Treatment of patients with primary glioblastoma multiforme with standard postoperative radiotherapy and radiosurgical boost: prognostic factors and long-term outcome

Stereotactic radiosurgery for glioblastoma considering tumor genetic profiles: an international multicenter study

OBJECTIVE

Molecular profiles, such as isocitrate dehydrogenase (IDH) mutation and O6-methylguanine-DNA methyltransferase (MGMT) methylation status, have important prognostic roles for glioblastoma patients. The authors studied the efficacy and safety of stereotactic radiosurgery (SRS) for glioblastoma patients with consideration of molecular tumor profiles.

METHODS

For this retrospective observational multiinstitutional study, the authors pooled consecutive patients who were treated using SRS for glioblastoma at eight institutions participating in the International Radiosurgery Research Foundation. They evaluated predictors of overall and progression-free survival with consideration of IDH mutation and MGMT methylation status.

RESULTS

Ninety-six patients (median age 56 years) underwent SRS (median dose 15 Gy and median treatment volume 5.53 cm3) at 147 tumor sites (range 1 to 7). The majority of patients underwent prior fractionated radiation therapy (92%) and temozolomide chemotherapy (98%). Most patients were treated at recurrence (85%), and boost SRS was used for 12% of patients. The majority of patients harbored IDH wild-type (82%) and MGMT-methylated (62%) tumors. Molecular data were unavailable for 33 patients. Median survival durations after SRS were similar between patients harboring IDH wild-type tumors and those with IDH mutant tumors (9.0 months vs 11 months, respectively), as well as between those with MGMT-methylated tumors and those with MGMT-unmethylated tumors (9.8 vs. 9.0 months, respectively). Prescription dose > 15 Gy (OR 0.367, 95% CI 0.190-0.709, p = 0.003) and treatment volume > 5 cm3 (OR 1.036, 95% CI 1.007-1.065, p = 0.014) predicted overall survival after controlling for age and IDH status. Treatment volume > 5 cm3 (OR 2.215, 95% CI 1.159-4.234, p = 0.02) and absence of gross-total resection (OR 0.403, 95% CI 0.208-0.781, p = 0.007) were associated with inferior local control of SRS-treated lesions in multivariate models. Nine patients experienced adverse radiation events after SRS, and 7 patients developed radiation necrosis at 59 to 395 days after SRS.

CONCLUSIONS

Post-SRS survival was similar as a function of IDH mutation and MGMT promoter methylation status, suggesting that molecular profiles of glioblastoma should be considered when selecting candidates for SRS. SRS prescription dose > 15 Gy and treatment volume ≤ 5 cm3 were associated with longer survival, independent of age and IDH status. Prior gross-total resection and smaller treatment volume were associated with superior local control.

Peritumoral edema status of glioblastoma identifies patients reaching long-term disease control with specific progression patterns after tumor resection and high-dose proton boost

Background

Glioblastoma peritumoral edema (PE) extent is associated with survival and progression pattern after tumor resection and radiotherapy (RT). To increase tumor control, proton beam was adopted to give high-dose boost (> 90 Gy). However, the correlation between PE extent and prognosis of glioblastoma after postoperative high-dose proton boost (HDPB) therapy stays unknown. We intend to utilize the PE status to classify the survival and progression patterns.

Methods

Patients receiving HDPB (96.6 GyE) were retrospectively evaluated. Limited peritumoral edema (LPE) was defined as PE extent < 3 cm with a ratio of PE extent to tumor maximum diameter of < 0.75. Extended progressive disease (EPD) was defined as progression of tumors extending > 1 cm from the tumor bed edge.

Results

After long-term follow-up (median 88.7, range 63.6–113.8 months) for surviving patients with (n = 13) and without (n = 32) LPE, the median overall survival (OS) and progression-free survival (PFS) were 77.2 vs. 16.7 months (p = 0.004) and 13.6 vs. 8.6 months (p = 0.02), respectively. In multivariate analyses combined with factors of performance, age, tumor maximum diameter, and tumor resection extent, LPE remained a significant factor for favorable OS and PFS. The rates of 5-year complete response, EPD, and distant metastasis with and without LPE were 38.5% vs. 3.2% (p = 0.005), 7.7% vs. 40.6% (p = 0.04), and 0% vs. 34.4% (p = 0.02), respectively.

Conclusions

The LPE status effectively identified patients with relative long-term control and specific progression patterns after postoperative HDPB for glioblastoma.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00432-021-03765-6.

Advances in radiotherapy and comprehensive treatment of high-grade glioma: immunotherapy and tumor-treating fields

High-grade gliomas (HGGs) are the most common primary malignant brain tumors. They have a high degree of malignancy and show invasive growth. The personal treatment plan for HGG is based on the patient's age, performance status, and degree of tumor invasion. The basic treatment plan for HGG involves tumor resection, radiotherapy (RT) with concomitant temozolomide (TMZ), and adjuvant TMZ chemotherapy. The basic radiation technology includes conventional RT, three-dimensional conformal RT, intensity-modulated RT, and stereotactic RT. As our understanding of tumor pathogenesis has deepened, so-called comprehensive treatment schemes have attracted attention. These combine RT with chemotherapy, molecular targeted therapy, immunotherapy, or tumor-treating fields. These emerging treatments are expected to improve the prospects of patients with HGG. In the present article, we review the recent advances in RT and comprehensive treatment for patients with newly diagnosed and recurrent HGG.

Mechanical properties of human glioma

Brain gliomas represent some of the most aggressive tumors encountered by modern medicine and, despite major efforts to optimize early diagnosis and treatment, the prognosis remains poor. Due to the complex structure of the brain and the unique mechanical properties of the extracellular matrix, gliomas invade and expand into the brain parenchyma, along white matter tracts and within perivascular spaces, usually sparing normal vessels. Different methods have been developed to study the mechanical properties of gliomas in a wide range of scales, from cells and the microscale to tissues and the macroscale. In this review, the current view on glioma mechanics is presented and the methods used to determine glioma mechanical properties are outlined. Their principles and current state of affairs are discussed.

Guiding Treatment Choices for Elderly Patients with Glioblastoma by a Comprehensive Geriatric Assessment

PURPOSE OF REVIEW

The incidence of glioblastoma multiforme (GBM) increases with age; more than half of newly diagnosed patients are older than 65 years. Due to age-dependent decreasing organ functions, comorbidities, functional decline, and increasing risk of social isolation, not all patients are able to tolerate standard therapy of GBM with 6 weeks of radiochemotherapy.

RECENT FINDINGS

A set of alleviated therapies, e.g., chemotherapy or radiotherapy alone, hypofractionated radiotherapies with different total doses and variable fractionation regimens as well as hypofractionated radiotherapy with concomitant and adjuvant chemotherapy, have been evaluated during the last years. However, clinicians are still unsure which therapy would fit best to a given patient. Recently, the predictive value of comprehensive geriatric assessment regarding tolerance of chemotherapy and prediction of early mortality has been validated for older GBM patients in a retrospective trial. Thus, it appears that neuro-oncology is now ready for the prospective implementation of geriatric assessment to guide treatment planning for elderly GBM patients.

Survival after hypofractionation in glioblastoma: a systematic review and meta-analysis

BACKGROUND

Glioblastoma multiforme (GBM) has a poor prognosis despite a multi modal treatment that includes normofractionated radiotherapy. So, various hypofractionated alternatives to normofractionated RT have been tested to improve such prognosis. There is need of systematic review and meta-analysis to analyse the literature properly and maybe generalised the use of hypofractionation. The aim of this study was first, to perform a meta-analysis of all controlled trials testing the impact of hypofractionation on survival without age restriction and secondly, to analyse data from all non-comparative trials testing the impact of hypofractionation, radiosurgery and hypofractionated stereotactic RT in first line.

MATERIALS/METHODS

We searched Medline, Embase and Cochrane databases to identify all publications testing the impact of hypofractionation in glioblastoma between 1985 and March 2020. Combined hazard ratio from comparative studies was calculated for overall survival. The impact of study design, age and use of adjuvant temozolomide was explored by stratification. Meta-regressions were performed to determine the impact of prognostic factors.

RESULTS

2283 publications were identified. Eleven comparative trials were included. No impact on overall survival was evidenced (HR: 1.07, 95%CI: 0.89-1.28) without age restriction. The analysis of non-comparative literature revealed heterogeneous outcomes with limited quality of reporting. Concurrent chemotherapy, completion of surgery, immobilization device, isodose of prescription, and prescribed dose (depending on tumour volume) were poorly described. However, results on survival are encouraging and were correlated with the percentage of resected patients and with patients age but not with median dose.

CONCLUSIONS

Because few trials were randomized and because the limited quality of reporting, it is difficult to define the place of hypofactionation in glioblastoma. In first line, hypofractionation resulted in comparable survival outcome with the benefit of a shortened duration. The method used to assess hypofractionation needs to be improved.

Study Protocol: Early Stereotactic Gamma Knife Radiosurgery to Residual Tumor After Surgery of Newly Diagnosed Glioblastoma (Gamma-GBM)

BACKGROUND

Glioblastoma (GBM) is the most common malignant brain tumor in adult patients. Tumor recurrence commonly occurs around the resection cavity, especially after subtotal resection (STR). Consequently, the extent of resection correlates with overall survival (OS), suggesting that depletion of postoperative tumor remnants will improve outcome.

OBJECTIVE

To assess safety and efficacy of adding stereotactic radiosurgery (SRS) to the standard treatment of GBM in patients with postoperative residual tumor.

METHODS

Gamma-GBM is a single center, open-label, prospective, single arm, phase II study that includes patients with newly diagnosed GBM (intraoperative via frozen sections) who underwent STR (residual tumor will be identified by native and contrast enhanced T1-weighted magnetic resonance imaging scans). All patients will receive SRS with 15 Gy (prescribed to the 50% isodose enclosing all areas of residual tumor) early (within 24-72 h) after surgery. Thereafter, all patients undergo standard-of-care therapy for GBM (radiochemotherapy with 60 Gy external beam radiotherapy [EBRT] plus concomitant temozolomide and 6 cycles of adjuvant temozolomide chemotherapy). The primary outcome is median progression-free survival, secondary outcomes are median OS, occurrence of radiation induced acute (<3 wk), early delayed (<3 mo), and late (>3 mo post-SRS) neurotoxicity and incidence of symptomatic radionecrosis.

EXPECTED OUTCOMES

We expect to detect efficacy and safety signals by the immediate application of SRS to standard-of-care therapy in newly diagnosed GBM.

DISCUSSION

Early postoperative SRS to areas of residual tumor could bridge the therapeutic gap between surgery and adjuvant therapies.

Value of the visual and semiquantitative analysis of carbon-11-methionine PET/CT in brain tumors' recurrence versus post-therapeutic changes

To compare the visual and semiquantitative analysis of carbon-11-methionine (C-MET) PET/computed tomography (CT) images in patients with primary brain tumors and suspected recurrence, persistence, or necrotic post-therapeutic changes. A total of 41 consecutive C-MET-PET/CT scans on 35 (21 men, mean age 44.1±16.6 years) patients were requested for MRI suspicion of recurrent or persistent primary tumor after therapy. The C-MET PET/CT were obtained 20 min after an intravenous injection of 555-740 MBq (15-20 mCi) of C-MET. Both visual and semiquantitative evaluations were performed comparing C-MET uptake between suspicious areas and different lesion/normal-to-background ratios. The final diagnosis was established by histological examination in 12 cases and clinical and MRI follow-up in 29 cases. Visual analyses were positive in 27 (63.4%) and negative in 14 (36.6%) of the C-MET PET/CT. The sensitivity was 83.9%, specificity was 90.0%, positive predictive value was 96.3%, negative predictive value was 64.3% and accuracy was 71.4%. For the semiquantitative analysis, all the lesion/normal-to-background ratios could differentiate between tumor and nontumor (P<0.001), the lesion/contralateral parenchyma (L/CP) maximum standardized uptake value (SUVmax) being the index with the highest area under de curve (0.938). Applying an L/CP SUVmax index of 1.21, the sensitivity was 89.3%, specificity was 90.0%, positive predictive value was 96.1%, negative predictive value was 75%, and accuracy was 82.9%. C-MET-PET/CT was a useful technique to differentiate post-therapeutic changes from tumor presence in treated patients with brain neoplasm in whom cerebral MRI is nonconclusive, showing a high diagnostic performance. Our results showed only slight differences between visual analysis methods and the L/CP SUVmax ratio, the best of the semiquantitative methods.

Survival and complications of stereotactic radiosurgery: A systematic review of stereotactic radiosurgery for newly diagnosed and recurrent high-grade gliomas

BACKGROUND

Utilization of stereotactic radiosurgery (SRS) for treatment of high-grade gliomas (HGGs) has been slowly increasing with variable reported success rates.

OBJECTIVE

Systematic review of the available data to evaluate the efficacy of SRS as a treatment for HGG with regards to median overall survival (OS) and progression-free survival (PFS), in addition to ascertaining the rate of radiation necrosis and other SRS-related major neurological complications.

METHODS

Literature searches were performed for publications from 1992 to 2016. The pooled estimates of median PFS and median OS were calculated as a weighted estimate of population medians. Meta-analyses of published rates of radiation necrosis and other major neurological complications were also performed.

RESULTS

Twenty-nine studies reported the use of SRS for recurrent HGG, and 16 studies reported the use of SRS for newly diagnosed HGG. For recurrent HGG, the pooled estimates of median PFS and median OS were 5.42 months (3-16 months) and 20.19 months (9-65 months), respectively; the pooled radiation necrosis rate was 5.9% (0-44%); and the pooled estimates of major neurological complications rate was 3.3% (0-23%). For newly diagnosed HGG, the pooled estimates of median PFS and median OS were 7.89 months (5.5-11 months) and 16.87 months (9.5-33 months) respectively; the pooled radiation necrosis rate was 6.5% (0-33%); and the pooled estimates of other major neurological complications rate was 1.5% (0-25%).

CONCLUSION

Our results suggest that SRS holds promise as a relatively safe treatment option for HGG. In terms of efficacy at this time, there are inadequate data to support routine utilization of SRS as the standard of care for newly diagnosed or recurrent HGG. Further studies should be pursued to define more clearly the therapeutic role of SRS.

The radiosurgery fractionation quandary: single fraction or hypofractionation?

Stereotactic radiosurgery (SRS), typically administered in a single session, is widely employed to safely, efficiently, and effectively treat small intracranial lesions. However, for large lesions or those in close proximity to critical structures, it can be difficult to obtain an acceptable balance of tumor control while avoiding damage to normal tissue when single-fraction SRS is utilized. Treating a lesion in 2 to 5 fractions of SRS (termed "hypofractionated SRS" [HF-SRS]) potentially provides the ability to treat a lesion with a total dose of radiation that provides both adequate tumor control and acceptable toxicity. Indeed, studies of HF-SRS in large brain metastases, vestibular schwannomas, meningiomas, and gliomas suggest that a superior balance of tumor control and toxicity is observed compared with single-fraction SRS. Nonetheless, a great deal of effort remains to understand radiobiologic mechanisms for HF-SRS driving the dose-volume response relationship for tumors and normal tissues and to utilize this fundamental knowledge and the results of clinic studies to optimize HF-SRS. In particular, the application of HF-SRS in the setting of immunomodulatory cancer therapies offers special challenges and opportunities.

Principles of radiation therapy

Although resection remains the mainstay in the treatment of gliomas, microscopically complete resection of most central nervous system tumors remains challenging, and is, in fact, rarely accomplished. Considering their invasive nature, gross total resections to clearly negative margins often do or would require removal or transection of functional brain, with likely serious neurologic deficits. Consequently, radiotherapy has emerged as an indispensable component of therapy. It is delivered primarily by external-beam radiotherapy or brachytherapy techniques. Herein, we present the biologic principles, techniques, and applications of radiotherapy in glioma treatment today.

Stereotactic Radiosurgery for Glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and one of the most aggressive of all human cancers. GBM tumors are highly infiltrative and relatively resistant to conventional therapies. Aggressive management of GBM using a combination of surgical resection, followed by fractionated radiotherapy and chemotherapy has been shown to improve overall survival; however, GBM tumors recur in the majority of patients and the disease is most often fatal. There is a need to develop new treatment regimens and technological innovations to improve the overall survival of GBM patients. The role of stereotactic radiosurgery (SRS) for the treatment of GBM has been explored and is controversial. SRS utilizes highly precise radiation techniques to allow dose escalation and delivery of ablative radiation doses to the tumor while minimizing dose to the adjacent normal structures. In some studies, SRS with concurrent chemotherapy has shown improved local control with acceptable toxicities in select GBM patients. However, because GBM is a highly infiltrative disease, skeptics argue that local therapies, such as SRS, do not improve overall survival. The purpose of this article is to review the literature regarding SRS in both newly diagnosed and recurrent GBM, to describe SRS techniques, potential eligible SRS candidates, and treatment-related toxicities. In addition, this article will propose promising areas for future research for SRS in the treatment of GBM.

Evaluation of pre-radiotherapy apparent diffusion coefficient (ADC): patterns of recurrence and survival outcomes analysis in patients treated for glioblastoma multiforme

PURPOSE

To investigate the association of pre-radiotherapy apparent diffusion coefficient (ADC) abnormalities with patterns of recurrence and outcomes in patients with glioblastoma multiforme (GBM).

MATERIALS AND METHODS

Fifty-two patients with recurrent GBM were retrospectively evaluated. Diffusion MRI images were acquired for all patients postoperatively prior to radiotherapy. ADC images were evaluated for geographic regions of diffusion restriction (hypointensity) within the FLAIR volume. If identified, the ADC map and the T1+C MRI at the time of recurrence were registered to the original plan to determine the pattern of recurrence and the coverage of the ADC abnormality by the 60 Gy isodose line (IDL). Progression-free and overall survival was determined for patients with and without an ADC hypointensity.

RESULTS

An ADC hypointensity was identified in 32 (62%) of cases. The recurrence pattern in these cases was central in 27/32 (84%), marginal in 4/32 (13%) and distant in 1/32 (3%). The recurrence overlapped with the ADC hypointensity in 28 (88%) patients. The ADC hypointensity was covered by 95% of the 60 Gy IDL in all cases. Kaplan-Meier analysis revealed inferior progression free survival and overall survival in patients with an ADC hypointensity compared to those without, despite similarities between the groups in terms of age, RT dose, performance status, and extent of resection.

CONCLUSIONS

The presence of an ADC hypointensity on pre-radiotherapy diffusion-weighted imaging is associated with the location of tumor recurrence as demonstrated by frequent overlap in this series, and is associated with a trend toward inferior outcomes. This abnormality may reflect a high risk region of hypercellularity and warrants consideration with respect to radiotherapy planning.

Role of adjuvant or salvage radiosurgery in the management of unresected residual or progressive glioblastoma multiforme in the pre-bevacizumab era

OBJECT

After initial standard of care management of glioblastoma multiforme (GBM), relatively few proven options remain for patients with unresected progressive tumor. Numerous reports describe the value of radiosurgery, yet this modality appears to remain underutilized. The authors analyzed the outcomes of early adjuvant stereotactic radiosurgery (SRS) for unresected tumor or later salvage SRS for progressive GBM. Radiosurgery was performed as part of the multimodality management and was combined with other therapies. Patients continued to receive additional chemotherapy after SRS and prior to progression being documented. In this retrospective analysis, the authors evaluated factors that affected patient overall survival (OS) and progression-free survival.

METHODS

Between 1987 and 2008 the authors performed Gamma Knife SRS in 297 patients with histologically proven GBMs. All patients had received prior fractionated radiation therapy, and 66% had undergone one or more chemotherapy regimens. Ninety-six patients with deep-seated unresectable GBMs underwent biopsy only. Of those in whom excision had been possible, resection was considered to be gross total in 68 and subtotal in 133. The median patient age was 58 years (range 23-89 years) and the median tumor volume was 14 cm(3) (range 0.26-84.2 cm(3)). The median prescription dose delivered to the imaging-defined tumor margin was 15 Gy (range 9-25 Gy). The median follow-up duration was 8.6 months (range 1.1-173 months). Cox regression models were used to analyze survival outcomes. Variables examined included age, residual versus recurrent tumor, prior chemotherapy, time to first recurrence, SRS dose, and gross tumor volume.

RESULTS

The median survival times after radiosurgery and after diagnosis were 9.03 and 18.1 months, respectively. The 1-year and 2-year OS after SRS were 37.9% and 16.7%, respectively. The 1-year and 2-year OS after diagnosis were 76.2% and 30.8%, respectively. Using multivariate analysis, factors associated with improved OS after diagnosis were younger age (< 60 years) at diagnosis (p < 0.0001), tumor volume < 14 cm(3) (p < 0.001), use of prior chemotherapy (p = 0.001), and radiosurgery at the time of recurrence (p < 0.0001). Multivariate analysis showed that younger age (p < 0.0001) and smaller tumor volume (< 14 cm(3)) (p = 0.001) were significantly associated with increased OS after SRS. Adverse radiation effects were seen in 69 patients (23%). Fifty-eight patients (19.5%) underwent additional resection after SRS. The median survivals after diagnosis for recursive partitioning analysis Classes III, IV and V+VI were 31.6, 20.8, and 16.7 months, respectively.

CONCLUSIONS

In this analysis 30% of a heterogeneous cohort of GBM patients eligible for SRS had an OS of 2 years. Radiosurgery at the time of tumor progression was associated with a median survival of 21.8 months. The role of radiosurgery for GBMs remains controversial. The findings in this study support the need for a funded and appropriately designed clinical trial that will provide a higher level of evidence regarding the future role of SRS for glioblastoma patients in whom disease has progressed despite standard management.

siRNA targeting stathmin inhibits invasion and enhances chemotherapy sensitivity of stem cells derived from glioma cell lines

Glioma is one of the most highly angiogenic tumors, and glioma stem cells (GSCs) are responsible for resistance to chemotherapy and radiotherapy, as well as recurrence after operation. Stathmin is substantial for mitosis and plays an important role in proliferation and migration of glioma-derived endothelial cells. However, the relationship between stathmin and GSCs is incompletely understood. Here we isolated GSCs from glioma cell lines U87MG and U251, and then used siRNA targeting stathmin for silencing. We showed that silencing of stathmin suppressed the proliferation, increased the apoptosis rate, and arrested the cell cycle at G2/M phase in GSCs. Silencing of stathmin in GSCs also resulted in inhibited the migration/invasion as well as the capability of vasculogenic mimicry. The susceptibility of GSCs to temozolomide was also enhanced by stathmin silencing. Our findings suggest stathmin as a potential target in GSCs for glioma treatment.

Glioblastoma recurrence patterns after radiation therapy with regard to the subventricular zone

PURPOSE

We evaluated the influence of tumor location and tumor spread in primary glioblastoma (GBM), with respect to the subventricular zone (SVZ), on recurrence behavior, progression-free survival (PFS), and overall survival (OS).

METHODS AND MATERIALS

607 patients (376 male and 231 female) with a median age of 61.3 years (range, 3.0-87.9 years) and primary GBM treated with radiation therapy (RT) from 2004 to 2012 at a single institution were included in this retrospective study. Preoperative images and follow-up examination results were assessed to evaluate tumor location. Tumors were classified according to the tumor location in relation to the SVZ.

RESULTS

The median PFS of the study population was 5.2 months (range, 1-91 months), and the median OS was 13.8 months (range, 1-102 months). Kaplan-Meier analysis showed that tumor location in close proximity to the SVZ was associated with a significant decline in PFS and OS (4.8 and 12.3 months, respectively; each P<.001). Furthermore, in cases where tumors were involved with the SVZ, distant cerebral progression (43.8%; P=.005) and multifocal progression (39.8%; P=.008) were more common. Interestingly, opening of the ventricle during the previous surgery showed no impact on PFS and OS.

CONCLUSION

GBM in close proximity to the SVZ was associated with decreased survival and had a higher risk of multifocal or distant progression. Ventricle opening during surgery had no effect on survival rates.

Sequential administration of carbon nanotubes and near-infrared radiation for the treatment of gliomas

The objective was to use carbon nanotubes (CNT) coupled with near-infrared radiation (NIR) to induce hyperthermia as a novel non-ionizing radiation treatment for primary brain tumors, glioblastoma multiforme (GBM). In this study, we report the therapeutic potential of hyperthermia-induced thermal ablation using the sequential administration of carbon nanotubes (CNT) and NIR. In vitro studies were performed using glioma tumor cell lines (U251, U87, LN229, T98G). Glioma cells were incubated with CNTs for 24 h followed by exposure to NIR for 10 min. Glioma cells preferentially internalized CNTs, which upon NIR exposure, generated heat, causing necrotic cell death. There were minimal effects to normal cells, which correlate to their minimal uptake of CNTs. Furthermore, this protocol caused cell death to glioma cancer stem cells, and drug-resistant as well as drug-sensitive glioma cells. This sequential hyperthermia therapy was effective in vivo in the rodent tumor model resulting in tumor shrinkage and no recurrence after only one treatment. In conclusion, this sequence of selective CNT administration followed by NIR activation provides a new approach to the treatment of glioma, particularly drug-resistant gliomas.

The role of cytoreductive surgery in the management of progressive glioblastoma : a systematic review and evidence-based clinical practice guideline

QUESTION

Should patients with previously diagnosed malignant glioma who are suspected of experiencing progression of the neoplasm process undergo repeat open surgical resection?

TARGET POPULATION

These recommendations apply to adults with previously diagnosed malignant glioma who are suspected of experiencing progression of the neoplastic process and are amenable to surgical resection.

RECOMMENDATIONS LEVEL II

Repeat cytoreductive surgery is recommended in symptomatic patients with locally recurrent or progressive malignant glioma. The median survival in these patient diagnosed with glioblastoma is expected to range from 6 to 17 months following a second procedure. It is recommended that the following preoperative factors be considered when evaluating a patient for repeat operation: location of recurrence in eloquent/critical brain regions, Karnofsky Performance Status and tumor volume.

Malignant gliomas: current perspectives in diagnosis, treatment, and early response assessment using advanced quantitative imaging methods

Malignant gliomas consist of glioblastomas, anaplastic astrocytomas, anaplastic oligodendrogliomas and anaplastic oligoastrocytomas, and some less common tumors such as anaplastic ependymomas and anaplastic gangliogliomas. Malignant gliomas have high morbidity and mortality. Even with optimal treatment, median survival is only 12–15 months for glioblastomas and 2–5 years for anaplastic gliomas. However, recent advances in imaging and quantitative analysis of image data have led to earlier diagnosis of tumors and tumor response to therapy, providing oncologists with a greater time window for therapy management. In addition, improved understanding of tumor biology, genetics, and resistance mechanisms has enhanced surgical techniques, chemotherapy methods, and radiotherapy administration. After proper diagnosis and institution of appropriate therapy, there is now a vital need for quantitative methods that can sensitively detect malignant glioma response to therapy at early follow-up times, when changes in management of nonresponders can have its greatest effect. Currently, response is largely evaluated by measuring magnetic resonance contrast and size change, but this approach does not take into account the key biologic steps that precede tumor size reduction. Molecular imaging is ideally suited to measuring early response by quantifying cellular metabolism, proliferation, and apoptosis, activities altered early in treatment. We expect that successful integration of quantitative imaging biomarker assessment into the early phase of clinical trials could provide a novel approach for testing new therapies, and importantly, for facilitating patient management, sparing patients from weeks or months of toxicity and ineffective treatment. This review will present an overview of epidemiology, molecular pathogenesis and current advances in diagnoses, and management of malignant gliomas.

Inhibition of glioma growth by minocycline is mediated through endoplasmic reticulum stress-induced apoptosis and autophagic cell death

BACKGROUND

We have reported that minocycline (Mino) induced autophagic death in glioma cells. In the present study, we characterize the upstream regulators that control autophagy and switch cell death from autophagic to apoptotic.

METHODS

Western blotting and immunofluorescence were used to detect the expressions of eukaryotic translation initiation factor 2α (eIF2α), transcription factor GADD153 (CHOP), and glucose-regulated protein 78 (GRP78). Short hairpin (sh)RNA was used to knock down eIF2α or CHOP expression. Autophagy was assessed by the conversion of light chain (LC)3-I to LC3-II and green fluorescent protein puncta formation. An intracranial mouse model and bioluminescent imaging were used to assess the effect of Mino on tumor growth and survival time of mice.

RESULTS

The expression of GRP78 in glioma was high, whereas in normal glia it was low. Mino treatment increased GRP78 expression and reduced binding of GRP78 with protein kinase-like endoplasmic reticulum kinase. Subsequently, Mino increased eIF2α phosphorylation and CHOP expression. Knockdown of eIF2α or CHOP reduced Mino-induced LC3-II conversion and glioma cell death. When autophagy was inhibited, Mino induced cell death in a caspase-dependent manner. Rapamycin in combination with Mino produced synergistic effects on LC3 conversion, reduction of the Akt/mTOR/p70S6K pathway, and glioma cell death. Bioluminescent imaging showed that Mino inhibited the growth of glioma and prolonged survival time and that these effects were blocked by shCHOP.

CONCLUSIONS

Mino induced autophagy by eliciting endoplasmic reticulum stress response and switched cell death from autophagy to apoptosis when autophagy was blocked. These results coupled with clinical availability and a safe track record make Mino a promising agent for the treatment of malignant gliomas.

Efficacy and limitations of stereotactic radiosurgery in the treatment of glioblastoma

Treatment of recurrent glioblastoma is still challenging. Stereotactic radiosurgery has been accepted as a treatment option for recurrent glioblastoma after standard chemotherapy and irradiation. However, the efficacy of stereotactic radiosurgery at recurrence has been limited, mainly due to the highly infiltrative nature of the tumor which makes the lesion difficult to define as the target. To enhance the efficacy of stereotactic radiosurgery, several methods of targeting based on neuroimaging technology such as positron emission tomography and magnetic resonance imaging have been adopted to irradiate as many of the viable tumor cells as possible and showed some enhanced efficacy. In a trial of intensified treatment by extending the irradiation field, improvement of local control did not result in longer survival. Radiation-induced adverse event is another problem after stereotactic radiosurgery for recurrent glioblastoma because almost all patients underwent irradiation as a part of the initial treatment. To overcome the side effects associated with re-irradiation, use of bevacizumab, a humanized monoclonal antibody to vascular endothelial growth factor, has shown some efficacy. Advances in irradiation technology, neuroimaging, and adjuvant treatment are needed to enhance the efficacy of stereotactic radiosurgery for recurrent glioblastoma and reduce the morbidity associated with irradiation.

Sulindac sulfide inhibits sarcoendoplasmic reticulum Ca2+ ATPase, induces endoplasmic reticulum stress response, and exerts toxicity in glioma cells: relevant similarities to and important differences from celecoxib

Malignant gliomas have low survival expectations regardless of current treatments. Nonsteroidal anti-inflammatory drugs (NSAIDs) prevent cell transformation and slow cancer cell growth by mechanisms independent of cyclooxygenase (COX) inhibition. Certain NSAIDs trigger the endoplasmic reticulum stress response (ERSR), as revealed by upregulation of molecular chaperones such as GRP78 and C/EBP homologous protein (CHOP). Although celecoxib (CELE) inhibits the sarcoendoplasmic reticulum Ca(2+) ATPase (SERCA), an effect known to induce ERSR, sulindac sulfide (SS) has not been reported to affect SERCA. Here, we investigated these two drugs for their effects on Ca(2+) homeostasis, ERSR, and glioma cell survival. Our findings indicate that SS is a reversible inhibitor of SERCA and that both SS and CELE bind SERCA at its cyclopiazonic acid binding site. Furthermore, CELE releases additional Ca(2+) from the mitochondria. In glioma cells, both NSAIDS upregulate GRP78 and activate ER-associated caspase-4 and caspase-3. Although only CELE upregulates the expression of CHOP, it appears that CHOP induction could be associated with mitochondrial poisoning. In addition, CHOP induction appears to be uncorrelated with the gliotoxicity of these NSAIDS in our experiments. Our data suggest that activation of ERSR is primarily responsible for the gliotoxic effect of these NSAIDS. Because SS has good brain bioavailability, has lower COX-2 inhibition, and has no mitochondrial effects, it represents a more appealing molecular candidate than CELE to achieve gliotoxicity via activation of ERSR.

Treatment outcome and prognostic factors of adult glioblastoma multiforme

INTRODUCTION

This study aimed to report the characteristics, prognostic factors and treatment outcome of 223 patients with glioblastoma multiforme (GBM).

SUBJECTS AND METHOD

This retrospective study was carried out by reviewing the medical records of 223 adult patients diagnosed at a tertiary academic hospital between 1990 and 2008. Patients' follow up ranged from 1 to 69 months (median 11 months). Surgery was attempted in all patients in whom complete resection in 15 patients (7%), subtotal resection in 77 patients (34%), partial resection in 73 patients (33%) and biopsy alone in 58 patients (26%) were done. In addition, we performed a literature review of PubMed to find out and analyze major related series. In all, we collected and analyzed the data of 33 major series including more than 11,000 patients with GBM.

RESULTS

There were 141 men and 82 women. The median progression free- and overall survival were 6 (95% CI=5.711-8.289) and 11 (95% CI=9.304-12.696) months respectively. In univariate analysis for overall survival, age (P=0.003), tumor size (P<0.013), performance status (P<0.001), the extent of surgical resection (P=0.009), dose of radiation (P<0.001), and adjuvant chemotherapy (P<0.001) were prognostic factors. However, in multivariate analysis, only radiation dose, extent of surgical resection, and adjuvant chemotherapy were independent prognostic factors for overall survival.

CONCLUSION

The prognosis of adult patients with GBM remains poor; however, complete surgical resection and adjuvant treatments improve progression-free and overall survival.

Hypofractionated Radiotherapy and Stereotactic Boost with Concurrent and Adjuvant Temozolamide for Glioblastoma in Good Performance Status Elderly Patients - Early Results of a Phase II Trial

Glioblastoma Multiforme (GBM) is an aggressive primary brain neoplasm with dismal prognosis. Based on successful phase III trials, 60 Gy involved-field radiotherapy in 30 fractions over 6 weeks [Standard radiation therapy (RT)] with concurrent and adjuvant temozolomide is currently the standard of care. In this disease, age and Karnofsky Performance Status (KPS) are the most important prognostic factors. For elderly patients, clinical trials comparing standard RT with radiotherapy abbreviated to 40 Gy in 15 fractions over 3 weeks demonstrated similar outcomes, indicating shortened radiotherapy may be an appropriate option for elderly patients. However, these trials did not include temozolomide chemotherapy, and included patients with poor KPS, possibly obscuring benefits of more aggressive treatment for some elderly patients. We conducted a prospective Phase II trial to examine the efficacy of a hypofractionated radiation course followed by a stereotactic boost with concurrent and adjuvant temozolomide chemotherapy in elderly patients with good performance status. In this study, patients 65 years and older with a KPS > 70 and histologically confirmed GBM received 40 Gy in 15 fractions with 3D conformal technique followed by a 1–3 fraction stereotactic boost to the enhancing tumor. All patients also received concurrent and adjuvant temozolomide. Patients were evaluated 1 month post-treatment and every 2 months thereafter. Between 2007 and 2010, 20 patients (9 males and 11 females) were enrolled in this study. The median age was 75.4 years (range 65–87 years). At a median follow-up of 11 months (range 7–32 months), 12 patients progressed and 5 are alive. The median progression free survival was 11 months and the median overall survival was 13 months. There was no additional toxicity. These results indicate that elderly patients with good KPS can achieve outcomes comparable to the current standard of care using an abbreviated radiotherapy course, radiosurgery boost, and temozolomide.

Radiosurgery for high-grade glioma

Background:

For patients with newly diagnosed high-grade gliomas (HGG), the current standard-of-care treatment involves surgical resection, followed by concomitant temozolomide (TMZ) and external beam radiation therapy (XRT), and subsequent TMZ chemotherapy. For patients with recurrent HGG, there is no standard of care. Stereotactic radiosurgery (SRS) is used to deliver focused, relatively large doses of radiation to a small, precisely defined target. Treatment is usually delivered in a single fraction, but may be delivered in up to five fractions. The role of SRS in the management of patients with HGG is not well established.

Methods:

The PubMed database was searched with combinations of relevant MESH headings and limits. Case reports and/or small case series were excluded. Attention was focused on overall median survival as an objective measure, and data were examined separately for newly diagnosed and recurrent HGG.

Results:

With respect to newly diagnosed HGG, there is strong evidence that addition of an SRS boost prior to standard XRT provides no survival benefit. However, recent retrospective evidence suggests a possible survival benefit when SRS is performed after XRT. With respect to recurrent HGG, there is suggestion that SRS may confer a survival benefit but with potentially higher complication rates. Newer studies are investigating the combination of SRS with targeted molecular agents. Controlled prospective clinical trials using advanced imaging techniques are necessary for a complete assessment.

Conclusions:

SRS has the potential to provide a survival benefit for patients with HGG. Further research is clearly warranted to define its role in the management of newly diagnosed and recurrent HGG.

Drug-resistance gene expression and progression of astrocytic tumors

To clarify the influence of biochemotherapy on the progression of astrocytic tumors, the expression of O6-methylguanine DNA-methyltransferase (MGMT) mRNA, as well as of other drug-resistance- and drug-sensitivity-related genes such as multidrug resistance gene 1, multidrug resistance-associated protein, glutathione S-transferase-pi, DNA topoisomerase II, and interferon receptor mRNA, and the interferon regulatory factor (IRF)-1 and -2 ratios in gliomas were investigated by quantitative reverse transcription-polymerase chain reaction (RT-PCR). The mean MGMT/beta2-microglobulin (beta2-MG) ratio for 130 neuroepithelial tumors was 8.2 +/- 17.8. The mean ratio of 45 glioblastomas was significantly higher than that for the other 85 tumors. In contrast, the mean of 26 low-grade gliomas was significantly lower than that of other tumors. The mean IRF-1/IRF-2 ratio of 16 other brain tumors that mainly consisted of medulloblastomas was significantly greater than that of the other 114 tumors. Almost no significant differences were observed between primary and recurrent tumors in the expression of any gene, and before and after therapy with corresponding drugs. The mean MGMT/beta2-MG ratio in primary glioblastomas was significantly higher than that in secondary tumors. These findings suggest that native drug resistance is more important than acquired resistance when glioma therapy is considered.

Integrated boost IMRT with FET-PET-adapted local dose escalation in glioblastomas. Results of a prospective phase II study

PURPOSE

Dose escalations above 60 Gy based on MRI have not led to prognostic benefits in glioblastoma patients yet. With positron emission tomography (PET) using [(18)F]fluorethyl-L-tyrosine (FET), tumor coverage can be optimized with the option of regional dose escalation in the area of viable tumor tissue.

METHODS AND MATERIALS

In a prospective phase II study (January 2008 to December 2009), 22 patients (median age 55 years) received radiochemotherapy after surgery. The radiotherapy was performed as an MRI and FET-PET-based integrated-boost intensity-modulated radiotherapy (IMRT). The prescribed dose was 72 and 60 Gy (single dose 2.4 and 2.0 Gy, respectively) for the FET-PET- and MR-based PTV-FET((72 Gy)) and PTV-MR((60 Gy)). FET-PET and MRI were performed routinely for follow-up. Quality of life and cognitive aspects were recorded by the EORTC-QLQ-C30/QLQ Brain20 and Mini-Mental Status Examination (MMSE), while the therapy-related toxicity was recorded using the CTC3.0 and RTOG scores.

RESULTS

Median overall survival (OS) and disease-free survival (DFS) were 14.8 and 7.8 months, respectively. All local relapses were detected at least partly within the 95% dose volume of PTV-MR((60 Gy)). No relevant radiotherapy-related side effects were observed (excepted alopecia). In 2 patients, a pseudoprogression was observed in the MRI. Tumor progression could be excluded by FET-PET and was confirmed in further MRI and FET-PET imaging. No significant changes were observed in MMSE scores and in the EORTC QLQ-C30/QLQ-Brain20 questionnaires.

CONCLUSION

Our dose escalation concept with a total dose of 72 Gy, based on FET-PET, did not lead to a survival benefit. Acute and late toxicity were not increased, compared with historical controls and published dose-escalation studies.

The role of adjuvant radiation therapy in the management of high-grade gliomas

The purpose of this article is to update the neurosurgical community on the role of adjuvant radiation therapy in the management of patients with high-grade glioma. This information guides clinicians in the multidisciplinary management of these patients via a review of the literature describing current treatment paradigms as well as new avenues of investigation.

Extended field stereotactic radiosurgery for recurrent glioblastoma

BACKGROUND

Stereotactic radiosurgery (SRS) is among the few therapeutic options for glioblastoma that recurs after standard radiation and chemotherapy, but its efficacy has been limited.

METHODS

Since November 2007, the authors have modified the clinical target volume by adding a 0.5- to 1-cm margin to the gadolinium-enhanced area (extended field SRS), in contrast to conventional SRS using no margin to set the clinical target volume. A total of 35 recurred glioblastoma lesions in 9 patients were treated with conventional SRS between December 1990 and January 2007, and 14 lesions in 9 patients were treated with extended field SRS.

RESULTS

The median follow-up periods were 7 months (range, 3-29 months) and 8 months (range, 6-27 months), respectively. The local control rate was 47% for conventional SRS and 93% for extended field SRS (P = .0035), and the numbers of radiation necrosis observed in SRS-treated lesions were 2 and 4, respectively. The median overall survival from the diagnosis was 24 months (range, 14-57 months) for conventional SRS and 21 months (range, 15-51 months) for extended field SRS (statistically not significant). Seven patients treated with conventional SRS died during follow-up, 6 from progression of the SRS-treated tumor, whereas 7 patients treated with extended field SRS died during follow-up, 6 from remote intracerebral dissemination.

CONCLUSIONS

Extended field SRS was superior to conventional SRS in the local control of small recurrent lesions of glioblastoma, although a further device to suppress remote dissemination may be necessary to increase survival.

Clinical significance of vasculogenic mimicry in human gliomas

Vasculogenic mimicry (VM) is known as non-endothelial tumor cell-lined microvascular channels in aggressive tumors. We have previously found the presence of VM in high-grade gliomas. In this study, we aimed to identify VM patterns in gliomas and to explore their clinical significance. Tumor samples as well as their detailed clinical/prognostic data were collected from 101 patients. Vasculogenic mimicry in the glioma samples was determined by dual staining for endothelial marker CD34 and periodic acid–Schiff (PAS). Tumor samples were also immunohistochemically stained for Ki-67, VEGF, COX-2 and MMP-9. The association between VM and the clinical characteristics of the patients were analyzed. A Kaplan–Meier survival analysis and log-rank tests were performed to compare survival times of the patients. Vasculogenic mimicry was present in 13 out of 101 samples. The higher grade gliomas had a higher incidence of VM than that of lower grade gliomas (P = 0.006). Vasculogenic mimicry channels were associated with the expression of COX-2 and MMP-9 (P < 0.05). While there was no association between the existence of VM and the sex, age and preoperative epilepsy of the patients, or expression of Ki-67 and VEGF. However, patients with VM-positive gliomas survived a shorter period of time than those with VM negative gliomas (P = 0.027). Interestingly, in high-grade gliomas, the level of microvascular density was lower in VM positive tumors than those VM negative tumors (P = 0.039). Our results suggest that VM channels in gliomas correlate with increasing malignancy and higher aggressiveness, and may provide a complementation to the tumor’s blood supply, especially in less vascularized regions, which may aid in the identification of glioma patients with a poorer prognosis.

Vasculogenic mimicry-potential target for glioblastoma therapy: an in vitro and in vivo study

Glioblastoma is one of the most angiogenic human tumors and characterized by microvascular proliferations. A better understanding of glioblastoma vasculature is needed to optimize anti-angiogenic therapy that has shown a promising but incomplete efficacy. The present study examined 48 glioblastomas by CD34 endothelial marker periodic acid-Schiff (PAS) dual staining and found non-endothelial cell-lined blood vessels that were formed by tumor cells (vasculogenic mimicry, VM) existing in a fraction of these tumors. We hypothesized that CD133-positive glioblastoma stem-like cells (GSCs) may play a pivotal role in glioblastoma VM formation and then demonstrated in vitro and in vivo that a subset of GSCs were capable of vasculogenesis. Moreover, we found that several growth factors involved in normal angiogenesis were expressed in GSCs. We describe here a new mechanism of alternative glioblastoma vascularization and open a new perspective for the anti-vascular treatment strategy.

The chromomycin CmmA acetyltransferase: a membrane-bound enzyme as a tool for increasing structural diversity of the antitumour mithramycin

Mithramycin and chromomycin A₃ are two structurally related antitumour compounds, which differ in the glycosylation profiles and functional group substitutions of the sugars. Chromomycin contains two acetyl groups, which are incorporated during the biosynthesis by the acetyltransferase CmmA in Streptomyces griseus ssp. griseus. A bioconversion strategy using an engineered S. griseus strain generated seven novel acetylated mithramycins. The newly formed compounds were purified and characterized by MS and NMR. These new compounds differ from their parental compounds in the presence of one, two or three acetyl groups, attached at 3E, 4E and/or 4D positions. All new mithramycin analogues showed antitumour activity at micromolar of lower concentrations. Some of the compounds showed improved activities against glioblastoma or pancreas tumour cells. The CmmA acetyltransferase was located in the cell membrane and was shown to accept several acyl‐CoA substrates. All these results highlight the potential of CmmA as a tool to create structural diversity in these antitumour compounds.

[Systematic review of stereotactic radiotherapy for high-grade gliomas]

The purpose of this literature systematic review was the use of stereotactic radiotherapy in glioma. Research was performed in Medline/PubMed and associated references found in published articles without publication date limit. The quality of series is variable and many biases can be evidenced. Only two randomized trials have been published using stereotactic radiotherapy for up-front treatment. There is a lack of evidence of survival advantages to use this treatment at the time of diagnosis or relapse. There is also insufficient evidence regarding the benefice/harms in the use of stereotactic fractionated radiation therapy for patients with glioma. No recommendations can be enounced. Stereotactic irradiation as boost in primary diagnosed glioma or relapsed tumour is not associated with survival improvement. For relapsed patients, treatment needs to be discussed according to the other treatment options.

Controversies concerning the application of brachytherapy in central nervous system tumors

INTRODUCTION

Brachytherapy (BRT) is defined as a therapy technique where a radioactive source is placed a short distance from or within the tumor being treated. Much expectation has been placed on its efficacy to improve the outcome for patients with central nervous system (CNS) tumors due to the initial promising results from single institution retrospective studies. However, these optimistic findings have been highly debated since the selection criteria itself is preferable to other therapeutic modalities. The fact that BRT demonstrated no significant survival advantage in two prospective studies, together with the emerging role of stereotactic convergence therapy as a promising alternative, has further decreased the enthusiasm for BRT. Despite all the negative aspects, BRT continues to be conducted for the management of CNS tumors including gliomas, meningiomas and brain metastases.

MATERIAL AND METHODS

As many controversies have been aroused concerning the experience and future application of BRT, this article reviews the existing heterogeneities in terms of implants choice, optimal dose rate, targeting volume, timing of BRT, patients selection, substantial efficacy, BRT in comparison with stereotactic convergence therapy techniques and BRT in combination with other treatment modalities (data were identified by Pubmed searches).

RESULTS AND CONCLUSION

Though it is inconvincible to argue for the routine use of BRT, BRT may provide a choice for patients with large recurrent or inoperable deep-seated tumors, especially with the Glia-site technique. Radiotherapies including BRT may hold more promise if biologic mechanisms of radiation could be better understand and biologic modifications could be added in clinical trials.

Role of stereotactic radiosurgery and fractionated stereotactic radiotherapy for the treatment of recurrent glioblastoma multiforme

Glioblastoma multiforme (GBM) is a devastating malignant brain tumor characterized by resistance to available therapeutic approaches and relentless malignant progression that includes widespread intracranial invasion, destruction of normal brain tissue, progressive disability, and death. Stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (fSRT) are increasingly used in patients with recurrent GBM to complement traditional treatments such as resection, conventional external beam radiotherapy, and chemotherapy. Both SRS and fSRT are powerful noninvasive therapeutic modalities well suited to treat focal neoplastic lesions through the delivery of precise, highdose radiation. Although no randomized clinical trials have been performed, a variety of retrospective studies have been focused on the use of SRS and fSRT for recurrent GBMs. In addition, state-of-the-art neuroimaging techniques, such as MR spectroscopic imaging, diffusion tensor tractography, and nuclear medicine imaging, have enhanced treatment planning methods leading to potentially improved clinical outcomes. In this paper the authors reviewed the current applications and efficacy of SRS and fSRT in the treatment of GBM, highlighting the value of these therapies for recurrent focal disease.

Integrated-boost IMRT or 3-D-CRT using FET-PET based auto-contoured target volume delineation for glioblastoma multiforme--a dosimetric comparison

Background

Biological brain tumor imaging using O-(2-[¹⁸F]fluoroethyl)-L-tyrosine (FET)-PET combined with inverse treatment planning for locally restricted dose escalation in patients with glioblastoma multiforme seems to be a promising approach.

The aim of this study was to compare inverse with forward treatment planning for an integrated boost dose application in patients suffering from a glioblastoma multiforme, while biological target volumes are based on FET-PET and MRI data sets.

Methods

In 16 glioblastoma patients an intensity-modulated radiotherapy technique comprising an integrated boost (IB-IMRT) and a 3-dimensional conventional radiotherapy (3D-CRT) technique were generated for dosimetric comparison. FET-PET, MRI and treatment planning CT (P-CT) were co-registrated. The integrated boost volume (PTV1) was auto-contoured using a cut-off tumor-to-brain ratio (TBR) of ≥ 1.6 from FET-PET. PTV2 delineation was MRI-based. The total dose was prescribed to 72 and 60 Gy for PTV1 and PTV2, using daily fractions of 2.4 and 2 Gy.

Results

After auto-contouring of PTV1 a marked target shape complexity had an impact on the dosimetric outcome. Patients with 3-4 PTV1 subvolumes vs. a single volume revealed a significant decrease in mean dose (67.7 vs. 70.6 Gy). From convex to complex shaped PTV1 mean doses decreased from 71.3 Gy to 67.7 Gy. The homogeneity and conformity for PTV1 and PTV2 was significantly improved with IB-IMRT. With the use of IB-IMRT the minimum dose within PTV1 (61.1 vs. 57.4 Gy) and PTV2 (51.4 vs. 40.9 Gy) increased significantly, and the mean EUD for PTV2 was improved (59.9 vs. 55.3 Gy, p < 0.01). The EUD for PTV1 was only slightly improved (68.3 vs. 67.3 Gy). The EUD for the brain was equal with both planning techniques.

Conclusion

In the presented planning study the integrated boost concept based on inversely planned IB-IMRT is feasible. The FET-PET-based automatically contoured PTV1 can lead to very complex geometric configurations, limiting the achievable mean dose in the boost volume. With IB-IMRT a better homogeneity and conformity, compared to 3D-CRT, could be achieved.