Bevacizumab does not increase the risk of remote relapse in malignant glioma

Changes in the Relapse Pattern and Prognosis of Glioblastoma After Approval of First-Line Bevacizumab: A Single-Center Retrospective Study

BACKGROUND

Controversies exist regarding the aggressive recurrence of glioblastoma after bevacizumab treatment. We analyzed the clinical impact of bevacizumab approval in Japan by evaluating the clinical course and relapse pattern in patients with glioblastoma.

METHODS

We included 100 patients with IDH-wildtype glioblastoma from September 2006 to February 2018 in our institution. The patients were classified into pre-bevacizumab (n = 51) and post-bevacizumab (n = 49) groups. Overall, progression-free, deterioration-free, and post-progression survivals were compared. We analyzed the relapse pattern of 72 patients, whose radiographic progressions were evaluated.

RESULTS

Significant improvement in progression-free (pre-bevacizumab, 7.5 months; post-bevacizumab, 9.9 months; P = 0.0153) and deterioration-free (pre-bevacizumab, 8.5 months; post-bevacizumab, 13.8 months; P = 0.0046) survivals were seen. These survival prolongations were strongly correlated (r: 0.91, P < 0.0001). The non-enhancing tumor pattern was novel in the post-bevacizumab era (5/33). The presence of a non-enhancing tumor did not indicate poor post-progression survival (hazard ratio: 0.82 [0.26-2.62], P = 0.7377). The rate of early focal recurrence was significantly lower (P = 0.0155) in the post-bevacizumab (4/33) than in the pre-bevacizumab (18/39) era. There was a significant decrease in early focal recurrence after approval of bevacizumab in patients with unresectable tumors (P = 0.0110). The treatment era was significantly correlated with a decreased rate of early focal recurrence (P = 0.0021, univariate analysis; P = 0.0144, multivariate analysis).

CONCLUSIONS

Approval of first-line bevacizumab in Japan for unresectable tumors may prevent early progression and clinical deterioration of glioblastoma without worsening the clinical course following relapse.

Radiological Recurrence Patterns after Bevacizumab Treatment of Recurrent High-Grade Glioma: A Systematic Review and Meta-Analysis

Objective

To categorize the radiological patterns of recurrence after bevacizumab treatment and to derive the pooled proportions of patients with recurrent malignant glioma showing the different radiological patterns.

Materials and Methods

A systematic literature search in the Ovid-MEDLINE and EMBASE databases was performed to identify studies reporting radiological recurrence patterns in patients with recurrent malignant glioma after bevacizumab treatment failure until April 10, 2019. The pooled proportions according to radiological recurrence patterns (geographically local versus non-local recurrence) and predominant tumor portions (enhancing tumor versus non-enhancing tumor) after bevacizumab treatment were calculated. Subgroup and meta-regression analyses were also performed.

Results

The systematic review and meta-analysis included 17 articles. The pooled proportions were 38.3% (95% confidence interval [CI], 30.6–46.1%) for a geographical radiologic pattern of non-local recurrence and 34.2% (95% CI, 27.3–41.5%) for a non-enhancing tumor-predominant recurrence pattern. In the subgroup analysis, the pooled proportion of non-local recurrence in the patients treated with bevacizumab only was slightly higher than that in patients treated with the combination with cytotoxic chemotherapy (34.9% [95% CI, 22.8–49.4%] versus 22.5% [95% CI, 9.5–44.6%]).

Conclusion

A substantial proportion of high-grade glioma patients show non-local or non-enhancing radiologic patterns of recurrence after bevacizumab treatment, which may provide insight into surrogate endpoints for treatment failure in clinical trials of recurrent high-grade glioma.

CIRP regulates BEV-induced cell migration in gliomas

Purpose

A better understanding of the underlying molecular mechanisms in treatment failure of bevacizumab (BEV) for malignant glioma would contribute to overcome therapeutic resistance.

Methods

Here, we used a quantitative proteomic method to identify molecular signatures of glioblastoma cell after BEV treatment by two-dimensional liquid chromatography-tandem mass spectrometry analysis and 6-plex iTRAQ quantification. Next, the function of cold-inducible RNA-binding protein (CIRP), one of the most significantly affected proteins by drug treatment, was evaluated in drug resistance of glioma cells by invasion assays and animal xenograft assays. Target molecules bound by CIRP were determined using RNA-binding protein immunoprecipitation and microarray analysis. Then, these mRNAs were identified by quantitative real-time PCR.

Results

Eighty-seven proteins were identified with significant fold changes. The biological functional analysis indicated that most of the proteins were involved in the process of cellular signal transduction, cell adhesion, and protein transport. The expression of CIRP greatly decreased after BEV treatment, and ectopic expression of CIRP abolished cell migration in BEV-treated glioma cells. In addition, CIRP could bind mRNA of CXCL12 and inhibit BEV-induced increase of CXCL12 in glioma cells.

Conclusion

These data suggested that CIRP may take part in BEV-induced migration of gliomas by binding of migration-relative RNAs.

Differential Effects of Ang-2/VEGF-A Inhibiting Antibodies in Combination with Radio- or Chemotherapy in Glioma

Antiangiogenic strategies have not shown striking antitumor activities in the majority of glioma patients so far. It is unclear which antiangiogenic combination regimen with standard therapy is most effective. Therefore, we compared anti-VEGF-A, anti-Ang2, and bispecific anti-Ang-2/VEGF-A antibody treatments, alone and in combination with radio- or temozolomide (TMZ) chemotherapy, in a malignant glioma model using multiparameter two-photon in vivo microscopy in mice. We demonstrate that anti-Ang-2/VEGF-A lead to the strongest vascular changes, including vascular normalization, both as monotherapy and when combined with chemotherapy. The latter was accompanied by the most effective chemotherapy-induced death of cancer cells and diminished tumor growth. This was most probably due to a better tumor distribution of the drug, decreased tumor cell motility, and decreased formation of resistance-associated tumor microtubes. Remarkably, all these parameters where reverted when radiotherapy was chosen as combination partner for anti-Ang-2/VEGF-A. In contrast, the best combination partner for radiotherapy was anti-VEGF-A. In conclusion, while TMZ chemotherapy benefits most from combination with anti-Ang-2/VEGF-A, radiotherapy does from anti-VEGF-A. The findings imply that uninformed combination regimens of antiangiogenic and cytotoxic therapies should be avoided.

Radiologic progression of glioblastoma under therapy-an exploratory analysis of AVAglio

Background

In this exploratory analysis of AVAglio, a randomized phase III clinical study that investigated the addition of bevacizumab (Bev) to radiotherapy/temozolomide in newly diagnosed glioblastoma, we aim to radiologically characterize glioblastoma on therapy until progression and investigate whether the type of radiologic progression differs between treatment arms and is related to survival and molecular data.

Methods

Five progression types (PTs) were categorized using an adapted algorithm according to MRI contrast enhancement behavior in T1- and T2-weighted images in 621 patients (Bev, n = 299; placebo, n = 322). Frequencies of PTs (designated as classic T1, cT1 relapse, T2 diffuse, T2 circumscribed, and primary nonresponder), time to progression (PFS), and overall survival (OS) were assessed within each treatment arm and compared with molecular subtypes and O6-methylguanine DNA methyltransferase (MGMT) promoter methylation status.

Results

PT frequencies differed between the Bev and placebo arms, except for "T2 diffuse" (12.4% and 7.1%, respectively). PTs showed differences in PFS and OS; with "T2 diffuse" being associated with longest survival. Complete disappearance of contrast enhancement during treatment ("cT1 relapse") showed longer survival than only partial contrast enhancement decrease ("classic T1"). "T2 diffuse" was more commonly MGMT hypermethylated. Only weak correlations to molecular subtypes from primary tissue were detected.

Conclusions

Progression of glioblastoma under therapy can be characterized radiologically. These radiologic phenotypes are influenced by treatment and develop differently over time with differential outcomes. Complete resolution of contrast enhancement during treatment is a favorable factor for outcome.

Neuroimaging classification of progression patterns in glioblastoma: a systematic review

BACKGROUND

Our primary objective was to report the current neuroimaging classification systems of spatial patterns of progression in glioblastoma. In addition, we aimed to report the terminology used to describe 'progression' and to assess the compliance with the Response Assessment in Neuro-Oncology (RANO) Criteria.

METHODS

We conducted a systematic review to identify all neuroimaging studies of glioblastoma that have employed a categorical classification system of spatial progression patterns. Our review was registered with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) registry.

RESULTS

From the included 157 results, we identified 129 studies that used labels of spatial progression patterns that were not based on radiation volumes (Group 1) and 50 studies that used labels that were based on radiation volumes (Group 2). In Group 1, we found 113 individual labels and the most frequent were: local/localised (58%), distant/distal (51%), diffuse (20%), multifocal (15%) and subependymal/subventricular zone (15%). We identified 13 different labels used to refer to 'progression', of which the most frequent were 'recurrence' (99%) and 'progression' (92%). We identified that 37% (n = 33/90) of the studies published following the release of the RANO classification were adherent compliant with the RANO criteria.

CONCLUSIONS

Our review reports significant heterogeneity in the published systems used to classify glioblastoma spatial progression patterns. Standardization of terminology and classification systems used in studying progression would increase the efficiency of our research in our attempts to more successfully treat glioblastoma.

Tumor growth patterns of MGMT-non-methylated glioblastoma in the randomized GLARIUS trial

BACKGROUND

We evaluated patterns of tumor growth in patients with newly diagnosed MGMT-non-methylated glioblastoma who were assigned to undergo radiotherapy in conjunction with bevacizumab/irinotecan (BEV/IRI) or standard temozolomide (TMZ) within the randomized phase II GLARIUS trial.

METHODS

In 142 patients (94 BEV/IRI, 48 TMZ), we reviewed magnetic resonance imaging scans at baseline and first tumor recurrence. Based on contrast-enhanced T1-weighted and fluid-attenuated inversion recovery images, we assessed tumor growth patterns and tumor invasiveness. Tumor growth patterns were classified as either multifocal or local at baseline and recurrence; at first recurrence, we additionally assessed whether distant lesions appeared. Invasiveness was determined as either diffuse or non-diffuse. Associations with treatment arms were calculated using Fisher's exact test.

RESULTS

At baseline, 115 of 142 evaluable patients (81%) had a locally confined tumor. Between treatment arms, there was no significant difference in the fraction of tumors that changed from an initially local tumor growth pattern to a multifocal pattern (12 and 13%, p = 0.55). Distant lesions appeared in 17% (BEV/IRI) and 13% (TMZ) of patients (p = 0.69). 15% of patients in the BEV/IRI arm and 8% in the TMZ arm developed a diffuse growth pattern from an initially non-diffuse pattern (p = 0.42).

CONCLUSIONS

The tumor growth and invasiveness patterns do not differ between BEV/IRI and TMZ-treated MGMT-non-methylated glioblastoma patients in the GLARIUS trial. BEV/IRI was not associated with an increased rate of multifocal, distant, or highly invasive tumors at the time of recurrence.

Bevacizumab for Patients with Recurrent Multifocal Glioblastomas

In patients with glioblastoma, antiangiogenic therapy with bevacizumab (BEV) has been shown to improve progression-free survival (PFS), but not overall survival (OS). Especially in patients with an unusual infiltrative phenotype as seen in multifocal glioblastoma, the use of BEV therapy is still more controversial. Therefore, we prepared a retrospective case series with 16 patients suffering from a multifocal glioblastoma treated with BEV. We compared these patients to a matched control cohort of 16 patients suffering from glioblastoma with a single lesion treated with BEV. The objective of this study was to evaluate whether the course of disease differs in glioblastoma patients with a multifocal disease pattern compared to those with a single lesion only. Patients were treated with BEV monotherapy or BEV in combination with irinotecan or lomustine (CCNU). Response rates and PFS were similar in both groups. There was a trend for an unfavorable OS in the patient group with multifocal glioblastoma, which was expected due to the generally worse prognosis of multifocal glioblastoma. We investigated whether BEV therapy affects the invasive growth pattern as measured by the appearance of new lesions on magnetic resonance imaging (MRI). Under BEV therapy, there was a trend for a lower frequency of new lesions both in multifocal and solitary glioblastoma. Based on these results, BEV therapy at relapse appears to be justified to no lesser extent in multifocal glioblastoma than in solitary glioblastoma.

Bevacizumab for Patients with Recurrent Gliomas Presenting with a Gliomatosis Cerebri Growth Pattern

Bevacizumab has been shown to improve progression-free survival and neurologic function, but failed to improve overall survival in newly diagnosed glioblastoma and at first recurrence. Nonetheless, bevacizumab is widely used in patients with recurrent glioma. However, its use in patients with gliomas showing a gliomatosis cerebri growth pattern is contentious. Due to the marked diffuse and infiltrative growth with less angiogenic tumor growth, it may appear questionable whether bevacizumab can have a therapeutic effect in those patients. However, the development of nodular, necrotic, and/or contrast-enhancing lesions in patients with a gliomatosis cerebri growth pattern is not uncommon and may indicate focal neo-angiogenesis. Therefore, control of growth of these lesions as well as control of edema and reduction of steroid use may be regarded as rationales for the use of bevacizumab in these patients. In this retrospective patient series, we report on 17 patients with primary brain tumors displaying a gliomatosis cerebri growth pattern (including seven glioblastomas, two anaplastic astrocytomas, one anaplastic oligodendroglioma, and seven diffuse astrocytomas). Patients have been treated with bevacizumab alone or in combination with lomustine or irinotecan. Seventeen matched patients treated with bevacizumab for gliomas with a classical growth pattern served as a control cohort. Response rate, progression-free survival, and overall survival were similar in both groups. Based on these results, anti-angiogenic therapy with bevacizumab should also be considered in patients suffering from gliomas with a mainly infiltrative phenotype.

Prolonged survival after bevacizumab rechallenge in glioblastoma patients with previous response to bevacizumab†

Background

The use of bevacizumab for recurrent glioblastoma is controversial. Here we show data on patients who responded to bevacizumab, then stopped bevacizumab for any reason other than progression and were rechallenged with bevacizumab at the time of subsequent progression.

Methods

This retrospective study included 28 patients, classified in 2 cohorts: those for whom the first exposure to bevacizumab (BEV-1) was first-line treatment for newly diagnosed glioblastoma (Bev-F; N = 12) and those for whom BEV-1 was second- or third-line treatment for recurrent disease after standard treatment (Bev-S; N = 16).

Results

All patients received standard radiotherapy plus temozolomide. Bev-F patients also received concomitant bevacizumab. All 28 patients received a total of 57 treatment lines with bevacizumab (12 first-line and 45 second- or further-line). Twenty-nine lines were rechallenges (BEV-2 [N = 26] or BEV-3 [N = 3]). Objective response to rechallenge was 58.6% and clinical benefit was 89.6%. Overall survival (OS) was 55 months for RPA class IV and 26.7 months for RPA class V patients (P = .01). OS was 26.7 months for Bev-F patients and 52.1 months for Bev-S patients (P = .004). Post-progression survival was 20 months for Bev-F patients and 39.6 months for Bev-S patients (HR = 0.26; P = .007).

Conclusion

This is the largest study to examine the impact of a bevacizumab rechallenge in glioblastoma patients who had responded to previous bevacizumab treatment but who stopped before progression. Our findings indicate that these patients can attain a second response or clinical benefit from re-introduction of bevacizumab. The potential benefit from intermittent versus continuous treatment warrants comparison in clinical trials.

Change in 18F-Fluoromisonidazole PET Is an Early Predictor of the Prognosis in the Patients with Recurrent High-Grade Glioma Receiving Bevacizumab Treatment

Background

Bevacizumab (BEV), a humanized monoclonal antibody, become a currently important chemotherapeutic option for the patients with recurrent glioma. The aim of this retrospective study is to investigate whether ¹⁸F-Fluoromisonidazole (FMISO) PET have the potential to detect BEV-resistant gliomas in the early-stage.

Methods

We reviewed the FMISO PET and MRI appearances before and 3 to 4 courses after BEV treatment on 18 recurrent glioma patients. FMISO accumulation was assessed by visual inspection and semi-quantitative values which were tumor-to-normal (T/N) ratio and hypoxic volume. MRI responses were evaluated based on RANO (Response Assessment in Neuro-Oncology) criteria. The prognostic analysis was performed in relation to the response assessment by FMISO PET and MRI using overall survival (OS) after BEV application.

Results

After BEV application, MRI revealed partial response in 14 of 18 patients (78%), of which 9 patients also demonstrated decreased FMISO accumulation. These 9 patients (50%) were classified as “MRI-FMISO double responder”. As for the other 5 patients (28%), FMISO accumulation volumes increased or remained stable after BEV treatment although partial responses were achieved on MRI. Therefore, these cases were classified as “MRI-only responder”. The remaining 4 patients (22%) did not show treatment response on FMISO PET or MRI (“non-responder”). MRI-FMISO double responders showed significantly longer OS than that in other groups (median 12.4 vs 5.7 months; P < 0.001), whereas there were no overall survival difference between MRI-only responders and non-responders (median OS, 5.7 and 4.8 months; P = 0.58). Among the pre-treatment clinical factors, high FMISO T/N ratio was a significant prognostic factor of overall survival in these patients under the assessment of Cox proportional hazard model.

Conclusions

Recurrent gliomas with decreasing FMISO accumulation after short-term BEV application could derive a survival benefit from BEV treatment. Change in FMISO PET appearance can identify BEV-resistant gliomas in early-stage regardless of MRI findings in a comprehensible way.

Evaluation of pseudoprogression rates and tumor progression patterns in a phase III trial of bevacizumab plus radiotherapy/temozolomide for newly diagnosed glioblastoma

BACKGROUND

Evaluation of glioblastoma disease status may be complicated by treatment-induced changes and discordance between enhancing and nonenhancing MRI. Exploratory analyses are presented (prospectively assessed pseudoprogression and therapy-related tumor pattern changes) from the AVAglio trial (bevacizumab or placebo plus radiotherapy/temozolomide for newly diagnosed glioblastoma).

METHODS

MRI was done every 8 weeks (beginning 4 wk after chemoradiotherapy) using prespecified and standardized T1 and T2 protocols. Progressive disease (PD) at 10 weeks was reconfirmed at 18 weeks to distinguish pseudoprogression. Progression-free survival (PFS), excluding cases of confirmed pseudoprogression, was assessed (post-hoc/exploratory). Tumor progression patterns were determined at each disease assessment/PD (prespecified/exploratory).

RESULTS

Of patients with PD in the bevacizumab and placebo arms, 143/354 (40.4%) and 155/387 (40.1%), respectively, had PD due to contrast-enhancing lesions, and 51/354 (14.4%) and 53/387 (13.7%) had PD due to nonenhancing lesions. Of all patients in the bevacizumab arm (n = 458), 2.2% had confirmed pseudoprogression versus 9.3% in the placebo arm (n = 463). Baseline characteristics did not differ between patients with/without pseudoprogression (including for MGMT status). Excluding confirmed pseudoprogression, PFS (hazard ratio: 0.65, 95% CI: 0.56-0.75; P < .0001, bevacizumab vs placebo) was comparable to the intent-to-treat population. At PD, most patients had the same tumor focus (local/multifocal, >84%) and infiltrative profile (>88%) as at baseline; no shift to a diffuse or multifocal phenotype was observed.

CONCLUSIONS

Pseudoprogression complicated progression assessment in a small but relevant number of patients but had negligible impact on PFS. Bevacizumab did not appear to adversely impact tumor progression patterns.

Glioma cell VEGFR-2 confers resistance to chemotherapeutic and antiangiogenic treatments in PTEN-deficient glioblastoma

Loss of the tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a prerequisite for tumor cell-specific expression of vascular endothelial growth factor receptor (VEGFR)-2 in glioblastoma defining a subgroup prone to develop evasive resistance towards antiangiogenic treatments. Immunohistochemical analysis of human tumor tissues showed VEGFR-2 expression in glioma cells in 19% of specimens examined, mainly in the infiltration zone. Glioma cell VEGFR-2 positivity was restricted to PTEN-deficient tumor specimens. PTEN overexpression reduced VEGFR-2 expression in vitro, as well as knock-down of raptor or rictor. Genetic interference with VEGFR-2 revealed proproliferative, antiinvasive and chemoprotective functions for VEGFR-2 in glioma cells. VEGFR-2-dependent cellular effects were concomitant with activation of 'kappa-light-chain-enhancer' of activated B-cells, protein kinase B, and N-myc downstream regulated gene 1. Two-photon in vivo microscopy revealed that expression of VEGFR-2 in glioma cells hampers antiangiogenesis. Bevacizumab induces a proinvasive response in VEGFR-2-positive glioma cells. Patients with PTEN-negative glioblastomas had a shorter survival after initiation of bevacizumab therapy compared with PTEN-positive glioblastomas. Conclusively, expression of VEGFR-2 in glioma cells indicates an aggressive glioblastoma subgroup developing early resistance to temozolomide or bevacizumab. Loss of PTEN may serve as a biomarker identifying those tumors upfront by routine neuropathological methods.

Limited role for transforming growth factor-β pathway activation-mediated escape from VEGF inhibition in murine glioma models

BACKGROUND

The vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-β pathways regulate key biological features of glioblastoma. Here we explore whether the TGF-β pathway, which promotes angiogenesis, invasiveness, and immunosuppression, acts as an escape pathway from VEGF inhibition.

METHODS

The role of the TGF-β pathway in escape from VEGF inhibition was assessed in vitro and in vivo and by gene expression profiling in syngeneic mouse glioma models.

RESULTS

We found that TGF-β is an upstream regulator of VEGF, whereas VEGF pathway activity does not alter the TGF-β pathway in vitro. In vivo, single-agent activity was observed for the VEGF antibody B20-4.1.1 in 3 and for the TGF-β receptor 1 antagonist LY2157299 in 2 of 4 models. Reduction of tumor volume and blood vessel density, but not induction of hypoxia, correlated with benefit from B20-4.1.1. Reduction of phosphorylated (p)SMAD2 by LY2157299 was seen in all models but did not predict survival. Resistance to B20 was associated with anti-angiogenesis escape pathway gene expression, whereas resistance to LY2157299 was associated with different immune response gene signatures in SMA-497 and GL-261 on transcriptomic profiling. The combination of B20 with LY2157299 was ineffective in SMA-497 but provided prolongation of survival in GL-261, associated with early suppression of pSMAD2 in tumor and host immune cells, prolonged suppression of angiogenesis, and delayed accumulation of tumor infiltrating microglia/macrophages.

CONCLUSIONS

Our study highlights the biological heterogeneity of murine glioma models and illustrates that cotargeting of the VEGF and TGF-β pathways might lead to improved tumor control only in subsets of glioblastoma.

Perioperative cerebral ischemia promote infiltrative recurrence in glioblastoma

Background

Hypoxia is a key driver for infiltrative growth in experimental gliomas. It has remained elusive whether tumor hypoxia in glioblastoma patients contributes to distant or diffuse recurrences. We therefore investigated the influence of perioperative cerebral ischemia on patterns of progression in glioblastoma patients.

Methods

We retrospectively screened MRI scans of 245 patients with newly diagnosed glioblastoma undergoing resection for perioperative ischemia near the resection cavity. 46 showed relevant ischemia nearby the resection cavity. A control cohort without perioperative ischemia was generated by a 1:1 matching using an algorithm based on gender, age and adjuvant treatment. Both cohorts were analyzed for patterns of progression by a blinded neuroradiologist.

Results

The percentage of diffuse or distant recurrences at first relapse was significantly higher in the cohort with perioperative ischemia (61.1%) compared to the control cohort (19.4%). The results of the control cohort matched well with historical data. The change in patterns of progression was not associated with a difference in survival.

Conclusions

This study reveals an unrecognized association of perioperative cerebral ischemia with distant or diffuse recurrence in glioblastoma. It is the first clinical study supporting the concept that hypoxia is a key driver of infiltrative tumor growth in glioblastoma patients.

Current concepts in brain tumor imaging

Magnetic resonance imaging (MRI) is the most useful imaging tool in the evaluation of patients with brain tumors. Most information is supplied by standard anatomic images that were developed in the 1980s and 1990s. More recently, functional imaging including diffusion and perfusion MRI has been investigated as a way to generate predictive and prognostic biomarkers for high-grade glioma evaluation, but additional research is needed to establish the added benefits of these indices to standard MRI. Response critieria for high-grade gliomas have recently been updated by the Response Assessment in Neuro-Oncology (RANO) working group. The new criteria account for nonenhancing tumor in addition to the contrast-enhancing abnormalities on which older criteria relied. This issue has recently come to the fore with the introduction of the antiangiogenic agent bevacizumab into standard treatment for recurrent glioblastoma. Because of its potent antipermeability effect, contrast enhancement is markedly reduced in patients who receive bevacizumab. The RANO criteria also address the phenomenon of pseudoprogression, in which there may be transient MRI worsening of a glioblastoma following concurrent radiotherapy and temozolomide.

Bevacizumab and other novel therapies for recurrent oligodendroglial tumors

Oligodendroglioma (WHO Grade 2) and anaplastic oligodendroglioma (WHO Grade 3) are glial tumors composed of neoplastic cellular elements that resemble oligodendrocytes. The treatment of recurrent, alkylator refractory oligodendroglial tumors is challenging given the paucity of effective treatment and lack of randomized controlled trials on which to base therapy. Notwithstanding the lack of prospective, randomized data, treatment of oligodendroglial tumors with bevacizumab can be recommended tentatively recognizing that preliminary studies suggest efficacy. Somatic mutations of the isocitrate dehydrogenase enzymes (IDH1 and IDH2) appear to play a critical role in the pathogenesis of most oligodendroglial tumors and agents that target these mutations are a potential therapeutic option. Additionally, reversal of CpG island hypermethylated phenotype status through inhibition of DNA methyltransferase with an inhibitor such as decitabine may provide a target for future studies.

Current status and future directions of anti-angiogenic therapy for gliomas

Molecular targets for the pathological vasculature are the vascular endothelial growth factor (VEGF)/VEGF receptor axis, integrins, angiopoietins, and platelet-derived growth factor receptor (PDGFR), as well as several intracellular or downstream effectors like protein kinase C beta and mammalian target of rapamycin (mTOR). Besides hypoxic damage or tumor cell starvation, preclinical models imply vessel independent tumor regression and suggest differential effects of anti-angiogenic treatments on tumorous and nontumorous precursor cells or the immune system. Despite compelling preclinical data and positive data in other cancers, the outcomes of clinical trials with anti-angiogenic agents in gliomas by and large have been disappointing and include VEGF blockage with bevacizumab, integrin inhibition with cilengitide, VEGF receptor inhibition with sunitinib or cediranib, PDGFR inhibition with imatinib or dasatinib, protein kinase C inhibition with enzastaurin, and mTOR inhibition with sirolimus, everolimus, or temsirolimus. Importantly, there is a lack of real understanding for this negative data. Anti-angiogenic therapies have stimulated the development of standardized imaging assessment and the integration of functional MRI sequences into daily practice. Here, we delineate directions in the identification of molecularly or image-based defined subgroups, anti-angiogenic cotreatment for immunotherapy, and the potential of ongoing trials or modified targets to change the game.

Pros and cons of current brain tumor imaging

Over the past 20 years, very few agents have been approved for the treatment of brain tumors. Recent studies have highlighted some of the challenges in assessing activity in novel agents for the treatment of brain tumors. This paper reviews some of the key challenges related to assessment of tumor response to therapy in adult high-grade gliomas and discusses the strengths and limitations of imaging-based endpoints. Although overall survival is considered the "gold standard" endpoint in the field of oncology, progression-free survival and response rate are endpoints that hold great value in neuro-oncology. Particular focus is given to advancements made since the January 2006 Brain Tumor Endpoints Workshop, including the development of Response Assessment in Neuro-Oncology criteria, the value of T2/fluid-attenuated inversion recovery, use of objective response rates and progression-free survival in clinical trials, and the evaluation of pseudoprogression, pseudoresponse, and inflammatory response in radiographic images.

[Treatment of the glioma microenvironment]

Therapeutic concepts for malignant gliomas increasingly target the genetically non-transformed tumor stroma rather than the tumor cells themselves. There are two particular compartments of the tumor stroma which are currently tackled: the vascular compartment by using antiangiogenic treatment with the aim of vascular normalization and the immune compartment with the aim of enhancing or inducing anti-tumor immunity. Although the vascular endothelial growth factor (VEGF) A antibody bevacizumab has not been approved for the treatment of malignant glioma in European countries, there is evidence from smaller trials of biological efficacy particularly in recurrent disease and the results of a large European phase III study testing the clinical efficacy are currently expected. Immunotherapies are on the verge of entering the clinical arena with the first randomized phase III clinical trials having already been completed. In these studies, active vaccination and checkpoint inhibitors which are approved for other tumor entities are being tested. This article provides an overview on the current antiangiogenic and immunological therapies for gliomas, summarizes the results of clinical trials and discusses further developments.

Chemotherapy in glioma

The treatment of glial brain tumors begins with surgery, and standard adjuvant treatment at the end of the past millennium for high-grade glioma and high-risk low-grade glioma was radiotherapy and chemotherapy was given at recurrence. However, over the past 10 years much has changed regarding the role of chemotherapy in gliomas and it is now clear that chemotherapy has a role in the treatment of almost all newly diagnosed diffuse gliomas (WHO grade II-IV). This is the result of several prospective studies that showed survival benefit after combined chemoradiotherapy with temozolomide in glioblastoma (WHO grade IV) or after procarbazine, CCNU (lomustine) and vincristine chemotherapy in diffuse low-grade (WHO grade II) and anaplastic (WHO grade III) glioma. The current standard of treatment for diffuse gliomas is described in this overview and in addition some attention is given to targeted therapies.

Mechanisms of evasive resistance to anti-VEGF therapy in glioblastoma

Angiogenesis inhibitors targeting the VEGF signaling pathway have been US FDA approved for various cancers including glioblastoma (GBM), one of the most lethal and angiogenic tumors. This has led to the routine use of the anti-VEGF antibody bevacizumab in recurrent GBM, conveying substantial improvements in radiographic response, progression-free survival and quality of life. Despite these encouraging beneficial effects, patients inevitably develop resistance and frequently fail to demonstrate significantly better overall survival. Unlike chemotherapies, to which tumors exhibit resistance due to genetic mutation of drug targets, emerging evidence suggests that tumors bypass antiangiogenic therapy while VEGF signaling remains inhibited through a variety of mechanisms that are just beginning to be recognized. Because of the indirect nature of resistance to VEGF inhibitors there is promise that strategies combining angiogenesis inhibitors with drugs targeting such evasive resistance pathways will lead to more durable antiangiogenic efficacy and improved patient outcomes. Further identifying and understanding of evasive resistance mechanisms and their clinical importance in GBM relapse is therefore a timely and critical issue.

Antiangiogenic therapy for glioblastoma: current status and future prospects

Glioblastoma is characterized by high expression levels of proangiogenic cytokines and microvascular proliferation, highlighting the potential value of treatments targeting angiogenesis. Antiangiogenic treatment likely achieves a beneficial impact through multiple mechanisms of action. Ultimately, however, alternative proangiogenic signal transduction pathways are activated, leading to the development of resistance, even in tumors that initially respond. The identification of biomarkers or imaging parameters to predict response and to herald resistance is of high priority. Despite promising phase II clinical trial results and patient benefit in terms of clinical improvement and longer progression-free survival, an overall survival benefit has not been demonstrated in four randomized phase III trials of bevacizumab or cilengitide in newly diagnosed glioblastoma or cediranib or enzastaurin in recurrent glioblastoma. However, future studies are warranted. Predictive markers may allow appropriate patient enrichment, combination with chemotherapy may ultimately prove successful in improving overall survival, and novel agents targeting multiple proangiogenic pathways may prove effective.

Update on anti-angiogenic treatment for malignant gliomas

Malignant gliomas are the most common primary brain tumor found in adults. Unfortunately, the prognosis for these type of tumors remains dismal despite aggressive treatment with surgical resection, radiation and chemotherapy. Therefore, therapeutics aimed at disrupting the angiogenesis of these tumors is being utilized in to improve survival outcomes and quality of life. This paper reviews the history of antiangiogenic agents in malignant gliomas, discusses the FDA approval of bevacizumab as monotherapy in recurrent glioblastoma and the subsequent controversy, and analyzes the most recent newly diagnosed trials of RTOG 0825 and AVAglio. Additionally, the results of the latest trials with antiangiogenic agents and possible biomarkers are reviewed. Multiple questions remain regarding the potential benefit of antiangiogenic treatments in patients with glioblastoma. Future clinical trials should be designed to learn more about these drugs, to optimize their future use.

The impact of bevacizumab treatment on survival and quality of life in newly diagnosed glioblastoma patients

Glioblastoma multiforme (GBM) remains one of the most devastating tumors, and patients have a median survival of 15 months despite aggressive local and systemic therapy, including maximal surgical resection, radiation therapy, and concomitant and adjuvant temozolomide. The purpose of antineoplastic treatment is therefore to prolong life, with a maintenance or improvement of quality of life. GBM is a highly vascular tumor and overexpresses the vascular endothelial growth factor A, which promotes angiogenesis. Preclinical data have suggested that anti-angiogenic treatment efficiently inhibits tumor growth. Bevacizumab is a humanized monoclonal antibody against vascular endothelial growth factor A, and treatment has shown impressive response rates in recurrent GBM. In addition, it has been shown that response is correlated to prolonged survival and improved quality of life. Several investigations in newly diagnosed GBM patients have been performed during recent years to test the hypothesis that newly diagnosed GBM patients should be treated with standard multimodality treatment, in combination with bevacizumab, in order to prolong life and maintain or improve quality of life. The results of these studies along with relevant preclinical data will be described, and pitfalls in clinical and paraclinical endpoints will be discussed.

Standards of care and novel approaches in the management of glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor in adults. Standard therapeutic approaches provide modest improvement in the progression-free and overall survival, necessitating the investigation of novel therapies. We review the standard treatment options for GBM and evaluate the results obtained in clinical trials for promising novel approaches, including the inhibition of angiogenesis, targeted approaches against molecular pathways, immunotherapies, and local treatment with low voltage electric fields.

Survival outcome of early versus delayed bevacizumab treatment in patients with recurrent glioblastoma

Bevacizumab (BEV) is widely used for treatment of patients with recurrent glioblastoma. It is not known if there are differences in outcome between early versus delayed BEV treatment of recurrent glioblastoma. We examined the relationship between the time of starting BEV treatment and outcomes in patients with recurrent glioblastoma. In this retrospective chart review, we identified patients with recurrent glioblastoma diagnosed between 2005 and 2011 who were treated with BEV alone or BEV-containing regimens. Data was analyzed to determine overall survival (OS) from time of diagnosis and progression free survival (PFS) from time of starting BEV. A total of 298 patients were identified, 112 patients received early BEV, 133 patients received delayed BEV, and 53 patients were excluded because they either progressed within 3 months of radiation or received BEV at the time of diagnosis. There was no significant difference in PFS between patients that received early BEV and those that received delayed BEV (5.2 vs. 4.3 months, p = 0.2). Patients treated with delayed BEV had longer OS when compared to those treated with early BEV (25.9 vs. 20.8 months, p = 0.005). In patients with recurrent glioblastoma, there was no significant difference in PFS from the time of starting BEV between early and delayed BEV. Although patients treated with delayed BEV seemed to have longer OS, a conclusion regarding OS outcome requires further prospective trials. These results may indicate that delaying treatment with BEV is not detrimental for survival of patients with recurrent glioblastoma.

Single-agent bevacizumab or lomustine versus a combination of bevacizumab plus lomustine in patients with recurrent glioblastoma (BELOB trial): a randomised controlled phase 2 trial

BACKGROUND

Treatment options for recurrent glioblastoma are scarce, with second-line chemotherapy showing only modest activity against the tumour. Despite the absence of well controlled trials, bevacizumab is widely used in the treatment of recurrent glioblastoma. Nonetheless, whether the high response rates reported after treatment with this drug translate into an overall survival benefit remains unclear. We report the results of the first randomised controlled phase 2 trial of bevacizumab in recurrent glioblastoma.

METHODS

The BELOB trial was an open-label, three-group, multicentre phase 2 study undertaken in 14 hospitals in the Netherlands. Adult patients (≥18 years of age) with a first recurrence of a glioblastoma after temozolomide chemoradiotherapy were randomly allocated by a web-based program to treatment with oral lomustine 110 mg/m(2) once every 6 weeks, intravenous bevacizumab 10 mg/kg once every 2 weeks, or combination treatment with lomustine 110 mg/m(2) every 6 weeks and bevacizumab 10 mg/kg every 2 weeks. Randomisation of patients was stratified with a minimisation procedure, in which the stratification factors were centre, Eastern Cooperative Oncology Group performance status, and age. The primary outcome was overall survival at 9 months, analysed by intention to treat. A safety analysis was planned after the first ten patients completed two cycles of 6 weeks in the combination treatment group. This trial is registered with the Nederlands Trial Register (www.trialregister.nl, number NTR1929).

FINDINGS

Between Dec 11, 2009, and Nov 10, 2011, 153 patients were enrolled. The preplanned safety analysis was done after eight patients had been treated, because of haematological adverse events (three patients had grade 3 thrombocytopenia and two had grade 4 thrombocytopenia) which reduced bevacizumab dose intensity; the lomustine dose in the combination treatment group was thereafter reduced to 90 mg/m(2). Thus, in addition to the eight patients who were randomly assigned to receive bevacizumab plus lomustine 110 mg/m(2), 51 patients were assigned to receive bevacizumab alone, 47 to receive lomustine alone, and 47 to receive bevacizumab plus lomustine 90 mg/m(2). Of these patients, 50 in the bevacizumab alone group, 46 in the lomustine alone group, and 44 in the bevacizumab and lomustine 90 mg/m(2) group were eligible for analyses. 9-month overall survival was 43% (95% CI 29-57) in the lomustine group, 38% (25-51) in the bevacizumab group, 59% (43-72) in the bevacizumab and lomustine 90 mg/m(2) group, 87% (39-98) in the bevacizumab and lomustine 110 mg/m(2) group, and 63% (49-75) for the combined bevacizumab and lomustine groups. After the reduction in lomustine dose in the combination group, the combined treatment was well tolerated. The most frequent grade 3 or worse toxicities were hypertension (13 [26%] of 50 patients in the bevacizumab group, three [7%] of 46 in the lomustine group, and 11 [25%] of 44 in the bevacizumab and lomustine 90 mg/m(2) group), fatigue (two [4%], four [9%], and eight [18%]), and infections (three [6%], two [4%], and five [11%]). At the time of this analysis, 144/148 (97%) of patients had died and three (2%) were still on treatment.

INTERPRETATION

The combination of bevacizumab and lomustine met prespecified criteria for assessment of this treatment in further phase 3 studies. However, the results in the bevacizumab alone group do not justify further studies of this treatment.

FUNDING

Roche Nederland and KWF Kankerbestrijding.

Metabolic impact of anti-angiogenic agents on U87 glioma cells

BACKGROUND

Glioma cells not only secrete high levels of vascular endothelial growth factor (VEGF) but also express VEGF receptors (VEGFR), supporting the existence of an autocrine loop. The direct impact on glioma cells metabolism of drugs targeting the VEGF pathway, such as Bevacizumab (Bev) or VEGFR Tyrosine Kinase Inhibitor (TKI), is poorly known.

MATERIAL AND METHODS

U87 cells were treated with Bev or SU1498, a selective VEGFR2 TKI. VEGFR expression was checked with FACS flow cytometry and Quantitative Real-Time PCR. VEGF secretion into the medium was assessed with an ELISA kit. Metabolomic studies on cells were performed using High Resolution Magic Angle Spinning Spectroscopy (HR-MAS).

RESULTS

U87 cells secreted VEGF and expressed low level of VEGFR2, but no detectable VEGFR1. Exposure to SU1498, but not Bev, significantly impacted cell proliferation and apoptosis. Metabolomic studies with HR MAS showed that Bev had no significant effect on cell metabolism, while SU1498 induced a marked increase in lipids and a decrease in glycerophosphocholine. Accordingly, accumulation of lipid droplets was seen in the cytoplasm of SU1498-treated U87 cells.

CONCLUSION

Although both drugs target the VEGF pathway, only SU1498 showed a clear impact on cell proliferation, cell morphology and metabolism. Bevacizumab is thus less likely to modify glioma cells phenotype due to a direct therapeutic pressure on the VEGF autocrine loop. In patients treated with VEGFR TKI, monitoring lipids with magnetic resonance spectroscopic (MRS) might be a valuable marker to assess drug cytotoxicity.

Glutamate as chemotactic fuel for diffuse glioma cells: are they glutamate suckers?

Diffuse gliomas comprise a group of primary brain tumors that originate from glial (precursor) cells and present as a variety of malignancy grades which have in common that they grow by diffuse infiltration. This phenotype complicates treatment enormously as it precludes curative surgery and radiotherapy. Furthermore, diffusely infiltrating glioma cells often hide behind a functional blood-brain barrier, hampering delivery of systemically administered therapeutic and diagnostic compounds to the tumor cells. The present review addresses the biological mechanisms that underlie the diffuse infiltrative phenotype, knowledge of which may improve treatment strategies for this disastrous tumor type. The invasive phenotype is specific for glioma: most other brain tumor types, both primary and metastatic, grow as delineated lesions. Differences between the genetic make-up of glioma and that of other tumor types may therefore help to unravel molecular pathways, involved in diffuse infiltrative growth. One such difference concerns mutations in the NADP(+)-dependent isocitrate dehydrogenase (IDH1 and IDH2) genes, which occur in >80% of cases of low grade glioma and secondary glioblastoma. In this review we present a novel hypothesis which links IDH1 and IDH2 mutations to glutamate metabolism, possibly explaining the specific biological behavior of diffuse glioma.

Controlling tumor invasion: bevacizumab and BMP4 for glioblastoma

AIM

Bevacizumab has been reported to result in increased tumor invasion when used to treat malignant glioma. We hypothesized that BMP4 would prevent diffuse tumor infiltration induced by bevacizumab for malignant glioma in a xenograft model.

METHODS

Human glioblastoma (GBM) tumor cells were implanted in the striatum of immunocompromised mice. The animals were treated with bevacizumab and BMP4. Tumor growth and invasion were measured.

RESULTS

The bevacizumab-treated mice had increased survival compared with control animals (p = 0.02). BMP4 alone did not result in improved survival (p = 1.0). The bevacizumab (p = 0.006) and bevacizumab plus BMP4 (p = 0.006) groups demonstrated significantly decreased total tumor size compared with control. Tumor invasion was significantly decreased in the bevacizumab (p = 0.005), BMP4 (p = 0.04) alone and bevacizumab plus BMP4 (p = 0.002) groups compared with control. No synergistic effect between bevacizumab and BMP4 was observed.

CONCLUSION

Bevacizumab treatment did not result in diffuse infiltration of human GBM in a mouse xenograft model. BMP4 did have an independent favorable effect on GBM that was not synergistic with bevacizumab treatment.

Bevacizumab and fotemustine for recurrent glioblastoma: a phase II study of AINO (Italian Association of Neuro-Oncology)

The optimal combination of bevacizumab with cytotoxic or cytostatic drugs in recurrent glioblastoma is unknown. We performed a phase 2 trial of combined bevacizumab and fotemustine for patients with glioblastoma at first relapse after radiotherapy and temozolomide. The primary endpoint was 6-month progression-free survival (PFS), while secondary endpoints were overall survival (OS), response rate based on RANO criteria and toxicity. Fifty-four patients with recurrent GBM were enrolled. The authors observed a 6-month PFS rate of 42.6% (95% CI 29.3-55.2) and a median PFS of 5.2 months (95% CI 3.8-6.6). The median OS was 9.1 months (95% CI 7.3-10.3). Twenty-eight patients (52%) had a radiographic response, and a significant neurological improvement with steroid reduction was observed in 25/42 symptomatic patients (60%). MGMT promoter methylation was significantly associated with improved PFS in univariate analysis. Most unifocal tumors at baseline had a focal enhancing progression (76%), while the diffuse non-enhancing progression accounted for 9.5%. Response or survival were not associated with any pattern of progression. Survival after failure of treatment was short. Twelve out of 54 patients (22%) discontinued fotemustine for grade 3/4 myelotoxicity, while 4/54 (7.4%) discontinued bevacizumab. This study failed to demonstrate a superiority of the combination of bevacizumab and fotemustine over either bevacizumab or fotemustine alone as historical controls. Future studies should explore alternative regimens of combination of the two drugs.

Towards optimizing the sequence of bevacizumab and nitrosoureas in recurrent malignant glioma

Studies on the monoclonal VEGF-A antibody bevacizumab gave raise to questions regarding the lack of an overall survival benefit, the optimal timing in the disease course and potential combination and salvage therapies. We retrospectively assessed survival, radiological progression type on bevacizumab and efficacy of salvage therapies in 42 patients with recurrent malignant gliomas who received bevacizumab and nitrosourea sequentially. 15 patients received bevacizumab followed by nitrosourea at progression and 27 patients vice versa. Time to treatment failure, defined as time from initiation of one to failure of the other treatment, was similar in both groups (9.6 vs. 9.2 months, log rank p = 0.19). Progression-free survival on nitrosoureas was comparable in both groups, while progression-free survival on bevacizumab was longer in the group receiving bevacizumab first (5.3 vs. 4.1 months, log rank p = 0.03). Survival times were similar for patients with grade III (n = 9) and grade IV (n = 33) tumors. Progression-free survival on bevacizumab for patients developing contrast-enhancing T1 progression was longer than for patients who displayed a non-enhancing T2 progression. However, post-progression survival times after bevacizumab failure were not different. Earlier treatment with bevacizumab was not associated with better outcome in this series. The fact that earlier as compared to later bevacizumab treatment does not result in a different time to treatment failure highlights the challenge for first-line or recurrence trials with bevacizumab to demonstrate an overall survival benefit if crossover of bevacizumab-naïve patients after progression occurs.

Delayed leptomeningeal and subependymal seeding after multiple surgeries for supratentorial diffuse low-grade gliomas in adults

OBJECT

Diffuse WHO Grade II glioma (diffuse low-grade glioma [DLGG]) is an infiltrative brain tumor that usually migrates along the white matter fibers. The delayed CSF dissemination of supratentorial DLGGs is an exceptional complication and is rarely described in adults. Here, the authors report outcomes in a surgical series of 9 patients with DLGGs with subsequent leptomeningeal and/or subependymal seeding (LMSS) following multiple incomplete resections.

METHODS

The authors performed a retrospective review of patients who underwent surgery for histopathologically confirmed WHO Grade II gliomas between 1998 and 2012 and experienced a secondary CSF spread. Information regarding clinical features, surgical procedures, histopathological results, adjuvant treatment, and clinical outcomes was collected and analyzed.

RESULTS

Nine consecutive patients were included in this study. There were 6 men and 3 women whose mean age was 35.5 years (range 22-59 years) at the time of initial symptom onset. All patients underwent surgery with the aid of intraoperative mapping, with incomplete tumor removal because of invasion of eloquent structures. The neuropathological examination diagnosed a DLGG in all cases (7 oligodendrogliomas, 1 astrocytoma, and 1 oligoastrocytoma). Five patients had a 1p19q codeletion. Because of tumor regrowth, the 9 patients underwent reoperation (2 surgeries in 6 cases and 3 surgeries in 3 cases), again with incomplete resection. There were no surgical complications. Adjuvant therapy (radiotherapy and chemotherapy) was administered in all patients because of progression to a higher grade of malignancy that was histopathologically confirmed in all tumors. The patients suddenly worsened, and the diagnosis of LMSS was made with a mean delay of 77 months (range 27-140 months) after the initial symptom onset. Six patients benefited from salvage chemotherapy while palliative care was chosen in 3 cases. The median survival in the 6 patients who underwent LMSS treatment was significantly longer than that in the 3 patients who did not receive salvage chemotherapy (p = 0.03). Indeed, all patients died, with a mean delay between the diagnosis of LMSS and death of 11 months (range 2-38 months) and with a mean delay between the initial symptom onset and death of 88 months (range 34-144 months).

CONCLUSIONS

Cerebrospinal fluid dissemination of DLGG is a rare but possible event. It can occur throughout the progression of WHO Grade II oligodendrogliomas, oligoastrocytomas, and astrocytomas, regardless of 1p19q status. This complication seems to appear in patients who have undergone multiple incomplete resections. Salvage therapy can be considered in patients with good neurological status. However, LMSS is associated with a decreased overall survival. Therefore, this rare entity deserves further multicenter studies to better understand its pathophysiology and to adapt therapeutic strategies.

Efficacy of salvage stereotactic radiotherapy for recurrent glioma: impact of tumor morphology and method of target delineation on local control

In this study, we assessed the efficacy of salvage stereotactic radiotherapy (SRT) for recurrent glioma. From August 2008 to December 2012, 30 patients with recurrent glioma underwent salvage SRT. The initial histological diagnoses were World Health Organization (WHO) grades II, III, and IV in 6, 9, and 15 patients, respectively. Morphologically, the type of recurrence was classified as diffuse or other. Two methods of clinical target delineation were used: A, a contrast-enhancing tumor; or B, a contrast-enhancing tumor with a 3–10-mm margin and/or surrounding fluid attenuation inversion recovery (FLAIR) high-intensity areas. The prescribed dose was 22.5–35 Gy delivered in five fractions at an isocenter using a dynamic conformal arc technique. The overall survival (OS) and local control probability (LCP) after SRT were calculated using the Kaplan–Meier method. A univariate analysis was used to test the effect of clinical variables on OS/LCP. The median follow-up period was 272 days after SRT. The OS and LCP were 83% and 56% at 6 months after SRT, respectively. Morphologically, the tumor type correlated significantly with both OS and LCP (P = 0.006 and <0.001, respectively). The method of target delineation also had a significant influence on LCP (P = 0.016). Grade 3 radiation necrosis was observed in two patients according to Common Terminology Criteria for Adverse Events, version 3. Salvage SRT was safe and effective for recurrent glioma, especially non-diffuse recurrences. Improved local control might be obtained by adding a margin to contrast-enhancing tumors or including increased FLAIR high-intensity areas.

FLAIR-only progression in bevacizumab-treated relapsing glioblastoma does not predict short survival

OBJECTIVES

In this study, we analyzed the prognostic value of different MRI progression patterns for survival in patients with recurrent malignant glioma treated with the vascular endothelial growth factor antibody bevacizumab.

PATIENTS AND METHODS

Twenty-six adult patients with recurrent malignant glioma treated with bevacizumab or bevacizumab/irinotecan were retrospectively analyzed for the development of contrast-enhanced (T1-weighted MRI) and T2/FLAIR lesions. According to the progression pattern, patients were divided into 3 subgroups: (1) patients with primarily progressive contrast-enhanced lesions in the first MRI after initiation of therapy ('primary PD group'); (2) patients with stable or regressive enhanced lesions but progressive FLAIR lesions ('FLAIR-only PD group'), and (3) patients with stable or regressive contrast-enhanced T1 and FLAIR lesions ('no PD group').

RESULTS

Overall survival (OS) in the 6 patients in the FLAIR-only PD group was not significantly different from the 11 patients in the no PD group (median 311 vs. 254 days, respectively). In contrast, survival in the FLAIR-only PD group was significantly better (p = 0.025) than in the primary PD group.

CONCLUSION

FLAIR-only progression is not an independent prognostic factor negatively influencing OS in recurrent glioblastoma treated with bevacizumab and should not lead to discontinuation of bevacizumab therapy.

Refined brain tumor diagnostics and stratified therapies: the requirement for a multidisciplinary approach

Individualized therapies are popular current concepts in oncology and first steps towards stratified medicine have now been taken in neurooncology through implementation of stratified therapeutic approaches. Knowledge about the molecular basis of brain tumors has expanded greatly in recent years and a few molecular alterations are studied routinely because of their clinical relevance. However, no single targeted agent has yet been fully approved for the treatment of glial brain tumors. In this review, we argue that multidisciplinary and integrated approaches are essential for translational research and the development of new treatments for patients with malignant gliomas, and we present a conceptual framework in which to place the components of such an interdisciplinary approach. We believe that this ambitious goal can be best realized through strong cooperation of brain tumor centers with local hospitals and physicians; such an approach enables close dialogue between expert subspecialty clinicians and local therapists to consider all aspects of this increasingly complex set of diseases.

Bevacizumab-based therapy in relapsed glioblastoma: rationale and clinical experience to date

Relapsed glioblastoma (GBM) has an extremely poor prognosis and remains an invariably fatal disease, with a median overall survival of 6-7 months. Despite numerous clinical trials over the past 20-30 years, treatment options for relapsed GBM remain limited. In recent years, significant research efforts have focused on the use of antiangiogenic therapies for the treatment of GBM. Bevacizumab is a humanized monoclonal antibody that specifically inhibits the proangiogenic VEGF, with well-established clinical efficacy in a number of solid malignancies, which is now under investigation for the treatment of GBM. In this review, we discuss the available data regarding bevacizumab-based therapy in relapsed GBM, highlighting its potential and ongoing challenges in this difficult-to-treat disease.

Disseminated progression of glioblastoma after treatment with bevacizumab

OBJECTIVES

Reports of glioblastoma (GBM) progression following treatment with bevacizumab indicate that a subset of patients develop disseminated, often minimally enhancing tumors that differ from the typical pattern of focal recurrence. We have reviewed our institutional experience with bevacizumab for GBM to evaluate the prognostic factors and outcomes of patients with disseminated progression.

PATIENTS AND METHODS

Medical records of patients treated for GBM at the University of California San Francisco from 2005 to 2009 were reviewed. Patients receiving bevacizumab for focal disease were evaluated and imaging was reviewed to identify patients who progressed in a disseminated pattern. Tumor and treatment factors were compared between focal and disseminated progressors to identify predictive factors for dissemination. Clinical outcomes were compared between progression groups.

RESULTS

Seventy-one patients received adjuvant bevacizumab at some point in their disease course in addition to surgical resection and standard chemoradiotherapy. Of these, 12 patients (17%) had disseminated progression after bevacizumab. There were no differences in patient demographics, surgical treatment, or bevacizumab administration between disseminated and focal progressors. Length of bevacizumab treatment for disseminated progressors trended toward increased time (7.4 vs. 5.4 months) but was not statistically significant (p=0.1). Although progression-free survival and overall survival did not differ significantly between progression groups (median survival from progression was 3.8 vs. 4.6 months, p=0.5), over 30% of focal progressors had a subsequent resection and enrollment in a surgically based clinical trial, whereas none of the disseminated progressors had further surgical intervention. Compared to previously published reports of GBM dissemination with and without prior bevacizumab treatment, our patients had a rate of disease dissemination similar to the baseline rate observed in patients treated without bevacizumab.

CONCLUSION

The risk of dissemination does not appear to be considerably increased due to the use of bevacizumab, and the pattern of disease at progression does not affect subsequent survival. Therefore, the risk of dissemination should not influence the decision to treat with bevacizumab, especially for recurrent disease.

Angiogenic inhibition in high-grade gliomas: past, present and future

High-grade gliomas, especially glioblastoma (GBM), are among the most aggressive and vascularized tumors. Angiogenesis plays a significant role in tumor growth and survival, and thus offers a target for anticancer treatment. Bevacizumab, a humanized monoclonal antibody against VEGF, was approved by the US FDA as a single agent for the treatment of recurrent glioblastoma. Significant radiographic response and progression-free survival were seen with bevacizumab treatment. However, benefits to overall survival remain undetermined. Other antiangiogenic strategies targeting VEGF, VEGF receptor (VEGFR) and other angiogenic factors have also been examined. Tumor progression after antiangiogenic treatment is inevitable, and effective salvage therapy is yet to be identified. Mechanisms of resistance to antiangiogenic therapy include activation of alternative proangiogenic pathways and increased tumor invasion. Strategies targeting these escape mechanisms are currently being investigated. The use of antiangiogenic drugs is generally well tolerated, although rare and potentially life-threatening adverse effects have been identified. With the striking antipermeability effect of anti-VEGF inhibitors, assessment of true tumor response has become a challenge. The Response Assessment in Neuro-Oncology Working Group has developed new criteria for clinical trials in patients with high-grade glioma. Identification of neuroimaging advances and biologic markers will greatly enhance treatment strategies for these patients.

Phospholipid metabolites in recurrent glioblastoma: in vivo markers detect different tumor phenotypes before and under antiangiogenic therapy

Purpose

Metabolic changes upon antiangiogenic therapy of recurrent glioblastomas (rGBMs) may provide new biomarkers for treatment efficacy. Since in vitro models showed that phospholipid membrane metabolism provides specific information on tumor growth we employed in-vivo MR-spectroscopic imaging (MRSI) of human rGBMs before and under bevacizumab (BVZ) to measure concentrations of phosphocholine (PCho), phosphoethanolamine (PEth), glycerophosphocholine (GPC), and glyceroethanolamine (GPE).

Methods

¹H and ³¹P MRSI was prospectively performed in 32 patients with rGBMs before and under BVZ therapy at 8 weeks intervals until tumor progression. Patients were dichotomized into subjects with long overall survival (OS) (>median OS) and short OS (<median OS) survival time from BVZ-onset. Metabolite concentrations from tumor tissue and their ratios were compared to contralateral normal-appearing tissue (control).

Results

Before BVZ, ¹H-detectable choline signals (total GPC and PCho) in rGBMs were elevated but significance failed after dichotomizing. For metabolite ratios obtained by ³¹P MRSI, the short-OS group showed higher PCho/GPC (p = 0.004) in rGBMs compared to control tissue before BVZ while PEth/GPE was elevated in rGBMs of both groups (long-OS p = 0.04; short-OS p = 0.003). Under BVZ, PCho/GPC and PEth/GPE in the tumor initially decreased (p = 0.04) but only PCho/GPC re-increased upon tumor progression (p = 0.02). Intriguingly, in normal-appearing tissue an initial PEth/GPE decrease (p = 0.047) was followed by an increase at the time of tumor progression (p = 0.031).

Conclusion

An elevated PCho/GPC ratio in the short-OS group suggests that it is a negative predictive marker for BVZ efficacy. These gliomas may represent a malignant phenotype even growing under anti-VEGF treatment. Elevated PEth/GPE may represent an in-vivo biomarker more sensitive to GBM infiltration than MRI.

Targeting Src family kinases inhibits bevacizumab-induced glioma cell invasion

Anti-VEGF antibody therapy with bevacizumab provides significant clinical benefit in patients with recurrent glioblastoma multiforme (GBM). Unfortunately, progression on bevacizumab therapy is often associated with a diffuse disease recurrence pattern, which limits subsequent therapeutic options. Therefore, there is an urgent need to understand bevacizumab's influence on glioma biology and block it's actions towards cell invasion.

To explore the mechanism(s) of GBM cell invasion we have examined a panel of serially transplanted human GBM lines grown either in short-term culture, as xenografts in mouse flank, or injected orthotopically in mouse brain. Using an orthotopic xenograft model that exhibits increased invasiveness upon bevacizumab treatment, we also tested the effect of dasatinib, a broad spectrum SFK inhibitor, on bevacizumab-induced invasion.

We show that 1) activation of Src family kinases (SFKs) is common in GBM, 2) the relative invasiveness of 17 serially transplanted GBM xenografts correlates strongly with p120 catenin phosphorylation at Y228, a Src kinase site, and 3) SFK activation assessed immunohistochemically in orthotopic xenografts, as well as the phosphorylation of downstream substrates occurs specifically at the invasive tumor edge. Further, we show that SFK signaling is markedly elevated at the invasive tumor front upon bevacizumab administration, and that dasatinib treatment effectively blocked the increased invasion induced by bevacizumab.

Our data are consistent with the hypothesis that the increased invasiveness associated with anti-VEGF therapy is due to increased SFK signaling, and support testing the combination of dasatinib with bevacizumab in the clinic.

Diagnostic and therapeutic avenues for glioblastoma: no longer a dead end?

Glioblastomas are heterogeneous neoplasms that are driven by complex signalling pathways, and are among the most aggressive and challenging cancers to treat. Despite standard treatment with resection, radiation and chemotherapy, the prognosis of patients with glioblastomas remains poor. An increasing understanding of the molecular pathogenesis of glioblastomas has stimulated the development of novel therapies, including the use of molecular-targeted agents. Identification and validation of diagnostic, prognostic and predictive biomarkers has led to the advancement of clinical trial design, and identification of glioblastoma subgroups with a more-favourable prognosis and response to therapy. In this Review, we discuss common molecular alterations relevant to the biology of glioblastomas, targeted, antiangiogenic and immunotherapies that have impacted on the treatment of this disease, and the challenges and pitfalls associated with these therapies. In addition, we emphasize current biomarkers relevant to the management of patients with glioblastoma.