZ/lomustine rechallenge were 47% in group B and 13% in group C. Median OS times were 12.7 months (95% CI 10.3-16.8) in group A, 25.2 months (95% CI 17.7-55.5) in group B, and 28.6 months (95% CI 24.4-open) in group C. Nevertheless, multivariate Cox regression for patients in group C compared with group B that accounted for imbalances of other risk factors showed no different relative risk (RR) for OS (RR 0.77, p = .46).

CONCLUSION

Our data do not support a general extension of TMZ maintenance therapy beyond six cycles. The Oncologist 2017;22:570-575 IMPLICATIONS FOR PRACTICE: Radiation therapy with concomitant and adjuvant temozolomide (TMZ) maintenance therapy is still the standard of care in patients below the age of 65 years in newly diagnosed glioblastoma. However, in clinical practice, many centers continue TMZ maintenance therapy beyond six cycles. The impact of this continuation is controversial and has not yet been addressed in prospective randomized clinical trials. We compared the effect of more than six cycles of TMZ in comparison with exactly six cycles on overall survival (OS) and progression-free survival (PFS) by multivariate analysis and found a benefit in PFS but not OS. Thus, our data do not suggest prolonging TMZ maintenance therapy beyond six cycles, which should be considered in neurooncological practice.

Biological activity of tumor-treating fields in preclinical glioma models

Glioblastoma is the most common and aggressive form of intrinsic brain tumor with a very poor prognosis. Thus, novel therapeutic approaches are urgently needed. Tumor-treating fields (TTFields) may represent such a novel treatment option. The aim of this study was to investigate the effects of TTFields on glioma cells, as well as the functional characterization of the underlying mechanisms. Here, we assessed the anti-glioma activity of TTFields in several preclinical models. Applying TTFields resulted in the induction of cell death in a frequency- and intensity-dependent manner in long-term glioma cell lines, as well as glioma-initiating cells. Cell death occurred in the absence of caspase activation, but involved autophagy and necroptosis. Severe alterations in cell cycle progression and aberrant mitotic features, such as poly- and micronucleation, preceded the induction of cell death. Furthermore, exposure to TTFields led to reduced migration and invasion, which are both biological hallmarks of glioma cells. The combination of TTFields with irradiation or the alkylating agent, temozolomide (TMZ), resulted in additive or synergistic effects, and the O⁶-methyl-guanine DNA methyltransferase status did not influence the efficacy of TTFields. Importantly, TMZ-resistant glioma cells were responsive to TTFields application, highlighting the clinical potential of this therapeutic approach. In summary, our results indicate that TTFields induce autophagy, as well as necroptosis and hamper the migration and invasiveness of glioma cells. These findings may allow for a more detailed clinical evaluation of TTFields beyond the clinical data available so far.

The effect of Optune™ Tumor Treating Fields transducer arrays on skin radiation dose during radiotherapy

A Phase 3 clinical study demonstrated that the addition of 200kHz Tumor Treating Fields (TTF) to temozolomide in the post-radiation (RT) phase of therapy in newly diagnosed glioblastoma increases progression free and overall survival (resulting in FDA and European Union approval). Preclinical studies have demonstrated the ability of TTF to act as a radiosensitizer, suggesting concurrent TTF and RT may have clinical utility. The removal and replacement of TTF transducer arrays from the scalps of patients on a daily basis, i.e., just before and after RT treatments, would be extremely cumbersome. Based on these considerations, phantom studies of the effect of Optune (TM) transducer arrays on radiation dose distribution were performed to evaluate the feasibility of leaving arrays in place during RT. Film measurements were performed using Gafchromic EBT3 film and an Epson 11000XL scanner. Film calibration was done based on the ratio of the red to blue color channel data. A Siemens Oncor linear accelerator operating at 6MV, 10cm×10cm field size, and 100cm source-to-film distance was used for all measurements. For each exposure, two films were stacked, providing planes of measurement that were ∼0.1 and 0.4mm in depth. Data accrued demonstrated that radiation attenuation should not be a clinically significant issue. However, TTF transducer arrays were found to cause both a radiation bolus effect, as well as an increased exit dose effect. These studies predict increased skin toxicity, which merits significant caution for further clinical development of this combination.

Tumor-treating fields plus chemotherapy versus chemotherapy alone for glioblastoma at first recurrence: a post hoc analysis of the EF-14 trial

BACKGROUND

This post hoc analysis of the EF-14 trial (NCT00916409) of tumor-treating fields (TTFields) plus temozolomide versus temozolomide alone in newly diagnosed glioblastoma compared the efficacy of TTFields plus chemotherapy (physician's choice) versus chemotherapy alone after first recurrence.

METHODS

Patients on TTFields plus temozolomide continued TTFields plus second-line chemotherapy after first recurrence. Some patients on temozolomide alone crossed over after approval of TTFields for recurrent GBM. The primary efficacy outcome was overall survival (OS).

RESULTS

After disease progression, 131 patients received TTFields plus chemotherapy and 73 chemotherapy alone. Thirteen patients in the original temozolomide-alone group crossed over to receive TTFields plus chemotherapy after disease progression, resulting in 144 patients receiving TTFields plus chemotherapy and 60 chemotherapy alone. Median follow-up was 12.6 months. Bevacizumab, alone or with cytotoxic chemotherapy, was the most frequent treatment. Median OS in the TTFields plus chemotherapy group was significantly longer versus chemotherapy alone (11.8 vs 9.2 months; HR: 0.70; 95% CI, 0.48-1.00; p=0.049). TTFields showed a low toxicity safety profile, as previously reported, with no grade 3/4 device-related adverse events.

CONCLUSION

TTFields plus chemotherapy after first disease recurrence on TTFields plus temozolomide or temozolomide alone prolonged OS in patients in the EF-14 trial.

Bevacizumab for malignant gliomas: current indications, mechanisms of action and resistance, and markers of response

Vascular endothelial growth factor (VEGF) is an attractive target of antiangiogenic therapy in glioblastomas. Bevacizumab (Bev), a humanized anti-VEGF antibody, is associated with the improvement of progression-free survival and performance status in patients with glioblastoma. However, randomized trials uniformly suggest that these favorable clinical effects of Bev do not translate into an overall survival benefit. The mechanisms of action of Bev appear to include the inhibition of tumor angiogenesis, as well as indirect effects such as the depletion of niches for glioma stem cells and stimulation of antitumor immunity. Although several molecules/pathways have been reported to mediate adaptation and resistance to Bev, including the activation of alternative pro-angiogenic pathways, the resistance mechanisms have not been fully elucidated; for example, the mechanism that reinduces tumor hypoxia remains unclarified. The identification of imaging characteristics or biomarkers predicting the response to Bev, as well as the better understanding of the mechanisms of action and resistance, is crucial to improve the overall clinical outcome and optimize individual therapy. In this article, the authors review the results of important clinical trials/studies, the current understanding of the mechanisms of action and resistance, and the knowledge of imaging characteristics and biomarkers predicting the response to Bev.

Management of GBM: a problem of local recurrence

Forty years ago, adjuvant treatment of patients with GBM using fractionated radiotherapy following surgery was shown to substantially improve survival compared to surgery alone. However, even with the addition of temozolomide to radiotherapy, overall survival is quite limited and local failure remains a fundamental problem, despite multiple attempts to increase dose to the tumor target. This review presents the historical background and clinical rationale leading to the current standard of care consisting of 60 Gy total dose in 2 Gy fractions to the MRI-defined targets in younger, high performance status patients and more hypofractionated regimens in elderly and/or debilitated patients. Particle therapies offer the potential to increase local control while reducing dose and, potentially, long-term neurocognitive toxicity. However, improvements in systemic therapies for GBM will need to be implemented before the full benefits of improved local control can be realized.

Tumor-treating fields elicit a conditional vulnerability to ionizing radiation via the downregulation of BRCA1 signaling and reduced DNA double-strand break repair capacity in non-small cell lung cancer cell lines

The use of tumor-treating fields (TTFields) has revolutionized the treatment of recurrent and newly diagnosed glioblastoma (GBM). TTFields are low-intensity, intermediate frequency, alternating electric fields that are applied to tumor regions and cells using non-invasive arrays. The predominant mechanism by which TTFields are thought to kill tumor cells is the disruption of mitosis. Using five non-small cell lung cancer (NSCLC) cell lines we found that there is a variable response in cell proliferation and cell killing between these NSCLC cell lines that was independent of p53 status. TTFields treatment increased the G2/M population, with a concomitant reduction in S-phase cells followed by the appearance of a sub-G1 population indicative of apoptosis. Temporal changes in gene expression during TTFields exposure was evaluated to identify molecular signaling changes underlying the differential TTFields response. The most differentially expressed genes were associated with the cell cycle and cell proliferation pathways. However, the expression of genes found within the BRCA1 DNA-damage response were significantly downregulated (P<0.05) during TTFields treatment. DNA double-strand break (DSB) repair foci increased when cells were exposed to TTFields as did the appearance of chromatid-type aberrations, suggesting an interphase mechanism responsible for cell death involving DNA repair. Exposing cells to TTFields immediately following ionizing radiation resulted in increased chromatid aberrations and a reduced capacity to repair DNA DSBs, which were likely responsible for at least a portion of the enhanced cell killing seen with the combination. These findings suggest that TTFields induce a state of ‘BRCAness' leading to a conditional susceptibility resulting in enhanced sensitivity to ionizing radiation and provides a strong rationale for the use of TTFields as a combined modality therapy with radiation or other DNA-damaging agents.

Acute care in glioblastoma: the burden and the consequences

Background

The utilization of inpatient medical services by patients with glioblastoma (GBM) is not well studied. We sought to describe causes, frequency, and outcomes of acute care visits in GBM.

Methods

We conducted a retrospective study of 158 GBM patients at the University of Rochester over 5 years. Electronic medical records were reviewed to identify all local and outside acute care visits. Acute care visits were defined as any encounter resulting in an emergency department visit or inpatient admission.

Results

Seventy-one percent (112/158) of GBM patients had 235 acute care visits corresponding to 163 hospitalizations (69%) and 72 emergency department visits (31%). Sixty-three percent of patients had multiple visits. Admission diagnoses were seizure (33%), neurosurgical procedure (15%), infection (12%), focal neurologic symptoms (9%), and venous thromboembolism (VTE, 9%). Forty-six patients had 1 or more visits for seizures. Median time to first acute care visit was 65.6 days and 22% of patients had an acute care visit within 30 days of diagnosis. Median length of stay was 5 days. Thirty-five percent of admitted patients were discharged home; 62% required a higher level of care than prior to admission (23% were discharged home with services, 17% to a nursing facility, 16% to hospice, 6% to acute rehab) and 3% died. Thirty-eight percent of patients had ACV within 30 days of death. Median survival was 14 months for patients who had acute care visits and 22.2 months for patients who did not.

Conclusion

The majority of GBM patients utilize acute care, most commonly for seizures. The high number of emergency department visits, short length of stay, and many patients discharged home suggest that some acute care visits may be avoidable.

Alternating electric tumor treating fields for treatment of glioblastoma: rationale, preclinical, and clinical studies

OBJECTIVE Treatment for glioblastoma (GBM) remains largely unsuccessful, even with aggressive combined treatment via surgery, radiotherapy, and chemotherapy. Tumor treating fields (TTFs) are low-intensity, intermediate-frequency, alternating electric fields that have antiproliferative properties in vitro and in vivo. The authors provide an up-to-date review of the mechanism of action as well as preclinical and clinical data on TTFs. METHODS A systematic review of the literature was performed using the terms "tumor treating fields," "alternating electric fields," "glioblastoma," "Optune," "NovoTTF-100A," and "Novocure." RESULTS Preclinical and clinical data have demonstrated the potential efficacy of TTFs for treatment of GBM, leading to several pilot studies, clinical trials, and, in 2011, FDA approval for its use as salvage therapy for recurrent GBM and, in 2015, approval for newly diagnosed GBM. CONCLUSIONS Current evidence supports the use of TTFs as an efficacious, antimitotic treatment with minimal toxicity in patients with newly diagnosed and recurrent GBM. Additional studies are needed to further optimize patient selection, determine cost-effectiveness, and assess the full impact on quality of life.

Milestones of the last 10 years: CNS cancer

For neuro-oncologists, much was accomplished in the last decade, including the establishment of the first standard of care (SOC) in this field of oncology. New treatment options boosted research in the whole field of neuro-oncology, as well clinical trials, translational and basic research. Accumulated data on molecular-genetic subgroups with distinct clinical outcomes in disease entities led to the establishment of new biomarkers and to the collaborative formulation of a new WHO classification of central nervous system tumors.

Critical review of the addition of tumor treating fields (TTFields) to the existing standard of care for newly diagnosed glioblastoma patients

Since 2005, the standard of care for patients with newly diagnosed glioblastoma (GBM) has consisted of maximal resection followed by radiotherapy plus daily temozolomide (TMZ), followed by maintenance TMZ. In patients selected for clinical trials, median overall survival (OS) and progression-free survival (PFS) with this regimen is 15-17 months and 6-7 months, respectively. There have been various, largely unsuccessful attempts to improve on this standard of care. With the FDA approval of the tumor-treating fields (TTFields) device, Optune, for recurrent GBM (2011), and the more recent EF-14 interim trial results and approval for newly diagnosed GBM patients, several questions have arisen. A roundtable of experts was convened at the 2015 ASCO meeting to engage in an open conversation and debate of the EF-14 results presented at that meeting and their implications for neuro-oncology practice and clinical research. In October 2015, subsequent to the roundtable discussion, TTFields received FDA approval for newly diagnosed GBM.

The Safety of available immunotherapy for the treatment of glioblastoma

INTRODUCTION

Glioblastoma (GBM) is the most common malignant primary brain tumor in adults. Current standard of care involves maximal surgical resection combined with adjuvant chemoradiation. Growing support exists for a role of immunotherapy in treating these tumors with the goal of targeted cytotoxicity. Here we review data on the safety for current immunotherapies being tested in GBM. Areas covered: Safety data from published clinical trials, including ongoing clinical trials were reviewed. Immunotherapeutic classes currently under investigation in GBM include various vaccination strategies, adoptive T cell immunotherapy, immune checkpoint blockade, monoclonal antibodies, and cytokine therapies. Trials include children, adolescents, and adults with either primary or recurrent GBM. Expert opinion: Based on the reviewed clinical trials, the current immunotherapies targeting GBM are safe and well-tolerated with minimal toxicities which should be noted. However, the gains in patient survival have been modest. A safe and well-tolerated combinatory immunotherapeutic approach may be essential for optimal efficacy towards GBM.

Beyond Alkylating Agents for Gliomas: Quo Vadimus?

Recent advances in therapies have yielded notable success in terms of improved survival in several cancers. However, such treatments have failed to improve outcome in patients with gliomas for whom surgery followed by radiation therapy and chemotherapy with alkylating agents remain the standard of care. Genetic and epigenetic studies have helped identify several alterations specific to gliomas. Attempts to target these altered pathways have been unsuccessful due to various factors, including tumor heterogeneity, adaptive resistance of tumor cells, and limitations of access across the blood-brain barrier. Novel therapies that circumvent such limitations have been the focus of intense study and include approaches such as immunotherapy, targeting of signaling hubs and metabolic pathways, and use of biologic agents. Immunotherapeutic approaches including tumor-targeted vaccines, immune checkpoint blockade, antibody-drug conjugates, and chimeric antigen receptor-expressing cell therapies are in various stages of clinical trials. Similarly, identification of key metabolic pathways or converging hubs of signaling pathways that are tumor specific have yielded novel targets for therapy of gliomas. In addition, the failure of conventional therapies against gliomas has led to a growing interest among patients in the use of alternative therapies, which in turn has necessitated developing evidence-based approaches to the application of such therapies in clinical studies. The development of these novel approaches bears potential for providing breakthroughs in treatment of more meaningful and improved outcomes for patients with gliomas.

Brain tumors - other treatment modalities

Management of tumors of the central nervous system is challenging for clinicians for various reasons, including complex diagnostic procedures, limited penetration of drugs into brain tissue, and the prerequisite to preserve brain function in any case of therapeutic intervention. Therapeutic success is dependent on the efforts, skills, and cooperation of involved specialists and disciplines. Knowledge and ability to apply adequate therapeutic modalities in an interdisciplinary approach in due time are crucial, necessitating coordination of diagnostic procedures and therapeutic interventions by means of multidisciplinary brain tumor boards. In this chapter we present in brief the essential current standards and future perspectives for therapy modalities that complement surgery of brain tumors.

Advances in the molecular genetics of gliomas - implications for classification and therapy

Genome-wide molecular-profiling studies have revealed the characteristic genetic alterations and epigenetic profiles associated with different types of gliomas. These molecular characteristics can be used to refine glioma classification, to improve prediction of patient outcomes, and to guide individualized treatment. Thus, the WHO Classification of Tumours of the Central Nervous System was revised in 2016 to incorporate molecular biomarkers - together with classic histological features - in an integrated diagnosis, in order to define distinct glioma entities as precisely as possible. This paradigm shift is markedly changing how glioma is diagnosed, and has important implications for future clinical trials and patient management in daily practice. Herein, we highlight the developments in our understanding of the molecular genetics of gliomas, and review the current landscape of clinically relevant molecular biomarkers for use in classification of the disease subtypes. Novel approaches to the genetic characterization of gliomas based on large-scale DNA-methylation profiling and next-generation sequencing are also discussed. In addition, we illustrate how advances in the molecular genetics of gliomas can promote the development and clinical translation of novel pathogenesis-based therapeutic approaches, thereby paving the way towards precision medicine in neuro-oncology.

Regression of Glioblastoma after Chimeric Antigen Receptor T-Cell Therapy

A patient with recurrent multifocal glioblastoma received chimeric antigen receptor (CAR)-engineered T cells targeting the tumor-associated antigen interleukin-13 receptor alpha 2 (IL13Rα2). Multiple infusions of CAR T cells were administered over 220 days through two intracranial delivery routes - infusions into the resected tumor cavity followed by infusions into the ventricular system. Intracranial infusions of IL13Rα2-targeted CAR T cells were not associated with any toxic effects of grade 3 or higher. After CAR T-cell treatment, regression of all intracranial and spinal tumors was observed, along with corresponding increases in levels of cytokines and immune cells in the cerebrospinal fluid. This clinical response continued for 7.5 months after the initiation of CAR T-cell therapy. (Funded by Gateway for Cancer Research and others; ClinicalTrials.gov number, NCT02208362 .).

First report of tumor treating fields use in combination with bevacizumab in a pediatric patient: a case report

We report the first case of a pediatric patient with glioblastoma (GBM; WHO grade IV astrocytoma) successfully treated with tumor treating fields (TTF). The patient was diagnosed with GBM when 13 years of age and progressed through surgical resection, radiotherapy and chemotherapy. Discrete tumor growth visualized on MRI with stable neurological examination was monitored for 6 months with subsequent stable disease observed radiographically and clinically for 7 months while adherent to Optune^® (TTF). TTF thereby played a role in forestalling recurrent GBM growth in this young woman for 7 months without significant adverse effects. We propose that TTF therapy is a potential valuable treatment in this small, but sick, patient population.

Radiation Therapy for Glioblastoma: American Society of Clinical Oncology Clinical Practice Guideline Endorsement of the American Society for Radiation Oncology Guideline

Purpose The American Society for Radiation Oncology (ASTRO) produced an evidence-based guideline on radiation therapy for glioblastoma. Because of its relevance to the ASCO membership, ASCO reviewed the guideline and applied a set of procedures and policies used to critically examine guidelines developed by other organizations. Methods The ASTRO guideline on radiation therapy for glioblastoma was reviewed for developmental rigor by methodologists. An ASCO endorsement panel updated the literature search and reviewed the content and recommendations. Results The ASCO endorsement panel determined that the recommendations from the ASTRO guideline, published in 2016, are clear, thorough, and based on current scientific evidence. ASCO endorsed the ASTRO guideline on radiation therapy for glioblastoma and added qualifying statements. Recommendations Partial-brain fractionated radiotherapy with concurrent and adjuvant temozolomide is the standard of care after biopsy or resection of newly diagnosed glioblastoma in patients up to 70 years of age. Hypofractionated radiotherapy for elderly patients with fair to good performance status is appropriate. The addition of concurrent and adjuvant temozolomide to hypofractionated radiotherapy seems to be safe and efficacious without impairing quality of life for elderly patients with good performance status. Reasonable options for patients with poor performance status include hypofractionated radiotherapy alone, temozolomide alone, or best supportive care. Focal reirradiation represents an option for select patients with recurrent glioblastoma, although this is not supported by prospective randomized evidence. Additional information is available at www.asco.org/glioblastoma-radiotherapy-endorsement and www.asco.org/guidelineswiki .

The effects of tumor treating fields and temozolomide in MGMT expressing and non-expressing patient-derived glioblastoma cells

A recent Phase 3 study of newly diagnosed glioblastoma (GBM) demonstrated the addition of tumor treating fields (TTFields) to temozolomide (TMZ) after combined radiation/TMZ significantly increased survival and progression free survival. Preliminary data suggested benefit with both methylated and unmethylated O-6-methylguanine-DNA methyl-transferase (MGMT) promoter status. To date, however, there have been no studies to address the potential interactions of TTFields and TMZ. Thus, the effects of TTFields and TMZ were studied in vitro using patient-derived GBM stem-like cells (GSCs) including MGMT expressing (TMZ resistant: 12.1 and 22GSC) and non-MGMT expressing (TMZ sensitive: 33 and 114GSC) lines. Dose-response curves were constructed using cell proliferation and sphere-forming assays. Results demonstrated a ⩾10-fold increase in TMZ resistance of MGMT-expressing (12.1GSCs: IC₅₀=160μM; 22GSCs: IC₅₀=44μM) compared to MGMT non-expressing (33GSCs: IC₅₀=1.5μM; 114GSCs: IC₅₀=5.2μM) lines. TTFields inhibited 12.1 GSC proliferation at all tested doses (50-500kHz) with an optimal frequency of 200kHz. At 200kHz, TTFields inhibited proliferation and tumor sphere formation of both MGMT GSC subtypes at comparable levels (12.1GSC: 74±2.9% and 38±3.2%, respectively; 22GSC: 61±11% and 38±2.6%, respectively; 33GSC: 56±9.5% and 60±7.1%, respectively; 114 GSC: 79±3.5% and 41±4.3%, respectively). In combination, TTFields (200kHz) and TMZ showed an additive anti-neoplastic effect with equal efficacy for TTFields in both cell types (i.e., ± MGMT expression) with no effect on TMZ resistance. This is the first demonstration of the effects of TTFields on cancer stem cells. The expansion of such studies may have clinical implications.

A Phase 2 Trial of Neoadjuvant Temozolomide Followed by Hypofractionated Accelerated Radiation Therapy With Concurrent and Adjuvant Temozolomide for Patients With Glioblastoma

PURPOSE

We performed a phase 2 trial of neoadjuvant temozolomide (TMZ), followed by hypofractionated accelerated radiation therapy (HART) with concurrent TMZ, and adjuvant TMZ in patients with newly diagnosed glioblastoma to determine whether neoadjuvant TMZ would safely improve outcomes in this group of patients prior to subsequent cytotoxic therapy.

METHODS AND MATERIALS

Adult patients with newly diagnosed glioblastoma and a Karnofsky Performance Status >60 were eligible. Neoadjuvant TMZ administration started 2 to 3 weeks from surgery at a daily dose of 75 mg/m² for 2 weeks prior to delivery of HART (60 Gy in 20 daily fractions) with concurrent and adjuvant TMZ. The primary endpoints were feasibility and toxicity. The secondary endpoints included overall survival (OS) and progression-free survival.

RESULTS

Fifty patients were accrued. The median follow-up period was 44.0 months for patients at risk and 22.3 months for all 50 patients. Except for 1 patient in whom infection developed and another patient with progression during HART, all patients completed protocol therapy as planned. The median OS and progression-free survival were 22.3 months (95% confidence interval, 14.6-42.7 months) and 13.7 months (95% confidence interval, 8.0-33.3 months), respectively. The 4-year OS rates were 30.4% for the entire cohort and 53.3% and 14.0% for patients with methylated (n=21) and unmethylated (n=27) MGMT gene promoter tumors, respectively. One patient had grade 5 pancytopenia during HART, and another patient had transient grade 4 hepatotoxicity. A second surgical procedure was performed in 13 patients: 2 had intracranial infection, 3 had recurrences, 4 had recurrences and radiation-induced damage, and 4 had only radiation-induced damage.

CONCLUSIONS

This novel approach of neoadjuvant TMZ is associated with an encouraging favorable long-term survival with acceptable toxicity. A future comparative trial of the efficacy of this regimen is warranted.

Emerging targeted therapies for glioma

INTRODUCTION

Gliomas are the most common malignant primary brain tumors in adults. Despite aggressive treatment with surgery, radiation and chemotherapy, these tumors are incurable and invariably recur. Molecular characterization of these tumors in recent years has advanced our understanding of gliomagenesis and offered an array of pathways that can be specifically targeted. Areas covered: The most commonly dysregulated signaling pathways found in gliomas will be discussed, as well as the biologic importance of these disrupted pathways and how each may contribute to tumor development. Our knowledge regarding these pathways are most relevant to Grade IV glioma/glioblastoma, but we will also discuss genomic categorization of low grade glioma. Further, drugs targeting single pathways, which have undergone early phase clinical trials will be reviewed, followed by an in depth discussion of emerging treatments on the horizon, which will include inhibitors of Epidermal Growth Factor Receptor (EGFR) and receptor tyrosine kinases, Phosphoinositide-3-Kinase (PI3K), angiogenesis, cell cycle and mutant Isocitrate Dehydrogenase (IDH) mutations. Expert opinion: Results from single agent targeted therapy trials have been modest. Lack of efficacy may stem from a combination of poor blood brain barrier penetration, the genetically heterogeneous make-up of the tumors and the emergence of resistance mechanisms. These factors can be overcome by rational drug design that capitalizes on ways to target critical pathways and limits upregulation of redundant pathways.

An Overview of Sub-Cellular Mechanisms Involved in the Action of TTFields

Long-standing research on electric and electromagnetic field interactions with biological cells and their subcellular structures has mainly focused on the low- and high-frequency regimes. Biological effects at intermediate frequencies between 100 and 300 kHz have been recently discovered and applied to cancer cells as a therapeutic modality called Tumor Treating Fields (TTFields). TTFields are clinically applied to disrupt cell division, primarily for the treatment of glioblastoma multiforme (GBM). In this review, we provide an assessment of possible physical interactions between 100 kHz range alternating electric fields and biological cells in general and their nano-scale subcellular structures in particular. This is intended to mechanistically elucidate the observed strong disruptive effects in cancer cells. Computational models of isolated cells subject to TTFields predict that for intermediate frequencies the intracellular electric field strength significantly increases and that peak dielectrophoretic forces develop in dividing cells. These findings are in agreement with in vitro observations of TTFields' disruptive effects on cellular function. We conclude that the most likely candidates to provide a quantitative explanation of these effects are ionic condensation waves around microtubules as well as dielectrophoretic effects on the dipole moments of microtubules. A less likely possibility is the involvement of actin filaments or ion channels.

Therapeutic Potential of Curcumin for the Treatment of Brain Tumors

Brain malignancies currently carry a poor prognosis despite the current multimodal standard of care that includes surgical resection and adjuvant chemotherapy and radiation. As new therapies are desperately needed, naturally occurring chemical compounds have been studied for their potential chemotherapeutic benefits and low toxicity profile. Curcumin, found in the rhizome of turmeric, has extensive therapeutic promise via its antioxidant, anti-inflammatory, and antiproliferative properties. Preclinical in vitro and in vivo data have shown it to be an effective treatment for brain tumors including glioblastoma multiforme. These effects are potentiated by curcumin's ability to induce G2/M cell cycle arrest, activation of apoptotic pathways, induction of autophagy, disruption of molecular signaling, inhibition of invasion, and metastasis and by increasing the efficacy of existing chemotherapeutics. Further, clinical data suggest that it has low toxicity in humans even at large doses. Curcumin is a promising nutraceutical compound that should be evaluated in clinical trials for the treatment of human brain tumors.

Enhancing Predicted Efficacy of Tumor Treating Fields Therapy of Glioblastoma Using Targeted Surgical Craniectomy: A Computer Modeling Study

Objective

The present work proposes a new clinical approach to TTFields therapy of glioblastoma. The approach combines targeted surgical skull removal (craniectomy) with TTFields therapy to enhance the induced electrical field in the underlying tumor tissue. Using computer simulations, we explore the potential of the intervention to improve the clinical efficacy of TTFields therapy of brain cancer.

Methods

We used finite element analysis to calculate the electrical field distribution in realistic head models based on MRI data from two patients: One with left cortical/subcortical glioblastoma and one with deeply seated right thalamic anaplastic astrocytoma. Field strength was assessed in the tumor regions before and after virtual removal of bone areas of varying shape and size (10 to 100 mm) immediately above the tumor. Field strength was evaluated before and after tumor resection to assess realistic clinical scenarios.

Results

For the superficial tumor, removal of a standard craniotomy bone flap increased the electrical field strength by 60–70% in the tumor. The percentage of tissue in expected growth arrest or regression was increased from negligible values to 30–50%. The observed effects were highly focal and targeted at the regions of pathology underlying the craniectomy. No significant changes were observed in surrounding healthy tissues. Median field strengths in tumor tissue increased with increasing craniectomy diameter up to 50–70 mm. Multiple smaller burr holes were more efficient than single craniectomies of equivalent area. Craniectomy caused no significant field enhancement in the deeply seated tumor, but rather a focal enhancement in the brain tissue underlying the skull defect.

Conclusions

Our results provide theoretical evidence that small and clinically feasible craniectomies may provide significant enhancement of TTFields intensity in cerebral hemispheric tumors without severely compromising brain protection or causing unacceptable heating in healthy tissues. A clinical trial is being planned to validate safety and efficacy.

Rationale and Background on Tumor-Treating Fields for Glioblastoma

BACKGROUND

More than 150 years after the first description of glioma cells, patients with glioblastoma (GBM) continue to have a poor prognosis despite standard-of-care therapy. With the introduction of tumor-treating fields (TTFields) therapy for the treatment of recurrent GBM in 2011 and for newly diagnosed GBM in 2015, the opportunity to increase progression-free survival and overall survival while improving quality of life provides a welcome option.

OBJECTIVES

This article describes how TTFields therapy may be used in the treatment of patients with recurrent GBM.

METHODS

This article provides oncology nurses with two case studies that examine how TTFields therapy can be integrated into the overall treatment paradigm.

FINDINGS

These two patient case studies demonstrate the autonomy and lack of adverse effects that TTFields therapy offers to patients with GBM.

Glioblastoma: Overview of Disease and Treatment

BACKGROUND

Glioblastoma (GBM) is the most common and aggressive malignant brain tumor in adults. Current treatment options at diagnosis are multimodal and include surgical resection, radiation, and chemotherapy. Significant advances in the understanding of the molecular pathology of GBM and associated cell signaling pathways have opened opportunities for new therapies for recurrent and newly diagnosed disease. Innovative treatments, such as tumor-treating fields (TTFields) and immunotherapy, give hope for enhanced survival.

OBJECTIVES

This article reviews the background, risks, common complications, and treatment options for GBM.

METHODS

A brief review of GBM, treatment options, and a look at new therapies that have been approved for new and recurrent disease are included in this article.

FINDINGS

Despite aggressive resection and combined modality adjuvant treatment, most GBMs recur. Treatments, such as TTFields, drugs to target molecular receptors, and immunotherapy, are promising new options.