Patterns of failure following treatment for glioblastoma multiforme and anaplastic astrocytoma

Changing paradigms for targeted therapies against diffuse infiltrative gliomas: tackling a moving target

Introduction: Gliomas are highly heterogeneous primary brain tumors which result in a disproportionately high degree of morbidity and mortality despite their locoregional occurrence. Advances in the understanding of the biological makeup of these malignancies have yielded a number of potential tumor-driving pathways which have been identified as rational targets for therapy. However, early trials of agents that target these pathways have uniformly failed to yield improvement in outcomes in patients with malignant gliomas. Areas covered: This review provides an overview of the most common biological features of gliomas and the strategies to target the same; in addition, the current status of immunotherapy and biological therapies are outlined and the future directions to tackle the challenges of therapy for gliomas are examined. Expert opinion: The limitations of current treatments are attributed to the inability of most of these agents to cross the blood-brain barrier and to the intrinsic heterogeneity of the tumors that result in treatment resistance. The recent emergence of immune-mediated and biological therapies and of agents that target metabolic pathways in gliomas have provided strategies that may overcome tumor heterogeneity and ongoing trials of such agents are anticipated to yield improved outcomes.

Identification of PEPT2 as an important candidate molecule in 5-ALA-mediated fluorescence-guided surgery in WHO grade II/III gliomas

PURPOSE

5-aminolevulinic acid (5-ALA) fluorescence-guided surgery (FGS) appears to be a promising treatment for glioma. However, 5-ALA-mediated fluorescence cannot always be detected in grade II/III gliomas. We hypothesized that gene expression patterns in the Protoporphyrin IX (PpIX) synthesis pathway may be associated with intraoperative fluorescence status of grade II/III gliomas, and then attempted to identify the key molecule of 5-ALA-mediated fluorescence.

METHODS

Using 50 surgically obtained specimens, which were diagnosed as grade II and III gliomas, we analyzed gene expression within the PpIX synthesis pathway to identify candidate molecules according to intraoperative 5-ALA-mediated fluorescence status. The most likely candidate gene was selected and confirmed by protein expression analysis. To evaluate the biological function of the molecule in PpIX synthesis, functional analysis was performed using specific, small interference (si)RNA in the SW-1783 human grade III glioma cell line.

RESULTS

Among the genes involved in the porphyrin synthesis pathway, the mRNA expression of Peptide transporter 2 (PEPT2) in FGS fluorescence-positive gliomas was significantly higher than that in fluorescence-negative gliomas. Protein expression of PEPT2 was also significantly higher in the fluorescence-positive gliomas, which was confirmed by western blot analysis and immunofluorescence analysis. The siRNA-mediated downregulation of the mRNA and protein expression of PEPT2 led to decreased PpIX fluorescence intensity, as confirmed by fluorescence spectrum analysis.

CONCLUSIONS

The results suggest PEPT2 is an important candidate molecule in 5-ALA-mediated FGS in grade II/III gliomas. As the overexpression of PEPT2 was associated with higher PpIX fluorescence intensity, PEPT2 may improve fluorescence-guided resection in grade II/III gliomas.

Residual Tumor Volume, Cell Volume Fraction, and Tumor Cell Kill During Fractionated Chemoradiation Therapy of Human Glioblastoma using Quantitative Sodium MR Imaging

PURPOSE

Spatial and temporal patterns of response of human glioblastoma to fractionated chemoradiation are described by changes in the bioscales of residual tumor volume (RTV), tumor cell volume fraction (CVF), and tumor cell kill (TCK), as derived from tissue sodium concentration (TSC) measured by quantitative sodium MRI at 3 Tesla. These near real-time patterns during treatment are compared with overall survival.

EXPERIMENTAL DESIGN

Bioscales were mapped during fractionated chemoradiation therapy in patients with glioblastomas (n = 20) using TSC obtained from serial quantitative sodium MRI at 3 Tesla and a two-compartment model of tissue sodium distribution. The responses of these parameters in newly diagnosed human glioblastomas undergoing treatment were compared with time-to-disease progression and survival.

RESULTS

RTV following tumor resection showed decreased CVF due to disruption of normal cell packing by edema and infiltrating tumor cells. CVF showed either increases back toward normal as infiltrating tumor cells were killed, or decreases as cancer cells continued to infiltrate and extend tumor margins. These highly variable tumor responses showed no correlation with time-to-progression or overall survival.

CONCLUSIONS

These bioscales indicate that fractionated chemoradiotherapy of glioblastomas produces variable responses with low cell killing efficiency. These parameters are sensitive to real-time changes within the treatment volume while remaining stable elsewhere, highlighting the potential to individualize therapy earlier in management, should alternative strategies be available.

Longitudinal MRI findings in patients with newly diagnosed glioblastoma after intraoperative radiotherapy

BACKGROUND AND PURPOSE

Post-radiation treatment effects (pseudoprogression/radionecrosis) may bias MRI-based tumor response evaluation. To understand these changes specifically after high doses of radiotherapy, we analyzed MRIs of patients enrolled in the INTRAGO study (NCT02104882), a phase I/II dose-escalation trial of intraoperative radiotherapy (20-40 Gy) in glioblastoma.

METHODS

INTRAGO patients were evaluated and compared to control patients who received standard therapy with focus on contrast enhancement patterns/volume, T2 lesion volume, and mean rCBV.

RESULTS

Overall, 11/15 (73.3%) INTRAGO patients (median age 60 years) were included. Distant failure was observed in 7/11 (63.6%) patients, local tumor recurrence in one patient (9.1%). On the first follow-up MRI all but one patient demonstrated enhancement of varying patterns around the resection cavity which were: in 2/11 (18.2%) patients thin and linear, in 7/11 (63.6%) combined linear and nodular, and in 1/11 (9.1%) voluminous, indistinct, and mesh-like. In the course of treatment, most patients developed the latter two patterns (8/11 [72.7%]). INTRAGO patients demonstrated more often combined linear and nodular and/or voluminous, indistinct, mesh-like components (8/11 [72.7%]) in comparison to control patients (3/12 [25%], P = 0.02). INTRAGO patients demonstrated significantly increasing enhancing lesion (P = 0.001) and T2 lesion volumes (P < 0.001) in the longitudinal non-parametric analysis in comparison to the control group. rCBV showed no significant differences between both groups.

CONCLUSIONS

High doses of radiotherapy to the tumor cavity result in more pronounced enhancement patterns/volumes and T2 lesion volumes. These results will be useful for the response evaluation of patients exposed to high doses of radiotherapy in future studies.

Re-irradiation for recurrent glioblastoma (GBM): a systematic review and meta-analysis

PURPOSE

To determine the efficacy and toxicity of re-irradiation for patients with recurrent GBM.

MATERIALS AND METHODS

We searched various biomedical databases from 1998 to 2018, for eligible studies where patients were treated with re-irradiation for recurrent GBM. Outcomes of interest were 6 and 12-month overall survival (OS-6, OS-12), 6 and 12-month progression free survival (PFS-6, PFS-12) and serious (Grade 3 +) adverse events (AE). We used the random effects model to pool outcomes across studies and compared pre-defined subgroups using interaction test. Methodological quality of each study was assessed using the Newcastle-Ottawa scoring system.

RESULTS

We found 50 eligible non-comparative studies including 2095 patients. Of these, 42% were of good or fair quality. The pooled results were as follows: OS-6 rate 73% (95% confidence interval (CI) 69-77%), OS-12 rate 36% (95% CI 32-40%), PFS-6 rate 43% (95% CI 35-50%), PFS-12 rate 17% (95% CI 13-20%), and Grade 3 + AE rate 7% (95% CI 4-10%). Subgroup analysis showed that prospective studies reported higher toxicity rates, and studies which utilized brachytherapy to have a longer OS-12. Within the external beam radiotherapy group, there was no dose-response [above or below 36 Gy in 2 Gy equivalent doses (EQD2)]. However, a short fractionation regimen (≤ 5 fractions) seemed to provide superior PFS-6.

CONCLUSION

The available evidence, albeit mostly level III, suggests that re-irradiation provides encouraging disease control and survival rates. Toxicity was not uniformly reported, but seemed to be low from the included studies. Randomized controlled trials (RCT) are needed to establish the optimal management strategy for recurrent GBM.

Intensity Modulated Radiation Therapy Versus Volumetric Arc Radiation Therapy in the Treatment of Glioblastoma-Does Clinical Benefit Follow Dosimetric Advantage?

Purpose

Volumetric modulated arc therapy (VMAT) has been shown by multiple planning studies to hold dosimetric advantages over intensity modulated radiation therapy (IMRT) in the management of brain tumors, including glioblastoma (GBM). Although promising, the clinical impact of these findings has not been fully elucidated.

Methods and Materials

We retrospectively reviewed consecutive patients with a pathologic-confirmed diagnosis of GBM who were treated between 2014 and 2015, a period that encompassed the transition from IMRT to VMAT at a single institution. After surgery, radiation with VMAT consisted of 2 to 3 coplanar arcs with or without an additional noncoplanar arc or IMRT with 5 to 6 gantry angles with concurrent and adjuvant temozolomide. Actuarial analyses were performed using the Kaplan Meier method.

Results

A total of 88 patients treated with IMRT (n = 45) and VMAT (n = 43) were identified. Patients were similar in terms of age, sex, performance status, extent of resection, and the high dose target volume. At a median follow-up time of 27 months (range, .7-32.3 months), the overall survival, freedom from progression, and freedom from new or worsening toxicity rates were not different between the 2 treatment groups (log-rank: P = .33; .87; and .23, respectively). There was no difference in incidences of alopecia, erythema, nausea, worsening or new onset fatigue, or headache during radiation, or temozolomide dose reduction for thrombocytopenia or neutropenia (all P > .05). Patterns of failure were different with more out of field failures in the IMRT group (P = .02). The mean time of treatment (TOT) was significantly reduced by 29% (P < .01) with VMAT (mean TOT: 10.3 minutes) compared with IMRT (mean TOT: 14.6 minutes).

Conclusions

For GBM, treatment with VMAT results in similar oncologic and toxicity outcomes compared with IMRT and may improve resource utilization by reducing TOT. VMAT should be considered a potential radiation modality for patients with GBM.

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.

Photodynamic therapy mediated immune therapy of brain tumors

Photodynamic therapy of tumors requires the topical, systemic or oral administration of a photosensitizing compound, illumination of the tumor area by light of a specific wavelength and the presence of oxygen. Light activation of the photosensitizer transfers energy to molecular oxygen creating singlet oxygen, a highly reactive and toxic species that rapidly reacts with cellular components causing oxidative damage, ultimately leading to cell death. Tumor destruction caused by photodynamic therapy is not only a result of direct tumor cell toxicity via the generation of reactive oxygen species but there is also an immunological and vascular component involved. The immune response to photodynamic therapy has been demonstrated to significantly enhance its efficacy. Depending on a number of factors, including type of photosensitizer, light dose and dose rate, photodynamic therapy has been shown to induce cell death via apoptosis, necrosis, autophagy and in particular immunogenic cell death. It is the purpose of this review to focus mainly on the role photodynamic therapy could play in the generation of specific anti-tumor immunity and vaccines for the treatment of brain tumors.

Genetically-engineered Salmonella typhimurium expressing TIMP-2 as a therapeutic intervention in an orthotopic glioma mouse model

Glioma is one of the most devastating and refractory cancers. The main factors underlying therapeutic failure include extremely invasive characteristics and lack of effective methods for drug delivery. Attenuated Salmonella strains presented a high concentration of tumor targets in various types of cancer models, suggesting a role as potential vectors for drug delivery. In this study, we genetically engineered an attenuated strain of Salmonella as an anti-invasive vector for the targeted delivery and expression of tissue inhibitor of metalloproteinases 2 (TIMP-2) in an orthotopic nude mouse model of glioma. The bioluminescence signals related to tumor size significantly declined in the TIMP-2-expressing Salmonella (SLpTIMP-2)-treated group compared with the control group. Compared with the control group with a survival rate of an average of 33 days, the SLpTIMP-2 group showed an extended survival rate by nearly 60% and lasted an average period of 53 days with TIMP-2 induction. These results indicated the promising therapeutic potential of S. typhimurium for targeted delivery and secretion of TIMP-2 in glioma.

How Histopathologic Tumor Extent and Patterns of Recurrence Data Inform the Development of Radiation Therapy Treatment Volumes in Solid Malignancies

The ability to deliver highly conformal radiation therapy using intensity-modulated radiation therapy and particle therapy provides for new opportunities to improve patient outcomes by reducing treatment-related morbidities following radiation therapy. By reducing the volume of normal tissue exposed to radiation therapy (RT), while also allowing for the opportunity to escalate the dose of RT delivered to the tumor, use of conformal RT delivery should also provide the possibility of expanding the therapeutic index of radiotherapy. However, the ability to safely and confidently deliver conformal RT is largely dependent on our ability to clearly define the clinical target volume for radiation therapy, which requires an in-depth knowledge of histopathologic extent of different tumor types, as well as patterns of recurrence data. In this article, we provide a comprehensive review of the histopathologic and radiographic data that provide the basis for evidence-based guidelines for clinical tumor volume delineation.

Using Smaller-Than-Standard Radiation Treatment Margins Does Not Change Survival Outcomes in Patients with High-Grade Gliomas

PURPOSE

The number of studies that evaluate treatment margins for high grade gliomas (HGG) are limited. We hypothesize that patients with HGG who are treated with a gross tumor volume (GTV) to planning tumor volume (PTV) expansion of ≤1 cm will have progression-free survival (PFS) and overall survival (OS) rates similar to those treated in accordance with standard protocols by the Radiation Therapy Oncology Group or European Organisation for Research and Treatment of Cancer. Furthermore, the PFS and OS of subgroups within the study population will have equivalent survival outcomes with GTV1-to-PTV1 margins of 1.0 cm and 0.4 cm.

METHODS AND MATERIALS

Treatment plans and outcomes for patients with pathologically confirmed HGG were analyzed (n = 267). Survival (PFS and OS) was calculated from the time of the first radiation treatment and a χ² test or Fisher exact test was used to calculate the associations between margin size and patient characteristics. Survival was estimated using Kaplan-Meier and compared using the log-rank test. All analyses were performed on the univariate level.

RESULTS

The median PFS and OS times were 10.6 and 19.1 months, respectively. By disease, the median PFS and OS times were 8.6 and 16.1 months for glioblastoma and 26.7 and 52.5 months for anaplastic glioma. The median follow-up time was 18.3 months. The treatment margin had no effect on outcome and the 1.0 cm GTV1-PTV1 margin subgroup (n = 212) showed median PFS and OS times of 10.7 and 19.1 months, respectively, and the 0.4 cm margin subgroup (n = 55) 10.2 and 19.3 months, respectively. In comparison with the standard treatment with 2 cm to 3 cm margins, there was not a significant difference in outcomes.

CONCLUSIONS

There is no apparent difference in survival when utilizing smaller versus larger margins as defined by the guidelines of the Radiation Therapy Oncology Group and European Organisation for Research and Treatment of Cancer. Although there remains no class I evidence that outcomes after treatment with smaller margins are identical to those after treatment with larger margins, this large series with long-term follow up suggests that a reduction of the margins is safe and further investigation is warranted.

A Prospective 4π Radiation Therapy Clinical Study in Recurrent High-Grade Glioma Patients

PURPOSE

To evaluate the feasibility, safety, dosimetric benefits, delivery efficiency, and patient comfort in the clinical implementation of 4π radiation therapy.

METHODS AND MATERIALS

Eleven patients with recurrent high-grade glioma were recruited for the trial. 4π plans integrating beam orientation and fluence-map optimization were created using an in-house column-generation algorithm. The collision-free beam solution space throughout the 4π steradian was determined using a computer-aided-design model of the Varian TrueBeam system and a human subject. Twenty beams were optimized for each case and imported into Eclipse for intensity modulated radiation therapy planning. Beam orientations with neighboring couch kicks were merged for increased delivery efficiency, generating plans with an average of 16 beam orientations. Volumetric modulated arc therapy (VMAT) plans with 3-4 arcs were also generated for each case, and the plan achieving superior dosimetric quality was selected for treatment. Patient comfort was surveyed after every fraction. Multiple 2-dimensional X-ray images were obtained to measure intrafractional motion.

RESULTS

Of 11 patients, 9 were treated with 4π. Mean and maximum organ at risk doses were equal or significantly lower (P < .05) with 4π than with VMAT. Particularly substantial dose reduction of 2.92 Gy in the average accumulated brainstem maximum dose enabled treatments that would otherwise not satisfy safe dose constraints with VMAT. One patient was not treated because neither plan met the dosimetric criteria. The other was treated with VMAT owing to comparable dosimetry resulting from a planning target volume located in a separate co-plane superior to organs at risk. Treatments were well tolerated, with an average patient comfort score of 8.6/10. Intrafractional motion was <1.5 mm for all delivered fractions, and the average delivery time was 34.1 minutes.

CONCLUSIONS

The feasibility, safety, dosimetric benefits, delivery efficiency, and patient comfort of 4π radiation therapy have been clinically demonstrated with a prospective clinical trial. The results elucidate the potential and challenges of wider clinical implementations.

Primary Glioblastoma Multiforme in Younger Patients: A Single-institution Experience

Aims and Background

To report our experience of patients with primary glioblastoma multiforme of young age by evaluating the characteristics, prognostic factors, and treatment outcomes.

Patients and Methods

Seventy patients with primary glioblastoma multiforme (GBM) treated at our department between 1996 and 2004 were studied. The male-female ratio was 2.6:1. The median age was 53 (16-74). Sixty-eight patients (97%) were operated on before radiotherapy and 2 patients (3%) underwent only stereotactic biopsy. All patients received radiotherapy. Postoperative chemotherapy as an adjuvant to radiotherapy was given to 9 patients (12%). The patients were divided into 2 groups according to their age (group A ≤35 years, n = 21 vs group B >35 years, n = 49). Survival was determined with the Kaplan-Meier method and differences were compared using the log-rank test. Cox regression analysis was performed to identify the independent prognostic factors. Karnofsky performance status (≥70 vs <70), age (≤35 vs >35 years), gender, tumor size (≤4 vs >4 cm), number of involved brain lobes (1 vs more than 1), type of surgery (total vs subtotal), preoperative seizure history (present vs absent), radiotherapy field (total cranium vs partial), total radiotherapy dose (60 vs 66 Gy), and adjuvant chemotherapy (present vs absent) were evaluated in univariate analysis.

Results

The median survival was 10.3 months in the whole group, 19.5 months in the younger age group and 5.7 months in the older age group. During follow-up re-craniotomy was performed in 2 patients (3%), and 1 patient (1%) developed spinal seeding metastases and was given spinal radiotherapy. In univariate analysis younger age vs older age: median 19.5 months vs 5.27 months (P = 0.0012); Karnofsky performance status ≥70 vs <70: median 15.3 months vs 2.67 months (P <0.0001), and external radiotherapy dose 60 Gy vs 66 Gy: median 11.6 months vs 3 months (P = 0.02) were found as significant prognostic factors for survival. In regression analysis a worse performance status (KPS <70) was found to be the only independent factor for survival (P = 0.014, 95% CI HR = 0.0043 [0.0001-0.15]).

Conclusions

Younger patients with primary glioblastoma multiforme had a relatively long survival (median, 19.5 months, with a 2-year survival rate of 30%) compared to older patients. This was due particularly to their better performance status.

Clinical Results of Unconventional Fractionation Radiotherapy in Central Nervous System Tumors

Malignant brain tumors (primary and metastatic) are apparently resistant to most therapeutic efforts. Several randomized trials have provided evidence supporting the efficacy of radiation therapy. Attempts at improving the results of external beam radiotherapy include altered fractionation, radiation sensitizers and concomitant chemotherapy. In low-grade gliomas, all clinical studies with radiotherapy have employed conventional dose fractionation regimens. In high-grade gliomas, hypofractionation schedules represent effective palliative regimens in poor prognosis subsets of patients; short-term survival in these patients has not allowed to evaluate late toxicity. In tumors arising within the central nervous system, hyperfractionated irradiation exploits the differences in repair capacity between tumour and late responding normal tissues. It may allow for higher total dose and may result in increased tumor cell kill. Accelerated radiotherapy may reduce the repopulation of tumor cells between fractions. It may potentially improve tumor control for a given dose level, provided that there is no increase in late normal tissue injury. In supratentorial malignant gliomas, superiority of accelerated hyperfractionated over conventionally fractionated schedules was observed in a randomized trial; however, the gain in survival was less than 6 months. At present no other randomized trial supports the preferential choice for altered fractionation irradiation. Also in pediatric brainstem tumors there are no data to confirm the routine use of hyperfractionated irradiation, and significant late sequelae have been reported in the few long-term survivors. Shorter treatment courses with accelerated hyperfractionated radiotherapy may represent a useful alternative to conventional irradiation for the palliation of brain metastases. Different considerations have been proposed to explain this gap between theory and clinical data. Patients included in dose/effect studies are not stratified by prognostic factors and other treatment-related parameters. This observation precludes any definite conclusion about the relative role of conventional and of altered fractionation. New approaches are currently in progress. More prolonged radiation treatments, up to higher total doses, could delay time to tumor progression and improve survival in good prognosis subsets of patients; altered fractionation may be an effective therapeutic tool to achieve this goal.

Irradiation Fields and Doses in Glioblastoma Multiforme: Are Current Standards Adequate?

Aims and background

The optimum conventional radiotherapy in glioblastoma multiforme patients has not been clearly defined by prospective trials. To better characterize a standard radiotherapy in glioblastoma multiforme, the impact on survival of different fields and doses was analyzed in a retrospective single center series.

Methods

One hundred and forty-seven patients with glioblastoma multiforme, submitted to biopsy only (n = 15), subtotal (n = 48) or total resection (n = 82) and who completed the planned postsurgical radiotherapy, were considered. The median age was 57 years, the male/female ratio 1.5/1, and the performance status ≥70 in 76%. Whole brain irradiation, followed by a boost to partial brain, was used in 75 cases with a whole brain dose of 44–50 Gy (median, 46) and a partial brain dose of 56–70 Gy (median, 60 Gy). Partial brain irradiation alone was used in 72 patients with a dose of 56–70 Gy (median, 61 Gy). Ninety-eight patients received 56–60 Gy (median, 59 Gy) to partial brain whereas 49 patients received 61–70 Gy (median, 63 Gy).

Results

There was an almost significantly longer survival in patients irradiated to the partial brain alone with respect to those also receiving whole brain radiotherapy (P = 0.056). Doses <60 Gy significantly prolonged survival (P = 0.006). Multivariate analysis confirmed that the impact on survival of radiation dose was independent of age, performance status, extent of surgery, field of irradiation and the use of chemotherapy. The extent of irradiation field was not independently related to improved survival.

Conclusions

Our retrospective findings suggest that we reflect on the adequacy of the current standard irradiation parameters. Well-designed prospective trials are necessary to standardize the radiotherapy control group in patients with glioblastoma multiforme to be compared in phase III trials with innovative therapeutic approaches.

Hypoxia activates enhanced invasive potential and endogenous hyaluronic acid production by glioblastoma cells

Glioblastoma (GBM) is the most common, aggressive, and deadly form of adult brain cancer, and is associated with a short survival rate (median 12-15 months, 5+ year less than 5%). The complex tumor microenvironment includes matrix transitions at the tumor margin, such as gradations in hyaluronic acid (HA). In addition, metabolic stress induced by decreased oxygen content across the tumor may contribute to tumor progression. However, cross-talk between matrix composition and metabolic stress remains unclear. In this study, we fabricated an in vitro brain memetic HA-decorated gelatin hydrogel platform incorporating variable oxygen concentrations to mimic intra-tumoral hypoxia. We observed that EGFR status (wildtype vs. a constitutively active EGFRvIII mutant) of U87 GBM cells affected proliferation and metabolic activity in response to hypoxia and matrix-bound HA. The use of an invasion assay revealed that invasion was significantly enhanced in both cell types under hypoxia. Moreover, we observed compensatory secretion of soluble HA in cases of enhanced GBM cell invasion, consistent with our previous findings using other GBM cell lines. Interestingly, U87 GBM cells adapted to hypoxia by shifting toward a more anaerobic metabolic state, a mechanism that may contribute to GBM cell invasion. Collectively, these data demonstrate that the use of a three-dimensional hydrogel provides a robust method to study the impact of matrix composition and metabolic challenges on GBM cell invasion, a key factor contributing to the most common, aggressive, and deadly form of adult brain cancer.

Location of subventricular zone recurrence and its radiation dose predicts survival in patients with glioblastoma

Glioblastomas are aggressive brain tumors that frequently recur in the subventricular zone (SVZ) despite maximal treatment. The purpose of this study was to evaluate imaging patterns of subventricular progression and impact of recurrent subventricular tumor involvement and radiation dose to patient outcome. Retrospective review of 50 patients diagnosed with glioblastoma and treated with surgery, radiation, and concurrent temozolomide from January 2012 to June 2013 was performed. Tumors were classified based on location, size, and cortical and subventricular zone involvement. Survival was compared based on recurrence type, distance from the initial enhancing tumor (local ≤ 2 cm, distant > 2 cm), and the radiation dose at the recurrence site. Progression of enhancing subventricular tumor was common at both local (58%) and distant (42%) sites. Median survival was better after local SVZ recurrence than distant SVZ recurrence (8.7 vs. 4.3 months, p = 0.04). Radiation doses at local SVZ recurrence sites recurrence averaged 57.0 ± 4.0 Gy compared to 44.7 ± 6.7 Gy at distant SVZ recurrence sites (p = 0.008). Distant subventricular progression at a site receiving ≤ 45 Gy predicted worse subsequent survival (p = 0.05). Glioblastomas frequently recurred in the subventricular zone, and patient survival was worse when enhancing tumor occurred at sites that received lower radiation doses. This recurrent disease may represent disease undertreated at the time of diagnosis, and further study is needed to determine if improved treatment strategies, such as including the subventricular zone in radiation fields, could improve clinical outcomes.

Utilizing 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) to define suspected nonenhancing tumor for radiation therapy planning of glioblastoma

AIM

The authors sought to evaluate the impact of 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) on radiation therapy planning for patients diagnosed with glioblastoma (GBM) and the presence of suspected nonenhancing tumors compared with standard magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Patients with GBM and contrast-enhanced MRI scans showing regions suspicious of nonenhancing tumor underwent postoperative FET-PET before commencing radiation therapy. Two clinical target volumes (CTVs) were created using pre- and postoperative MRI: MRI fluid-attenuated inversion recovery (FLAIR) sequences (CTV_FLAIR) and MRI contrast sequences with an expansion on the surgical cavity (CTV_Sx). FET-PET was used to create biological tumor volumes (BTVs) by encompassing FET-avid regions, forming BTV_FLAIR and BTV_Sx. Volumetric analyses were conducted between CTVs and respective BTVs using Wilcoxon signed-rank tests. The volume increase with addition of FET was analyzed with respect to BTV_FLAIR and BTV_Sx. Presence of focal gadolinium contrast enhancement within previously nonenhancing tumor or within the FET-avid region was noted on MRI scans at 1 and 3 months after radiation therapy.

RESULTS

Twenty-six patients were identified retrospectively from our database, of whom 24 had demonstrable FET uptake. The median CTV_FLAIR, CTV_Sx, BTV_FLAIR, and BTV_Sx were 57.1 mL (range, 1.1-217.4), 83.6 mL (range, 27.2-275.8), 62.8 mL (range, 1.1-307.3), and 94.7 mL (range, 27.2-285.5), respectively. When FET-PET was used, there was a mean increase in volume of 26.8% from CTV_FLAIR to BTV_FLAIR and 20.6% from CTV_Sx to BTV_Sx. A statistically significant difference was noted on Wilcoxon signed-rank test when assessing volumetric change between CTV_FLAIR and BTV_FLAIR (P < .0001) and CTV_Sx and BTV_Sx (P < .0001). Six of 24 patients (25%) with FET avidity before radiation therapy showed focal gadolinium enhancement within the radiation therapy portal.

CONCLUSIONS

FET-PET may help improve delineation of GBM in cases with a suspected nonenhancing component. This may result in improved radiation therapy target delineation and reduce the risk of potential geographical miss.

SUMMARY

We investigated the impact of 18F-fluoroethyltyrosine (FET) positron emission tomography (PET) on radiation therapy planning for patients diagnosed with glioblastoma (GBM) and a suspected nonenhancing tumor compared with standard magnetic resonance imaging. We performed volumetric analyses between clinical target volumes and respective biological target volumes using Wilcoxon signed-rank tests. FET-PET may help improve delineation of GBM in cases with a suspected nonenhancing component and reduce the risk of potential geographical miss.

Galectin-1 is a poor prognostic factor in patients with glioblastoma multiforme after radiotherapy

Background

Galectin-1, a radioresistance marker, was found in our previous study to be a prognostic factor for cervical cancer. The aim of current study is to determine the prognostic significance of the galectin-1 expression level in patients with glioblastoma multiforme (GBM) undergoing adjuvant radiotherapy (RT).

Methods

We included 45 patients with GBM who were treated with maximal safe surgical resection or biopsy alone followed by adjuvant RT of EQD2 (equivalent dose in 2-Gy fractions) > or = 60 Gy for homogeneous treatment. Paraffin-embedded tissues acquired from the Department of Pathology were analyzed using immunohistochemical staining for galectin-1 expression. The primary endpoint was overall survival (OS).

Results

Patients with weak expression had a better median survival (27.9 months) than did those with strong expression (10.7 months; p = 0.009). We compared characteristics between weak and strong galectin-1 expression, and only the expression level of galectin-3 showed a correlation. The group with weak galectin-1 expression displayed a 3-year OS of 27.3% and a 3-year cancer-specific survival (CSS) of 27.3%; these values were only 5.9% and 7.6%, respectively, in the group with strong galectin-1 expression (p = 0.009 and 0.020, respectively). Cox regression was used to confirm that the expression level of galectin-1 (weak vs. strong) is a significant factor of OS (p = 0.020) and CSS (p = 0.022). Other parameters, such as the expression level of galectin-3, Eastern Cooperative Oncology Group (ECOG) performance, gender, surgical method, age ≥ 50 years, tumor size, or radiation field were not significant factors.

Conclusion

The expression level of galectin-1 affects survival in patients with GBM treated with adjuvant RT. Future studies are required to analyze the effect of other factors, such as O(6)-methylguanine-DNA methyltransferase (MGMT)-promoter methylation status, in patients with weak and strong galectin-1 expression.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4025-2) contains supplementary material, which is available to authorized users.

Evaluation of Helical Tomotherapy in the Treatment of High-Grade Gliomas near Critical Structures

Background

Our purpose was to investigate the role of helical tomotherapy using a simultaneous integrated boost technique for the treatment of high-grade gliomas near intracranial critical structures.

Methods and materials

Of 27 patients treated with helical tomotherapy, 11 were eligible. Only patients whose tumors were within 0.5 cm of the optic chiasm, the optic nerve or the brainstem were included. The therapeutic approach was a simultaneous integrated boost, prescribing 66 and 60 Gy to the PTV1 and PTV2, respectively, in 30 fractions. All patients received concomitant temozolomide at a dose of 75 mg/m2 daily during radiation therapy.

Results

Of the 11 patients considered, 3 patients (27%) died after 4 months from the completion of the combined treatment. Three patients (27%) presented local progression, and the median time to disease progression was 6 months (range, 1–12). Five patients (45%), at the time of this evaluation, did not have signs or symptoms of recurrence or progression of the disease. Acute toxicity, evaluated during radiochemotherapy, was minimal, with all patients experiencing RTOG grade 0 and grade 1 toxicity.

Conclusions

Helical tomotherapy proved to be an effective and safe treatment modality, with an improvement of accuracy in delivery of highdose radiotherapy despite the presence of nearby critical structures.

Treatment of Recurrent Glioblastoma with Stereotactic Radiotherapy: Long-Term Results of a Mono-Institutional Trial

Aims and background

Few clinical data exist concerning normal brain tissue tolerance to re-irradiation. The present study evaluated long-term outcome of 22 recurrent glioblastoma patients re-irradiated with radiosurgery or fractionated stereotactic radiotherapy.

Methods

Twenty-two patients were treated with radiosurgery (13, 59%) or fractionated stereotactic radiotherapy (9, 41%) for 24 lesions of recurrent glioblastoma. The male/female ratio was 14: 8, median age 55 years (range, 27–81), and median Karnofsky performance status 90 (range, 70–100). The majority of the cases (77%) was in recursive partitioning analysis classes III or IV. Radiosurgery or fractionated stereotactic radiotherapy was chosen according to lesion size and location.

Results

Median time between primary radiotherapy and re-irradiation was 9 months. Median doses were 17 Gy and 30 Gy, whereas median cumulative normalized total dose was 141 Gy and 98 Gy for radiosurgery and fractionated stereotactic radiotherapy, respectively. All patients submitted to radiosurgery had a cumulative normalized total dose of more than 100 Gy, whereas only a few (44%) of fractionated stereotactic radiotherapy patients had a cumulative normalized total dose exceeding 100 Gy. Median follow-up from re-irradiation was 54 months. At the time of analysis, all patients had died. After re-irradiation, 1 (4%) lesion was in partial remission, 16 (67%) lesions were stable, and the remaining 7 (29%) were in progression. Median duration of response was 6 months, and median survival from re-irradiation 11 months. Three of 13 (23%) patients submitted to radiosurgery developed asymptomatic brain radionecrosis. The cumulative normalized total dose for the 3 patients was 122 Gy, 124 Gy, and 141 Gy, respectively. In one case, the volume of the lesion was large (14 cc), and in the other 2 the interval between the first and second cycle of radiotherapy was short (5 months).

Conclusions

Re-irradiation with radiosurgery and fractionated stereotactic radiotherapy is feasible and effective in recurrent glioblastoma patients. Apart from the importance of an accurate patient selection, cumulative radiotherapy dose and a correct indication for radiosurgery or fractionated stereotactic radiotherapy must be taken into account to avoid brain toxicity. Free full text available at www.tumorionline.it

Relationship between Glioblastoma Dose Volume Parameters Measured by Dual Time Point Fluoroethylthyrosine-PET and Clinical Outcomes

Glioblastoma multiforme (GBM) is highly invasive. Despite irradiation with wide margins, GBM usually recurs in-field. Recent in vitro data have suggested that progression might be promoted by sublethal irradiation. Fluoroethylthyrosine-PET (FET-PET) can be used to detect glioblastoma invasion not apparent on MRI. We therefore performed a retrospective analysis of a prospective clinical study to examine whether glioblastoma outcomes depend on dose volume parameters measured by MRI and FET-PET. Twenty-three patients were prospectively recruited to a study examining the role of dual time point FET-PET in the treatment planning of GBM radiotherapy. The dose delivered to the site of recurrence was subdivided into suboptimal-dose (SOD) and high-dose (HD) areas. Types of progression were defined for correlation with dosimetric parameters including V100% of gross tumor volume (GTV)_PET, GTV_PETMRI, and GTV_MRI. The HD area did not cover the entire GTV_PETMRI in any case. Recurrences were significantly more frequent in the SubD area (chi-squared test, p = 0.004). There was no relationship between increasing dose volume and progression. The V100% for GTV_PET and progression-free survival (PFS) was positively correlated (Spearman’s rho 0.417; p = 0.038). Progression is more common in areas with suboptimal dosing. Dose heterogeneity within GTV_PET may be responsible for shorter PFS.

Recurrence patterns after maximal surgical resection and postoperative radiotherapy in anaplastic gliomas according to the new 2016 WHO classification

We assessed the appropriateness of current radiotherapy volume for WHO grade III gliomas. The records of 73 patients with WHO grade III gliomas who received postoperative radiotherapy between 2001 and 2013 were retrospectively reviewed. Based on the 2016 WHO classification, 25/73 (34.2%) patients had anaplastic oligodendroglioma (AO), IDH-mutant and 1p/19q-codeleted; 11/73 (15.1%) patients had anaplastic astrocytoma, IDH-mutant; and 37/73 (50.7%) patients had anaplastic astrocytoma, IDH-wildtype. The extent of resection (EOR) was total in 43 patients (58.9%). The median follow-up time was 84 months. The 5-year overall survival was 65.4%. Of 31 patients with documented recurrences, 20 (64.5%) had infield gross tumor volume (GTV) failure, six (19.4%) had clinical target volume (CTV)/marginal failure, and five (16.1%) had outfield failure/seeding. In 13 recurrences among 43 patients who underwent gross total resection (GTR), six (46.2%) had infield CTV/marginal failure. However, among 30 patients for whom GTR was not conducted, infield GTV failure was dominant (77.8%). Seventeen patients with AO, IDH-mutant and 1p/19q-codeleted who underwent GTR experienced no recurrence. In conclusion, maximal surgical resection and postoperative radiotherapy resulted in a favorable prognosis, especially in patients with GTR, IDH mutation, and 1p/19q codeletion. Patterns of failure differed by EOR.

From imaging to biology of glioblastoma: new clinical oncology perspectives to the problem of local recurrence

GBM is one of the most common and aggressive brain tumors. Surgery and adjuvant chemoradiation have succeeded in providing a survival benefit. Although most patients will eventually experience local recurrence, the means to fight recurrence are limited and prognosis remains poor. In a disease where local control remains the major challenge, few trials have addressed the efficacy of local treatments, either surgery or radiation therapy. The present article reviews recent advances in the biology, imaging and biomarker science of GBM as well as the current treatment status of GBM, providing new perspectives to the problem of local recurrence.

Prospective trial evaluating the sensitivity and specificity of 3,4-dihydroxy-6-[18F]-fluoro-L-phenylalanine (18F-DOPA) PET and MRI in patients with recurrent gliomas

Treatment-related changes can be difficult to differentiate from progressive glioma using MRI with contrast (CE). The purpose of this study is to compare the sensitivity and specificity of 18F-DOPA-PET and MRI in patients with recurrent glioma. Thirteen patients with MRI findings suspicious for recurrent glioma were prospectively enrolled and underwent 18F-DOPA-PET and MRI for neurosurgical planning. Stereotactic biopsies were obtained from regions of concordant and discordant PET and MRI CE, all within regions of T2/FLAIR signal hyperintensity. The sensitivity and specificity of 18F-DOPA-PET and CE were calculated based on histopathologic analysis. Receiver operating characteristic curve analysis revealed optimal tumor to normal (T/N) and SUVmax thresholds. In the 37 specimens obtained, 51% exhibited MRI contrast enhancement (M+) and 78% demonstrated 18F-DOPA-PET avidity (P+). Imaging characteristics included M-P- in 16%, M-P+ in 32%, M+P+ in 46% and M+P- in 5%. Histopathologic review of biopsies revealed grade II components in 16%, grade III in 43%, grade IV in 30% and no tumor in 11%. MRI CE sensitivity for recurrent tumor was 52% and specificity was 50%. PET sensitivity for tumor was 82% and specificity was 50%. A T/N threshold > 2.0 altered sensitivity to 76% and specificity to 100% and SUVmax > 1.36 improved sensitivity and specificity to 94 and 75%, respectively. 18F-DOPA-PET can provide increased sensitivity and specificity compared with MRI CE for visualizing the spatial distribution of recurrent gliomas. Future studies will incorporate 18F-DOPA-PET into re-irradiation target volume delineation for RT planning.

A combined diffusion tensor imaging and Ki-67 labeling index study for evaluating the extent of tumor infiltration using the F98 rat glioma model

Diffusion tensor imaging (DTI) has been proven to be a sophisticated and useful tool for the delineation of tumors. In the present study, we investigated the predictive role of DTI compared to other magnetic resonance imaging (MRI) techniques in combination with Ki-67 labeling index in defining tumor cell infiltration in the peritumoral regions of F98 glioma-bearing rats. A total of 29 tumor-bearing Fischer rats underwent T2-weighted imaging, contrast-enhanced T1-weighted imaging, and DTI of their brain using a 7.0-T MRI scanner. The fractional anisotropy (FA) ratios were correlated to the Ki-67 labeling index using the Spearman correlation analysis. A receiver operating characteristic curve (ROC) analysis was established to evaluate parameters with sensitivity and specificity in order to identify the threshold values for predicting tumor infiltration. Significant correlations were observed between the FA ratios and Ki-67 labeling index (r = - 0.865, p < 0.001). The ROC analysis demonstrated that the apparent diffusion coefficient (ADC) and FA ratios could predict 50% of the proliferating cells in the regions of interest (ROI), with a sensitivity of 88.1 and 81.3%, and a specificity of 86.2 and 90.2%, respectively (p < 0.001). Meanwhile, the two ratios could also predict 10% of the proliferating cells in the ROI, with a sensitivity of 82.5 and 94.9%, and a specificity of 100 and 88.9%, respectively (p < 0.001). The present study demonstrated that the FA ratios are closely correlated with the Ki-67 labeling index. Furthermore, both ADC and FA ratios, derived from DTI, were useful for quantitatively predicting the Ki-67 labeling of glioma cells.

Prognostication of Survival Outcomes in Patients Diagnosed with Glioblastoma

OBJECTIVE

Glioblastoma multiforme (GBM) is an aggressive primary brain tumor with dismal survival. This study aims to examine the prognostic value of primary tumor sites and race on survival outcomes.

METHODS

Patient data obtained from the Scott and White Hospital Brain Tumor Registry (1976-2013) were stratified according to sex, age, race, primary tumor site, vital status, and survival.

RESULTS

Of the 645 patients, 580 (89.9%) were diagnosed with GBM not otherwise specified (GBM NOS), 57 (8.8%) with GBM, and 8 (1.2%) with giant-cell GBM. Most were male (53.5%), aged 50 years or older (78.7%). The white population had the highest GBM prevalence (87.1%) and the lowest overall survival versus all other race groups (6.6% vs. 30.1%; P < 0.01). The black population had a relatively low prevalence of GBM (5.9%) and the greatest overall survival versus all others (47.4% vs. 7.3%; P < 0.01). Primary tumor sites located in the temporal (25.8% vs. 20.2%; P = 0.03), occipital (8.1% vs. 2.9%; P = 0.05), and parietal lobes (24.2% vs. 20.8%; P = 0.05) had a greater occurrence in surviving individuals. The overall survival for men versus women was (62.9% vs. 37.1%; P = 0.12).

CONCLUSIONS

Black racial background and temporal, occipital, or parietal primary tumor sites are suggestive of positive survival outcomes. Conversely, white racial background with primary tumor sites in the brain overlapping and NOS areas seem to be associated with negative outcomes and decreased survival. Thus, racial background and primary tumor site may be useful prognostic factors in patients with GBM.

Impact on Radiation Dose and Volume V57 Gy of the Brain on Recurrence and Survival of Patients with Glioblastoma Multiformae

BACKGROUND

The aim of the study was to analyze impact of irradiated brain volume V57 Gy (volume receiving 57 Gy and more) on time to progression and survival of patients with glioblastoma.

PATIENTS AND METHODS

Dosimetric analysis of treatment plan data has been performed on 70 patients with glioblastoma, treated with postoperative radiochemotherapy with temozolomide, followed by adjuvant temozolomide. Patients were treated with 2 different methods of definition of treatment volumes and prescription of radiation dose. First group of patients has been treated with one treatment volume receiving 60 Gy in 2 Gy daily fraction (31 patients) and second group of the patients has been treated with "cone-down" technique, which consisted of two phases of treatment: the first phase of 46 Gy in 2 Gy fraction followed by "cone-down" boost of 14 Gy in 2 Gy fraction (39 patients). Quantification of V57 Gy and ratio brain volume/V57Gy has been done. Average values of both parameters have been taken as a threshold value and patients have been split into 2 groups for each parameter (values smaller/ lager than threshold value).

RESULTS

Mean value for V57 Gy was 593.39 cm3 (range 166.94 to 968.60 cm3), mean value of brain volume has was 1332.86 cm3 (range 1047.00 to 1671.90 cm3) and mean value of brain-to-V57Gy ratio was 2.46 (range 1.42 to 7.67). There was no significant difference between two groups for both V57 Gy and ratio between brain volume and V57 Gy.

CONCLUSIONS

Irradiated volume with dose 57 Gy or more (V57 Gy) and ration between whole brain volume and 57 Gy had no impact on time to progression and survival of patients with glioblastoma.

BICD1 expression, as a potential biomarker for prognosis and predicting response to therapy in patients with glioblastomas

There is variation in the survival and therapeutic outcome of patients with glioblastomas (GBMs). Therapy resistance is an important challenge in the treatment of GBM patients. The aim of this study was to identify Temozolomide (TMZ) related genes and confirm their clinical relevance. The TMZ-related genes were discovered by analysis of the gene-expression profiling in our cell-based microarray. Their clinical relevance was verified by in silico meta-analysis of the Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) datasets. Our results demonstrated that BICD1 expression could predict both prognosis and response to therapy in GBM patients. First, high BICD1 expression was correlated with poor prognosis in the TCGA GBM cohort (n=523) and in the CGGA glioma cohort (n=220). Second, high BICD1 expression predicted poor outcome in patients with TMZ treatment (n=301) and radiation therapy (n=405). Third, multivariable Cox regression analysis confirmed BICD1 expression as an independent factor affecting the prognosis and therapeutic response of TMZ and radiation in GBM patients. Additionally, age, MGMT and BICD1 expression were combinedly utilized to stratify GBM patients into more distinct risk groups, which may provide better outcome assessment. Finally, we observed a strong correlation between BICD1 expression and epithelial-mesenchymal transition (EMT) in GBMs, and proposed a possible mechanism of BICD1-associated survival or therapeutic resistance in GBMs accordingly. In conclusion, our study suggests that high BICD1 expression may result in worse prognosis and could be a predictor of poor response to TMZ and radiation therapies in GBM patients.

Diffusion tensor magnetic resonance imaging driven growth modeling for radiotherapy target definition in glioblastoma

BACKGROUND

The clinical target volume (CTV) in radiotherapy is routinely based on gadolinium contrast enhanced T1 weighted (T1w + Gd) and T2 weighted fluid attenuated inversion recovery (T2w FLAIR) magnetic resonance imaging (MRI) sequences which have been shown to over- or underestimate the microscopic tumor cell spread. Gliomas favor spread along the white matter fiber tracts. Tumor growth models incorporating the MRI diffusion tensors (DTI) allow to account more consistently for the glioma growth. The aim of the study was to investigate the potential of a DTI driven growth model to improve target definition in glioblastoma (GBM).

MATERIAL AND METHODS

Eleven GBM patients were scanned using T1w, T2w FLAIR, T1w + Gd and DTI. The brain was segmented into white matter, gray matter and cerebrospinal fluid. The Fisher-Kolmogorov growth model was used assuming uniform proliferation and a difference in white and gray matter diffusion of a ratio of 10. The tensor directionality was tested using an anisotropy weighting parameter set to zero (γ0) and twenty (γ20). The volumetric comparison was performed using Hausdorff distance, Dice similarity coefficient (DSC) and surface area.

RESULTS

The median of the standard CTV (CTVstandard) was 180 cm³. The median surface area of CTVstandard was 211 cm². The median surface area of respective CTV_γ0 and CTV_γ20 significantly increased to 338 and 376 cm², respectively. The Hausdorff distance was greater than zero and significantly increased for both CTV_γ0 and CTV_γ20 with respective median of 18.7 and 25.2 mm. The DSC for both CTV_γ0 and CTV_γ20 were significantly below one with respective median of 0.74 and 0.72, which means that 74 and 72% of CTVstandard were included in CTV_γ0 and CTV_γ20, respectively.

CONCLUSIONS

DTI driven growth models result in CTVs with a significantly increased surface area, a significantly increased Hausdorff distance and decreased overlap between the standard and model derived volume.

Indications and Efficacy of Gamma Knife Stereotactic Radiosurgery for Recurrent Glioblastoma: 2 Decades of Institutional Experience

BACKGROUND

The role of stereotactic radiosurgery (SRS) for recurrent glioblastoma and the radionecrosis risk in this setting remain unclear.

OBJECTIVE

To perform a large retrospective study to help inform proper indications, efficacy, and anticipated complications of SRS for recurrent glioblastoma.

METHODS

We retrospectively analyzed patients who underwent Gamma Knife SRS between 1991 and 2013. We used the partitioning deletion/substitution/addition algorithm to identify potential predictor covariate cut points and Kaplan-Meier and proportional hazards modeling to identify factors associated with post-SRS and postdiagnosis survival.

RESULTS

One hundred seventy-four glioblastoma patients (median age, 54.1 years) underwent SRS a median of 8.7 months after initial diagnosis. Seventy-five percent had 1 treatment target (range, 1-6), and median target volume and prescriptions were 7.0 cm 3 (range, 0.3-39.0 cm 3 ) and 16.0 Gy (range, 10-22 Gy), respectively. Median overall survival was 10.6 months after SRS and 19.1 months after diagnosis. Kaplan-Meier and multivariable modeling revealed that younger age at SRS, higher prescription dose, and longer interval between original surgery and SRS are significantly associated with improved post-SRS survival. Forty-six patients (26%) underwent salvage craniotomy after SRS, with 63% showing radionecrosis or mixed tumor/necrosis vs 35% showing purely recurrent tumor. The necrosis/mixed group had lower mean isodose prescription compared with the tumor group (16.2 vs 17.8 Gy; P = .003) and larger mean treatment volume (10.0 vs 5.4 cm 3 ; P = .009).

CONCLUSION

Gamma Knife may benefit a subset of focally recurrent patients, particularly those who are younger with smaller recurrences. Higher prescriptions are associated with improved post-SRS survival and do not seem to have greater risk of symptomatic treatment effect.

Zika virus has oncolytic activity against glioblastoma stem cells

Glioblastoma is a highly lethal brain cancer that frequently recurs in proximity to the original resection cavity. We explored the use of oncolytic virus therapy against glioblastoma with Zika virus (ZIKV), a flavivirus that induces cell death and differentiation of neural precursor cells in the developing fetus. ZIKV preferentially infected and killed glioblastoma stem cells (GSCs) relative to differentiated tumor progeny or normal neuronal cells. The effects against GSCs were not a general property of neurotropic flaviviruses, as West Nile virus indiscriminately killed both tumor and normal neural cells. ZIKV potently depleted patient-derived GSCs grown in culture and in organoids. Moreover, mice with glioblastoma survived substantially longer and at greater rates when the tumor was inoculated with a mouse-adapted strain of ZIKV. Our results suggest that ZIKV is an oncolytic virus that can preferentially target GSCs; thus, genetically modified strains that further optimize safety could have therapeutic efficacy for adult glioblastoma patients.

Development of an integrated Monte Carlo model for glioblastoma multiforme treated with boron neutron capture therapy

Glioblastomas (GBM) are notorious for their high fatality rate. Boron Neutron Capture Therapy (BNCT) being a biochemically targeted type of radiotherapy is a potent modality for GBM. In the current work, a BNCT treatment modelling framework for GBM was developed. Optimal Clinical Target Volume (CTV) margins for GBM-BNCT and the BNCT efficacy have been investigated. The model integrated a cell-based dosimetry model, an in-house-developed epithermal neutron beam model and previously-developed Microscopic Extension Probability (MEP) model. The system was defined as a cubic ICRP-brain phantom divided into 20 μm side voxels. The corresponding ¹⁰B concentrations in GBM and normal brain cells were applied. The in-silico model was irradiated with the epithermal neutron beam using 2 and 2.5 cm CTV margins. Results from the cell-based dosimetry and the MEP models were combined to calculate GBM cell survival fractions (SF) post BNCT and compared to x-ray radiotherapy (XRT) SFs. Compared to XRT, the SF within the beam decreased by five orders of magnitudes and the total SF was reduced three times following BNCT. CTV extension by 0.5 cm reduced the SF by additional (53.8 ± 0.3)%. In conclusion, BNCT results in a more efficient cell kill. The extension of the CTV margin, however, may not increase the treatment outcome significantly.

Thermoresponsive nanocomposite gel for local drug delivery to suppress the growth of glioma by inducing autophagy

Although the treatments of malignant glioma include surgery, radiotherapy and chemotherapy by oral drug administration, the prognosis of patients with glioma remains very poor. We developed a polyethylene glycol-dipalmitoylphosphatidyle- thanoiamine (mPEG-DPPE) calcium phosphate nanoparticles (NPs) injectable thermoresponsive hydrogel (nanocomposite gel) that could provide a sustained and local delivery of paclitaxel (PTX) and temozolomide (TMZ). In addition, the proportion of PTX and TMZ for the optimal synergistic antiglioma effect on C6 cells was determined to be 1:100 (w/w) by the Chou and Talalay method. Our results clearly indicated that the autophagy induced by PTX:TMZ NPs plays an important role in regulating tumor cell death, while autophagy inhibition dramatically reverses the antitumor effect of PTX:TMZ NPs, suggesting that antiproliferative autophagy occurs in response to PTX:TMZ NPs treatment. The antitumor efficacy of the PTX:TMZ NP-loaded gel was evaluated in situ using C6 tumor-bearing rats, and the PTX:TMZ NP-loaded gel exhibited superior antitumor performance. The antitumor effects of the nanocomposite gel in vivo were shown to correlate with autophagic cell death in this study. The in vivo results further confirmed the advantages of such a strategy. The present study may provide evidence supporting the development of nanomedicine for potential clinical application.

Cerebrospinal fluid dissemination of high-grade gliomas following boron neutron capture therapy occurs more frequently in the small cell subtype of IDH1R132H mutation-negative glioblastoma

We have used boron neutron capture therapy (BNCT) to treat patients in Japan with newly diagnosed or recurrent high-grade gliomas and have observed a significant increase in median survival time following BNCT. Although cerebrospinal fluid dissemination (CSFD) is not usually seen with the current standard therapy of patients with glioblastoma (GBM), here we report that subarachnoid or intraventricular CSFD was the most frequent cause of death for a cohort of our patients with high-grade gliomas who had been treated with BNCT. The study population consisted of 87 patients with supratentorial high-grade gliomas; 41 had newly diagnosed tumors and 46 had recurrent tumors. Thirty of 87 patients who were treated between January 2002 and July 2013 developed CSFD. Tumor histology before BNCT and immunohistochemical staining for two molecular markers, Ki-67 and IDH1^R132H, were evaluated for 20 of the 30 patients for whom pathology slides were available. Fluorescence in situ hybridization (FISH) was performed on 3 IDH1^R132H-positive and 1 control IDH1^R132H-negative tumors in order to determine chromosome 1p and 19q status. Histopathologic evaluation revealed that 10 of the 20 patients' tumors were IDH1^R132H-negative small cell GBMs. The remaining patients had tumors consisting of other IDH1^R132H-negative GBM variants, an IDH1^R132H-positive GBM and two anaplastic oligodendrogliomas. Ki-67 immunopositivity ranged from 2 to 75%. In summary, IDH1^R132H-negative GBMs, especially small cell GBMs, accounted for a disproportionately large number of patients who had CSF dissemination. This suggests that these tumor types had an increased propensity to disseminate via the CSF following BNCT and that these patients are at high risk for this clinically serious event.

Sparing of normal tissues with volumetric arc radiation therapy for glioblastoma: single institution clinical experience

Background

Patients with glioblastoma multiforme (GBM) require radiotherapy as part of definitive management. Our institution has adopted the use of volumetric arc therapy (VMAT) due to superior sparing of the adjacent organs at risk (OARs) compared to intensity modulated radiation therapy (IMRT). Here we report our clinical experience by analyzing target coverage and sparing of OARs for 90 clinical treatment plans.

Methods

VMAT and IMRT patient cohorts comprising 45 patients each were included in this study. For all patients, the planning target volume (PTV) received 50 Gy in 30 fractions, and the simultaneous integrated boost PTV received 60 Gy. The characteristics of the two patient cohorts were examined for similarity. The doses to target volumes and OARs, including brain, brainstem, hippocampi, optic nerves, eyes, and cochleae were then compared using statistical analysis. Target coverage and normal tissue sparing for six patients with both clinical IMRT and VMAT plans were analyzed.

Results

PTV coverage of at least 95% was achieved for all plans, and the median mean dose to the boost PTV differed by only 0.1 Gy between the IMRT and VMAT plans. Superior sparing of the brainstem was found with VMAT, with a median difference in mean dose being 9.4 Gy. The ipsilateral cochlear mean dose was lower by 19.7 Gy, and the contralateral cochlea was lower by 9.5 Gy. The total treatment time was reduced by 5 min. The difference in the ipsilateral hippocampal D_100% was 12 Gy, though this is not statistically significant (P = 0.03).

Conclusions

VMAT for GBM patients can provide similar target coverage, superior sparing of the brainstem and cochleae, and be delivered in a shorter period of time compared with IMRT. The shorter treatment time may improve clinical efficiency and the quality of the treatment experience. Based on institutional clinical experience, use of VMAT for the treatment of GBMs appears to offer no inferiority in comparison to IMRT and may offer distinct advantages, especially for patients who may require re-irradiation.

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.

Transtentorial dissemination of optic nerve glioblastoma: case report

Optic nerve glioblastoma is a rare entity that usually presents with rapidly progressive vision loss, which eventually results in blindness and, ultimately, death. As with malignant gliomas in other anatomical locations, local recurrence is common. Isolated rapid changes in vision, atypical neuroimaging findings, and the rarity of optic nerve glioblastoma may render diagnosis challenging and, thus, delay treatment. The authors present a case of optic nerve glioblastoma that was treated with subtotal resection followed by adjuvant radiation therapy and temozolomide. One year following the initial diagnosis, the patient developed a right cerebellar lesion, which was histopathologically consistent with glioblastoma. This case represents the first report of transtentorial dissemination of an optic nerve glioblastoma. In addition, the authors reviewed the literature regarding optic nerve glioblastomas. Of the 73 previously reported cases of malignant optic nerve gliomas, 32 were histologically confirmed glioblastomas. The mean age at diagnosis was 62 years, and 56% were male; the median survival was 7 months. A malignant glioma of the optic nerve should be considered in the differential diagnosis of a patient with rapidly progressive visual loss. However, the incidence of optic nerve glioblastoma is exceedingly low.

The role of radiation in treating glioblastoma: here to stay

Despite numerous efforts over the past several decades, few therapeutic breakthroughs in the treatment of GBM have been realized, and even these have yielded only incrementally modest gains. Radiotherapy remains a crucial component in the management of this disease. In this review, the historical basis for inclusion of radiotherapy as part of the therapeutic regimen for GBM is examined. Additionally, an overview of the evidence supporting the modern role of radiotherapy is provided along with a discussion of standard and emerging combined modality therapies. Finally, GBM management guidelines from three professional societies are reviewed.

A Multiparametric Model for Mapping Cellularity in Glioblastoma Using Radiographically Localized Biopsies

BACKGROUND AND PURPOSE

The complex MR imaging appearance of glioblastoma is a function of underlying histopathologic heterogeneity. A better understanding of these correlations, particularly the influence of infiltrating glioma cells and vasogenic edema on T2 and diffusivity signal in nonenhancing areas, has important implications in the management of these patients. With localized biopsies, the objective of this study was to generate a model capable of predicting cellularity at each voxel within an entire tumor volume as a function of signal intensity, thus providing a means of quantifying tumor infiltration into surrounding brain tissue.

MATERIALS AND METHODS

Ninety-one localized biopsies were obtained from 36 patients with glioblastoma. Signal intensities corresponding to these samples were derived from T1-postcontrast subtraction, T2-FLAIR, and ADC sequences by using an automated coregistration algorithm. Cell density was calculated for each specimen by using an automated cell-counting algorithm. Signal intensity was plotted against cell density for each MR image.

RESULTS

T2-FLAIR (r = -0.61) and ADC (r = -0.63) sequences were inversely correlated with cell density. T1-postcontrast (r = 0.69) subtraction was directly correlated with cell density. Combining these relationships yielded a multiparametric model with improved correlation (r = 0.74), suggesting that each sequence offers different and complementary information.

CONCLUSIONS

Using localized biopsies, we have generated a model that illustrates a quantitative and significant relationship between MR signal and cell density. Projecting this relationship over the entire tumor volume allows mapping of the intratumoral heterogeneity in both the contrast-enhancing tumor core and nonenhancing margins of glioblastoma and may be used to guide extended surgical resection, localized biopsies, and radiation field mapping.

Impact of Including Peritumoral Edema in Radiotherapy Target Volume on Patterns of Failure in Glioblastoma following Temozolomide-based Chemoradiotherapy

We assessed the impact of including peritumoral edema in radiotherapy volumes on recurrence patterns among glioblastoma multiforme (GBM) patients treated with standard chemoradiotherapy (CRT). We analyzed 167 patients with histologically confirmed GBM who received temozolomide (TMZ)-based CRT between May 2006 and November 2012. The study cohort was divided into edema (+) (n = 130) and edema (−) (n = 37) groups, according to whether the entire peritumoral edema was included. At a median follow-up of 20 months (range, 2–99 months), 118 patients (71%) experienced progression/recurrence (infield: 69%; marginal: 26%; outfield: 16%; CSF seeding: 12%). The median overall survival and progression-free survival were 20 months and 15 months, respectively. The marginal failure rate was significantly greater in the edema (−) group (37% vs. 22%, p = 0.050). Among 33 patients who had a favorable prognosis (total resection and MGMT-methylation), the difference in the marginal failure rates was increased (40% vs. 14%, p = 0.138). Meanwhile, treatment of edema did not significantly increase the incidence of pseudoprogression/radiation necrosis (edema (−) 49% vs. (+) 37%, p = 0.253). Inclusion of peritumoral edema in the radiotherapy volume can reduce marginal failures following TMZ-based CRT without increasing pseudoprogression/radiation necrosis.

Upfront boost Gamma Knife “leading-edge” radiosurgery to FLAIR MRI–defined tumor migration pathways in 174 patients with glioblastoma multiforme: a 15-year assessment of a novel therapy

OBJECTIVE

Glioblastoma multiforme (GBM) is composed of cells that migrate through the brain along predictable white matter pathways. Targeting white matter pathways adjacent to, and leading away from, the original contrast-enhancing tumor site (termed leading-edge radiosurgery [LERS]) with single-fraction stereotactic radiosurgery as a boost to standard therapy could limit the spread of glioma cells and improve clinical outcomes.

METHODS

Between December 2000 and May 2016, after an initial diagnosis of GBM and prior to or during standard radiation therapy and carmustine or temozolomide chemotherapy, 174 patients treated with radiosurgery to the leading edge (LE) of tumor cell migration were reviewed. The LE was defined as a region outside the contrast-enhancing tumor nidus, defined by FLAIR MRI. The median age of patients was 59 years (range 22–87 years). Patients underwent LERS a median of 18 days from original diagnosis. The median target volume of 48.5 cm3 (range 2.5–220.0 cm3) of LE tissue was targeted using a median dose of 8 Gy (range 6–14 Gy) at the 50% isodose line.

RESULTS

The median overall survival was 23 months (mean 43 months) from diagnosis. The 2-, 3-, 5-, 7-, and 10-year actual overall survival rates after LERS were 39%, 26%, 16%, 10%, and 4%, respectively. Nine percent of patients developed treatment-related imaging-documented changes due to LERS. Nineteen percent of patients were hospitalized for management of edema, 22% for resection of a tumor cyst or new tumor bulk, and 2% for shunting to treat hydrocephalus throughout the course of their disease. Of the patients still alive, Karnofsky Performance Scale scores remained stable in 90% of patients and decreased by 1–3 grades in 10% due to symptomatic treatment-related imaging changes.

CONCLUSIONS

LERS is a safe and effective upfront adjunctive therapy for patients with newly diagnosed GBM. Limitations of this study include a single-center experience and single-institution determination of the LE tumor target. Use of a leading-edge calculation algorithm will be described to achieve a consistent approach to defining the LE target for general use. A multicenter trial will further elucidate its value in the treatment of GBM.

Aggressive resection at the infiltrative margins of glioblastoma facilitated by intraoperative fluorescein guidance

OBJECTIVE Extent of resection is an important prognostic factor in patients undergoing surgery for glioblastoma (GBM). Recent evidence suggests that intravenously administered fluorescein sodium associates with tumor tissue, facilitating safe maximal resection of GBM. In this study, the authors evaluate the safety and utility of intraoperative fluorescein guidance for the prediction of histopathological alteration both in the contrast-enhancing (CE) regions, where this relationship has been established, and into the non-CE (NCE), diffusely infiltrated margins. METHODS Thirty-two patients received fluorescein sodium (3 mg/kg) intravenously prior to resection. Fluorescence was intraoperatively visualized using a Zeiss Pentero surgical microscope equipped with a YELLOW 560 filter. Stereotactically localized biopsy specimens were acquired from CE and NCE regions based on preoperative MRI in conjunction with neuronavigation. The fluorescence intensity of these specimens was subjectively classified in real time with subsequent quantitative image analysis, histopathological evaluation of localized biopsy specimens, and radiological volumetric assessment of the extent of resection. RESULTS Bright fluorescence was observed in all GBMs and localized to the CE regions and portions of the NCE margins of the tumors, thus serving as a visual guide during resection. Gross-total resection (GTR) was achieved in 84% of the patients with an average resected volume of 95%, and this rate was higher among patients for whom GTR was the surgical goal (GTR achieved in 93.1% of patients, average resected volume of 99.7%). Intraoperative fluorescein staining correlated with histopathological alteration in both CE and NCE regions, with positive predictive values by subjective fluorescence evaluation greater than 96% in NCE regions. CONCLUSIONS Intraoperative administration of fluorescein provides an easily visualized marker for glioma pathology in both CE and NCE regions of GBM. These findings support the use of fluorescein as a microsurgical adjunct for guiding GBM resection to facilitate safe maximal removal.