Survival of human glioma cells treated with various combination of temozolomide and X-rays

ATR inhibition using gartisertib enhances cell death and synergises with temozolomide and radiation in patient-derived glioblastoma cell lines

Glioblastoma cells can restrict the DNA-damaging effects of temozolomide (TMZ) and radiation therapy (RT) using the DNA damage response (DDR) mechanism which activates cell cycle arrest and DNA repair pathways. Ataxia-telangiectasia and Rad3-Related protein (ATR) plays a pivotal role in the recognition of DNA damage induced by chemotherapy and radiation causing downstream DDR activation. Here, we investigated the activity of gartisertib, a potent ATR inhibitor, alone and in combination with TMZ and/or RT in 12 patient-derived glioblastoma cell lines. We showed that gartisertib alone potently reduced the cell viability of glioblastoma cell lines, where sensitivity was associated with the frequency of DDR mutations and higher expression of the G2 cell cycle pathway. ATR inhibition significantly enhanced cell death in combination with TMZ and RT and was shown to have higher synergy than TMZ+RT treatment. MGMT promoter unmethylated and TMZ+RT resistant glioblastoma cells were also more sensitive to gartisertib. Analysis of gene expression from gartisertib treated glioblastoma cells identified the upregulation of innate immune-related pathways. Overall, this study identifies ATR inhibition as a strategy to enhance the DNA-damaging ability of glioblastoma standard treatment, while providing preliminary evidence that ATR inhibition induces an innate immune gene signature that warrants further investigation.

Biophysical Modeling of the Ionizing Radiation Influence on Cells Using the Stochastic (Monte Carlo) and Deterministic (Analytical) Approaches

This review article describes our simplified biophysical model for the response of a group of cells to ionizing radiation. The model, which is a product of 10 years of studies, acts as (a) a comprehensive stochastic approach based on the Monte Carlo simulation with a probability tree and (b) the thereof derived detailed deterministic models describing the selected biophysical and radiobiological phenomena in an analytical manner. Specifically, the presented model describes effects such as the risk of neoplastic transformation of cells relative to the absorbed radiation dose, the dynamics of tumor development, the priming dose effect (also called the Raper-Yonezawa effect) based on the introduced adaptive response approach, and the bystander effect. The model is also modifiable depending on users' potential needs.

Identification of a novel cuproptosis-related gene signature and integrative analyses in patients with lower-grade gliomas

Background

Cuproptosis is a newly discovered unique non-apoptotic programmed cell death distinguished from known death mechanisms like ferroptosis, pyroptosis, and necroptosis. However, the prognostic value of cuproptosis and the correlation between cuproptosis and the tumor microenvironment (TME) in lower-grade gliomas (LGGs) remain unknown.

Methods

In this study, we systematically investigated the genetic and transcriptional variation, prognostic value, and expression patterns of cuproptosis-related genes (CRGs). The CRG score was applied to quantify the cuproptosis subtypes. We then evaluated their values in the TME, prognostic prediction, and therapeutic responses in LGG. Lastly, we collected five paired LGG and matched normal adjacent tissue samples from Sun Yat-sen University Cancer Center (SYSUCC) to verify the expression of signature genes by quantitative real-time PCR (qRT-PCR) and Western blotting (WB).

Results

Two distinct cuproptosis-related clusters were identified using consensus unsupervised clustering analysis. The correlation between multilayer CRG alterations with clinical characteristics, prognosis, and TME cell infiltration were observed. Then, a well-performed cuproptosis-related risk model (CRG score) was developed to predict LGG patients' prognosis, which was evaluated and validated in two external cohorts. We classified patients into high- and low-risk groups according to the CRG score and found that patients in the low-risk group showed significantly higher survival possibilities than those in the high-risk group (P<0.001). A high CRG score implies higher TME scores, more significant TME cell infiltration, and increased mutation burden. Meanwhile, the CRG score was significantly correlated with the cancer stem cell index, chemoradiotherapy sensitivity-related genes and immune checkpoint genes, and chemotherapeutic sensitivity, indicating the association with CRGs and treatment responses. Univariate and multivariate Cox regression analyses revealed that the CRG score was an independent prognostic predictor for LGG patients. Subsequently, a highly accurate predictive model was established for facilitating the clinical application of the CRG score, showing good predictive ability and calibration. Additionally, crucial CRGs were further validated by qRT-PCR and WB.

Conclusion

Collectively, we demonstrated a comprehensive overview of CRG profiles in LGG and established a novel risk model for LGG patients' therapy status and prognosis. Our findings highlight the potential clinical implications of CRGs, suggesting that cuproptosis may be the potential therapeutic target for patients with LGG.

Temozolomide – Just a Radiosensitizer?

Radiation concomitant with the DNA methylating drug temozolomide (TMZ) is the gold standard in the treatment of glioblastoma. In this adjuvant setting, TMZ is regarded to be a radiation sensitizer. However, similar to ionising radiation, TMZ induces DNA double-strand breaks and is itself a potent trigger of apoptosis, cellular senescence and autophagy, suggesting that radiation and TMZ act independently. Although cell culture experiments yielded heterogeneous results, some data indicate that the cytotoxic effect of radiation was only enhanced when TMZ was given before radiation treatment. Based on the molecular mechanism of action of TMZ, the importance of specific TMZ and radiation-induced DNA lesions, their repair as well as their interactions, possible scenarios for an additive or synergistic effect of TMZ and radiation are discussed, and suggestions for an optimal timing of radio-chemical treatments are proposed.

Treatment-induced shrinking of tumour aggregates: a nonlinear volume-filling chemotactic approach

Motivated by experimental observations in 3D/organoid cultures derived from glioblastoma, we propose a novel mechano-transduction mechanism where the introduction of a chemotherapeutic treatment induces mechanical changes at the cell level. We analyse the influence of these individual mechanical changes on the properties of the aggregates obtained at the population level. We employ a nonlinear volume-filling chemotactic system of partial differential equations, where the elastic properties of the cells are taken into account through the so-called squeezing probability, which depends on the concentration of the treatment in the extracellular microenvironment. We explore two scenarios for the effect of the treatment: first, we suppose that the treatment acts only on the mechanical properties of the cells and, in the second one, we assume it also prevents cell proliferation. We perform a linear stability analysis which enables us to identify the ability of the system to create patterns and fully characterize their size. Moreover, we provide numerical simulations in 1D and 2D that illustrate the shrinking of the aggregates due to the presence of the treatment.

Short delay in initiation of radiotherapy for patients with glioblastoma-effect of concurrent chemotherapy: a secondary analysis from the NRG Oncology/Radiation Therapy Oncology Group database

Background

We previously reported the unexpected finding of significantly improved survival for newly diagnosed glioblastoma in patients when radiation therapy (RT) was initiated later (>4 wk post-op) compared with earlier (≤2 wk post-op). In that analysis, data were analyzed from 2855 patients from 16 NRG Oncology/Radiotherapy Oncology Group (RTOG) trials conducted prior to the era of concurrent temozolomide (TMZ) with RT. We now report on 1395 newly diagnosed glioblastomas from 2 studies, treated with RT and concurrent TMZ followed by adjuvant TMZ. Our hypothesis was that concurrent TMZ has a synergistic/radiosensitizing mechanism, making RT timing less significant.

Methods

Data from patients treated with TMZ-based chemoradiation from NRG Oncology/RTOG 0525 and 0825 were analyzed. An analysis comparable to our prior study was performed to determine whether there was still an impact on survival by delaying RT. Overall survival (OS) was investigated using the Kaplan-Meier method and Cox proportional hazards model. Early progression (during time of diagnosis to 30 days after RT completion) was analyzed using the chi-square test.

Results

Given the small number of patients who started RT early following surgery, comparisons were made between >4 and ≤4 weeks delay of radiation from time of operation. There was no statistically significant difference in OS (hazard ratio = 0.93; P = 0.29; 95% CI: 0.80-1.07) after adjusting for known prognostic factors (recursive partitioning analysis and O6-methylguanine-DNA methyltransferase methylation status). Similarly, the rate of early progression did not differ significantly (P = 0.63).

Conclusions

We did not observe a significant prognostic influence of delaying radiation when given concurrently with TMZ for newly diagnosed glioblastoma. The effects of early (1-3 wk post-op) or late (>5 wk) initiation of radiation tested in our prior study could not be replicated.

A Phase II Trial of Concurrent Temozolomide and Hypofractionated Stereotactic Radiotherapy for Complex Brain Metastases

PURPOSE

Complex brain metastases (BMs), such as large lesions, lesions within or close to eloquent locations, or multiple recurrent/progressive BMs, remain the most challenging forms of brain cancer because of decreased intracranial control rates and poor survival. In the present study, we report the results from a single institutional phase II trial of concurrent temozolomide (TMZ) with hypofractionated stereotactic radiotherapy (HFSRT) in patients with complex brain metastases, including assessment of its feasibility and toxicity.

PATIENTS AND METHODS

Fifty-four patients with histologically proven primary cancer and complex BMs were enrolled between 2010 and 2015. All the patients were treated with concurrent HFSRT and TMZ (administrated orally at a dosage of 75 mg/m² per day for at least 20 days). The primary endpoint was overall survival (OS).

RESULTS

The median follow-up time was 30.6 months. The local control rates at 1 and 2 years were 96% and 82%, respectively. The median OS was 17.4 months (95% confidence interval [CI], 12.6-22.2), and the OS rates at 1 and 2 years were 65% (95% CI, 52%-78%) and 33% (19%-47%). Only six patients (15.8%) died of intracranial disease. The median brain metastasis-specific survival was 46.9 months (95% CI, 35.5-58.4). Treatment-related grade 3-4 adverse events were rare and included one grade 3 hematological toxicity and two grade 3 liver dysfunctions.

CONCLUSION

Treatment using HFSRT concurrent with TMZ was well tolerated and could significantly extend OS compared with historical controls in complex BMs. Large randomized clinical trials are warranted. Trial registration ID: NCT02654106.

IMPLICATIONS FOR PRACTICE

The treatment using hypofractionated stereotactic radiotherapy concurrent with temozolomide appeared to be safe and could significantly extend overall survival compared with historical control in complex brain metastases. Large randomized clinical trials are warranted to verify our results.

Temozolomide and Radiotherapy as First-Line Treatment of High-Grade Gliomas

Aims and background

Temozolomide, a novel alkylating agent, has shown promising results in the treatment of patients with high-grade gliomas, when used as single agent as well as in combination with radiation therapy.

Materials and methods

In this report we retrospectively reviewed the clinical outcome of 128 consecutive patients with a diagnosis of high-grade gliomas referred to our Institutions from April 1994 to November 2001. The first 64 patients were treated with radiotherapy alone and the other 64 with a combination of radiotherapy and temozolomide (31 with radiotherapy and adjuvant temozolomide and 33 with radiotherapy and concomitant temozolomide followed by adjuvant temozolomide).

Results

Grade 3 hematological toxicity was scored in 9% of 64 patients treated with radiotherapy and temozolomide. No grade 4 hematological toxicity was reported, and the other acute side effects observed were mild or easily controlled with medications. Age, histology and administration of temozolomide were statistically significant prognostic factors associated with better 2-year overall survival. In contrast, we did not observe a significant difference in overall survival between adjuvant and concomitant/adjuvant temozolomide administration.

Conclusions

We report the favorable results of a schedule combining radiotherapy and temozolomide in the treatment of patients with high-grade gliomas. The literature data and above all the findings of the phase III EORTC-NCIC 26981 trial suggest that actually the schedule can be used routinely in clinical practice. Further clinical studies, using temozolomide in combination with other agents, are required.

Outcome of Newly Diagnosed Glioblastoma Patients Treated by Radiotherapy plus Concomitant and Adjuvant Temozolomide: A Long-Term Analysis

Aims and background

Glioblastoma is the most common primary brain tumor in adults. The standard treatment is surgery and radiotherapy. In this study, the results of radiotherapy plus concomitant and adjuvant temozolomide are reported. In addition, the efficiency of adjuvant temozolomide is evaluated.

Methods and study design

Forty-one patients were analyzed. All patients received radiotherapy (2 Gy daily fractionation dose, median 60 Gy total doses) and concomitant temozolomide (at a daily dose of 75 mg/m2/day, 7 days per week) after surgery. Thirty-one patients received an average of 6 cycles (range, 1–8 cycles) of adjuvant temozolomide after radiotherapy, every 28 days for 5 days at a dose of 200 mg/m2/day. The primary end point was overall survival.

Results

The median overall survival was 16.7 months. The overall survival significantly increased in the adjuvant temozolomide group compared to the group with no adjuvant therapy (18.9 vs 9.8 months). The difference in overall survival between adjuvant temozolomide cycles of ≤ and >3 was significant (8.7 vs 20 months). On multivariate analyses, the important prognostic factors were type of surgery and application of adjuvant temozolomide for at least 4 cycles. Grade III/IV toxicity was seen in 4% and 6.5% of patients during concomitant and adjuvant therapy, respectively.

Conclusions

The study confirmed the effectiveness of radiotherapy plus temozolomide in newly diagnosed glioblastoma. It was established that the application of adjuvant temozolomide for at least 4 cycles is required to obtain a benefit from adjuvant therapy. However, further studies are needed to confirm these data.

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.

Temozolomide during radiotherapy of glioblastoma multiforme : Daily administration improves survival

BACKGROUND

Temozolomide-(TMZ)-based chemoradiotherapy defines the current gold standard for the treatment of newly diagnosed glioblastoma. Data regarding the influence of TMZ dose density during chemoradiotherapy are currently not available. We retrospectively compared outcomes in patients receiving no TMZ, TMZ during radiotherapy on radiotherapy days only, and TMZ constantly 7 days a week.

PATIENTS AND METHODS

From 2002-2012, a total of 432 patients with newly diagnosed glioblastoma received radiotherapy in our department: 118 patients had radiotherapy alone, 210 had chemoradiotherapy with TMZ (75 mg/m²) daily (7/7), and 104 with TMZ only on radiotherapy days (5/7). Radiotherapy was applied to a total dose of 60 Gy.

RESULTS

Median survival after radiotherapy alone was 9.1 months, compared to 12.6 months with 5/7-TMZ and to 15.7 months with 7/7-TMZ. The 1‑year survival rates were 33, 52, and 64%, respectively. Kaplan-Meier analysis showed a significant improvement of TMZ-7/7 vs. 5/7 (p = 0.01 by the log-rank test), while 5/7-TMZ was still superior to no TMZ at all (p = 0.02). Multivariate Cox regression showed a significant influence of TMZ regimen (p = 0.009) on hazard rate (+58% between groups) even in the presence of confounding factors age, sex, resection status, and radiotherapy dose concept.

CONCLUSION

Our results confirm the findings of the EORTC/NCIC trial. It seems that also a reduced TMZ scheme can at first prolong the survival of glioblastoma patients, but not as much as the daily administration.

A phase II study of bevacizumab and erlotinib after radiation and temozolomide in MGMT unmethylated GBM patients

Survival for glioblastoma (GBM) patients with an unmethyated MGMT promoter in their tumor is generally worse than methylated MGMT tumors, as temozolomide (TMZ) response is limited. How to better treat patients with unmethylated MGMT is unknown. We performed a trial combining erlotinib and bevacizumab in unmethylated GBM patients after completion of radiation (RT) and TMZ. GBM patients with an unmethylated MGMT promoter were trial eligible. Patient received standard RT (60 Gy) and TMZ (75 mg/m2 × 6 weeks) after surgical resection of their tumor. After completion of RT they started erlotinib 150 mg daily and bevacizumab 10 mg/kg every 2 weeks until progression. Imaging evaluations occurred every 8 weeks. The primary endpoint was overall survival. Of the 48 unmethylated patients enrolled, 46 were evaluable (29 men and 17 women); median age was 55.5 years (29-75) and median KPS was 90 (70-100). All patients completed RT with TMZ. The median number of cycles (1 cycle was 4 weeks) was 8 (2-47). Forty-one patients either progressed or died with a median progression free survival of 9.2 months. At a follow up of 33 months the median overall survival was 13.2 months. There were no unexpected toxicities and most observed toxicities were categorized as CTC grade 1 or 2. The combination of erlotinib and bevacizumab is tolerable but did not meet our primary endpoint of increasing survival. Importantly, more trials are needed to find better therapies for GBM patients with an unmethylated MGMT promoter.

Dihydropyrimidine Dehydrogenase Is a Prognostic Marker for Mesenchymal Stem Cell-Mediated Cytosine Deaminase Gene and 5-Fluorocytosine Prodrug Therapy for the Treatment of Recurrent Gliomas

We investigated a therapeutic strategy for recurrent malignant gliomas using mesenchymal stem cells (MSC), expressing cytosine deaminase (CD), and prodrug 5-Fluorocytosine (5-FC) as a more specific and less toxic option. MSCs are emerging as a novel cell therapeutic agent with a cancer-targeting property, and CD is considered a promising enzyme in cancer gene therapy which can convert non-toxic 5-FC to toxic 5-Fluorouracil (5-FU). Therefore, use of prodrug 5-FC can minimize normal cell toxicity. Analyses of microarrays revealed that targeting DNA damage and its repair is a selectable option for gliomas after the standard chemo/radio-therapy. 5-FU is the most frequently used anti-cancer drug, which induces DNA breaks. Because dihydropyrimidine dehydrogenase (DPD) was reported to be involved in 5-FU metabolism to block DNA damage, we compared the survival rate with 5-FU treatment and the level of DPD expression in 15 different glioma cell lines. DPD-deficient cells showed higher sensitivity to 5-FU, and the regulation of DPD level by either siRNA or overexpression was directly related to the 5-FU sensitivity. For MSC/CD with 5-FC therapy, DPD-deficient cells such as U87MG, GBM28, and GBM37 showed higher sensitivity compared to DPD-high U373 cells. Effective inhibition of tumor growth was also observed in an orthotopic mouse model using DPD- deficient U87MG, indicating that DPD gene expression is indeed closely related to the efficacy of MSC/CD-mediated 5-FC therapy. Our results suggested that DPD can be used as a biomarker for selecting glioma patients who may possibly benefit from this therapy.

Is there a role for early chemotherapy in the management of pituitary adenomas?

Pituitary adenomas are benign intracranial neoplasms that are frequently well-controlled with standard treatments that include surgical resection, radiotherapy, and agents that modulate hormonal excess. Unfortunately, a subset of patients remains uncontrolled or develops complications from these interventions. For these patients, chemotherapy is an additional treatment option that could improve outcomes. Temozolomide is an oral chemotherapy with a favorable side-effect profile that has shown activity against pituitary adenomas. Its non-overlapping toxicity and ability to induce rapid tumor regression renders it a potentially important adjunctive treatment. In patients with tumors that cannot be optimally addressed with standard treatments, there may be a role for early initiation of temozolomide.

Treatment of recurrent metastatic uterine leiomyosarcoma of the spine: a multimodality approach using resection, radiosurgery, and chemotherapy

The authors describe the case of a patient who initially presented with uterine leiomyosarcoma (LMS) that later metastasized to the spine. The patient was treated at another institution for her primary uterine LMS, undergoing resection followed by adjuvant chemotherapy. After several years of disease remission, the patient presented in January 2011 to the authors' institution with recurrent uterine LMS metastatic to the spine, which has been treated with multiple therapeutic modalities in a combination of surgery, radiosurgery, and chemotherapy. As a result of this approach, the patient has been progression free for 35 months since her presentation (April 2011 to March 2014). We herein describe our experience treating this patient with recurrent uterine LMS of the spine and suggest that patients with recurrent uterine LMSs should be considered for treatment using a multimodality approach with emphasis on enrollment into clinical trials.

Temozolomide and radiotherapy versus radiotherapy alone in high grade gliomas: a very long term comparative study and literature review

Temozolomide (TMZ) is the first line drug in the care of high grade gliomas. The combined treatment of TMZ plus radiotherapy is more effective in the care of brain gliomas then radiotherapy alone. Aim of this report is a survival comparison, on a long time (>10 years) span, of glioma patients treated with radiotherapy alone and with radiotherapy + TMZ.

MATERIALS AND METHODS

In this report we retrospectively reviewed the outcome of 128 consecutive pts with diagnosis of high grade gliomas referred to our institutions from April 1994 to November 2001. The first 64 pts were treated with RT alone and the other 64 with a combination of RT and adjuvant or concomitant TMZ.

RESULTS

Grade 3 (G3) haematological toxicity was recorded in 6 (9%) of 64 pts treated with RT and TMZ. No G4 haematological toxicity was observed. Age, histology, and administration of TMZ were statistically significant prognostic factors associated with 2 years overall survival (OS). PFS was for GBM 9 months, for AA 11.

CONCLUSIONS

The combination of RT and TMZ improves long term survival in glioma patients. Our results confirm the superiority of the combination on a long time basis.

INTRAGO: intraoperative radiotherapy in glioblastoma multiforme—a phase I/II dose escalation study

BACKGROUND

Glioblastoma multiforme (GBM) is the most frequent primary malignant brain tumor in adults. Despite multimodal therapies, almost all GBM recur within a narrow margin around the initial resected lesion. Thus, novel therapeutic intensification strategies must target both, the population of dispersed tumor cells around the cavity and the postoperative microenvironment. Intraoperative radiotherapy (IORT) is a pragmatic and effective approach to sterilize the margins from persistent tumor cells, abrogate post-injury proliferative stimuli and to bridge the therapeutic gap between surgery and radiochemotherapy. Therefore, we have set up INTRAGO, a phase I/II dose-escalation study to evaluate the safety and tolerability of IORT added to standard therapy in newly diagnosed GBM. In contrast to previous approaches, the study involves the application of isotropic low-energy (kV) x-rays delivered by spherical applicators, providing optimal irradiation properties to the resection cavity.

METHODS/DESIGN

INTRAGO includes patients aged 50 years or older with a Karnofsky performance status of at least 50% and a histologically confirmed (frozen sections) supratentorial GBM. Safety and tolerability (i.e., the maximum tolerated dose, MTD) will be assessed using a classical 3 + 3 dose-escalation design. Dose-limiting toxicities (DLT) are wound healing deficits or infections requiring surgical intervention, IORT-related cerebral bleeding or ischemia, symptomatic brain necrosis requiring surgical intervention and early termination of external beam radiotherapy (before the envisaged dose of 60 Gy) due to radiotoxicity. Secondary end points are progression-free and overall survival.

TRIAL REGISTRATION

The study is registered with clinicaltrials.gov, number: NCT02104882 (Registration Date: 03/26/2014).

Effects of single or combined treatments with radiation and chemotherapy on survival and danger signals expression in glioblastoma cell lines

The success of chemo- and radiotherapy in glioblastoma multiforme, the most common and lethal primary brain tumour, could rely on the induction of immunogenic tumour cell death and on the induction of anticancer immune response. In this study we investigated cell survival to single treatments or combination of X-rays and temozolomide in glioblastoma cell lines (T98G and U251MG) and we attempted to identify danger signals (HMGB1 and HSP70) released by dying cells in the microenvironment that could activate antitumour immunity contributing to the therapeutic efficacy of conventional treatments. Our data suggest that HSP70 translocates from cytoplasm to extracellular environment after an increase in radiation dose and HMGB1 translocates from the nucleus to the cytoplasm and subsequently is released into the extracellular space, confirming a role of these proteins as signals released after radiation-induced damage in glioblastoma cells. We also could state that TMZ had limited effectiveness in activating HMGB1 and HSP70 signalling and, instead, an adjuvant effect was observed in some combined treatments, depending on schedule, cell line, and timing. A big challenge in tumour therapy is, therefore, to identify the most beneficial combination and chronology of multiple treatment options to contribute to the improvement of the therapeutic outcome.

Role of radiotherapy in the treatment of gliomas

Malignant gliomas are challenging tumors that are often treated with a multimodality approach. This article focuses on the role of radiotherapy in the management of these tumors. The role of radiotherapy in low-grade gliomas remains controversial and this review focuses on the importance of prognostic factors, recent randomized trials involving radiotherapy, and toxicity from radiotherapy. In terms of high-grade gliomas, radiotherapy has a more established role and this review will address methods that have been evaluated in order to improve radiotherapy outcome. Improvements in radiotherapy delivery, tumor imaging and biologic modifiers may ultimately lead to improved outcome in the treatment of these difficult tumors.

Temozolomide in combination with carbon ion or photon irradiation in glioblastoma multiforme cell lines - does scheduling matter?

PURPOSE

To extend the application area of particle therapy with carbon ions the many already established treatment regimens for different tumor entities have to be taken into consideration. The present study investigates the effect of combined radiochemotherapy with temozolomide (TMZ) and high linear energy transfer (LET) irradiation with carbon ions versus photons.

MATERIALS AND METHODS

Clonogenic survival was analyzed for human glioma cell lines with different O6-methylguanine-DNA methyltransferase (MGMT) status, LN18 (MGMT+) and LN-229 (MGMT-), after exposure to different doses of either carbon ion or photon irradiation at different time points relative to TMZ application. Cell cycle distribution was measured by flow cytometry. MGMT status of the cell lines was verified by Western blot.

RESULTS

LN-18 and LN-229 reacted in accordance to their MGMT status with different sensitivity to TMZ treatment. Combined treatment with irradiation showed additive cytotoxic effects for both cell lines with low radiation doses but no radiosensitization. With increasing photon doses the combination effect was reduced, and the efficacy of the combined treatment was not dependent on administration schedule. Carbon ion irradiation showed the well known increased relative biological efficiency (RBE), overcame the above-mentioned antagonism and was also not schedule-dependent.

CONCLUSIONS

The in vitro effectiveness of TMZ in combined radiochemotherapy is independent of administration time or MGMT-expression. Both cell lines are significantly more sensitive to combined treatment with carbon ion radiation than to photon radiation but do not show any super-additive effects.

Five-year follow-up results for patients diagnosed with anaplastic astrocytoma and effectiveness of concomitant therapy with temozolomide for recurrent anaplastic astrocytoma

Background:

Anaplastic astrocytoma (AA; WHO grade-III) patients determination of prognostic factors helps generating multimodal therapy protocols. For this purpose, in the Baskent University, Adana Medical Research Center, specific characteristics of AA patients who have surgery were retrospectively investigated and factors which affect prognosis has been determined.

Patients and Methods:

Between January 2005 and 2009, 20 patients who have AA have been evaluated retrospectively. Totally, 20 patients had 31 operations. Sixteen patients had only adjuvant radiation therapy (RT). In the postoperative period, 8 patients received adjuvant RT. Nine of 10 patients with tumor recurrence received concomitant therapy with temozolomide (ConcT with TMZ) protocol. No adjuvant therapy protocol could be applied in three patients with poor general condition in the postoperative period.

Results:

Median survival for patients died was 16±17 months; one year survival was 75% and five year survival 25%. After univariate analysis, preoperative Karnofsky performance score (KPS) was ≥80 (P=0.005577^*), postoperative KPS was ≥80 (P=0.003825^*), type of tumor resection (P=0.001751^*), multiple operations (P=0.006233^*), and ConcT with TMZ protocol (P=0,005766^*) were all positive prognostic factors which extend the survival.

Conclusions:

The results of the multivariate analysis did not put forward an independent prognostic factor acting on the survival period (P>0.05).

Evaluation of poly (ADP-ribose) polymerase inhibitor ABT-888 combined with radiotherapy and temozolomide in glioblastoma

BACKGROUND

The cytotoxicity of radiotherapy and chemotherapy can be enhanced by modulating DNA repair. PARP is a family of enzymes required for an efficient base-excision repair of DNA single-strand breaks and inhibition of PARP can prevent the repair of these lesions. The current study investigates the trimodal combination of ABT-888, a potent inhibitor of PARP1-2, ionizing radiation and temozolomide(TMZ)-based chemotherapy in glioblastoma (GBM) cells.

METHODS

Four human GBM cell lines were treated for 5 h with 5 μM ABT-888 before being exposed to X-rays concurrently with TMZ at doses of 5 or 10 μM for 2 h. ABT-888's PARP inhibition was measured using immunodetection of poly(ADP-ribose) (pADPr). Cell survival and the different cell death pathways were examined via clonogenic assay and morphological characterization of the cell and cell nucleus.

RESULTS

Combining ABT-888 with radiation yielded enhanced cell killing in all four cell lines, as demonstrated by a sensitizer enhancement ratio at 50% survival (SER50) ranging between 1.12 and 1.37. Radio- and chemo-sensitization was further enhanced when ABT-888 was combined with both X-rays and TMZ in the O6-methylguanine-DNA-methyltransferase (MGMT)-methylated cell lines with a SER50 up to 1.44. This effect was also measured in one of the MGMT-unmethylated cell lines with a SER50 value of 1.30. Apoptosis induction by ABT-888, TMZ and X-rays was also considered and the effect of ABT-888 on the number of apoptotic cells was noticeable at later time points. In addition, this work showed that ABT-888 mediated sensitization is replication dependent, thus demonstrating that this effect might be more pronounced in tumour cells in which endogenous replication lesions are present in a larger proportion than in normal cells.

CONCLUSIONS

This study suggests that ABT-888 has the clinical potential to enhance the current standard treatment for GBM, in combination with conventional chemo-radiotherapy. Interestingly, our results suggest that the use of PARP inhibitors might be clinically significant in those patients whose tumour is MGMT-unmethylated and currently derive less benefit from TMZ.

Telomere targeting with a new G4 ligand enhances radiation-induced killing of human glioblastoma cells

The aim of this study was to test in vitro the efficacy of TAC, an original G-quadruplex ligand, as a potential radiosensitizing agent for glioblastoma multiforme (GBM). Two human radioresistant telomerase-positive GBM cell lines (SF763 and SF767) were analyzed, with and without TAC treatment, for telomere length, cell proliferation, apoptosis, cell-cycle distribution, gene expression, cytogenetic aberrations, clonogenic survival assay, 53BP1 immunofluorescence staining, and γH2AX phosphorylation. We found that low concentrations of TAC (0.5 and 1 μmol/L) inhibited the proliferation of GBM cells in a concentration-dependent manner after only 1 week of treatment, with minimal effects on cell cycle and apoptosis. TAC treatment had no visible effect on average telomere length but modified expression levels of telomere-related genes (hTERT, TRF1, and TRF2) and induced concentration-dependent DNA damage response and dicentric chromosomes. Survival curves analysis showed that exposure to nontoxic, subapoptotic concentrations of TAC enhanced radiation-induced killing of GBM cells. Analysis of DNA repair after irradiation revealed delayed repair kinetics in GBM cells treated with TAC. Furthermore, the combined treatment (TAC and radiation) significantly increased the frequency of chromosomal aberrations as compared with radiation alone. These findings provide the first evidence that exposure to a G4 ligand radiosensitizes human glioblastoma cells and suggest the prospect of future therapeutic applications.

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.

Can drugs enhance hypofractionated radiotherapy? A novel method of modeling radiosensitization using in vitro data

PURPOSE

Hypofractionated radiotherapy (hRT) is being explored for a number of malignancies. The potential benefit of giving concurrent chemotherapy with hRT is not known. We sought to predict the effects of combined modality treatments by using mathematical models derived from laboratory data.

METHODS AND MATERIALS

Data from 26 published clonogenic survival assays for cancer cell lines with and without the use of radiosensitizing chemotherapy were collected. The first three data points of the RT arm of each assay were used to derive parameters for the linear quadratic (LQ) model, the multitarget (MT) model, and the generalized linear quadratic (gLQ) model. For each assay and model, the difference between the predicted and observed surviving fractions at the highest tested RT dose was calculated. The gLQ model was fitted to all the data from each RT cell survival assay, and the biologically equivalent doses in 2-Gy fractions (EQD2s) of clinically relevant hRT regimens were calculated. The increase in cell kill conferred by the addition of chemotherapy was used to estimate the EQD2 of hRT along with a radiosensitizing agent. For comparison, this was repeated using conventionally fractionated RT regimens.

RESULTS

At a mean RT dose of 8.0 Gy, the average errors for the LQ, MT, and gLQ models were 1.63, 0.83, and 0.56 log units, respectively, favoring the gLQ model (p < 0.05). Radiosensitizing chemotherapy increased the EQD2 of hRT schedules by an average of 28% to 82%, depending on disease site. This increase was similar to the gains predicted for the addition of chemotherapy to conventionally fractionated RT.

CONCLUSIONS

Based on published in vitro assays, the gLQ equation is superior to the LQ and MT models in predicting cell kill at high doses of RT. Modeling exercises demonstrate that significant increases in biologically equivalent dose may be achieved with the addition of radiosensitizing agents to hRT. Clinical study of this approach is warranted.

Valproic acid sensitizes human glioma cells for temozolomide and γ-radiation

Temozolomide (TMZ) is given in addition to radiotherapy in glioma patients, but its interaction with the commonly prescribed antiepileptic drug valproic acid (VPA) is largely unknown. Induction of DNA demethylation by VPA could potentially induce expression of the O(6)-methylguanine-DNA-methyltransferase (MGMT) protein, causing resistance to TMZ and thereby antagonizing its effect. Therefore, this study investigates the interaction between VPA, TMZ, and γ-radiation. Two glioma cell lines were used that differ in TMZ sensitivity caused by the absence (D384) or presence (T98) of the MGMT protein. VPA was administered before (24/48 h) or after (24 h) single doses of γ-radiation; or, after 24 h, VPA treatment was accompanied by a single dose of TMZ for another 24 h. For trimodal treatment the combination of VPA and TMZ was followed by single doses of γ-radiation. In both cell lines VPA caused enhancement of the radiation response after preincubation (DMF(0.2) 1.4 and 1.5) but not after postirradiation (DMF(0.2) 1.1 and 1.0). The combination of VPA and TMZ caused enhanced cytotoxicity (DMF(0.2) 1.7) in both the TMZ-sensitive cell line (D384) and the TMZ-resistant cell line (T98). The combination of VPA and TMZ caused a significant radiation enhancement (DMF(0.2) 1.9 and 1.6) that was slightly more effective than that of VPA alone. VPA does not antagonize the cytotoxic effects of TMZ. Preincubation with VPA enhances the effect of both γ-radiation and TMZ, in both a TMZ-sensitive and a TMZ-resistant human glioma cell line. VPA combined with TMZ may lead to further enhancement of the radiation response.

Patterns of failure for glioblastoma multiforme following concurrent radiation and temozolomide

PURPOSE

To analyse patterns of failure in patients with glioblastoma multiforme treated with concurrent radiation and temozolomide.

MATERIALS AND METHODS

A retrospective review of patients treated with concurrent radiation and temozolomide was performed. Twenty patients treated at the University of Alabama at Birmingham, with biopsy-proven disease, documented disease progression after treatment, and adequate radiation dosimetry and imaging records were included in the study. Patients generally received 46 Gy to the primary tumour and surrounding oedema plus 1 cm, and 60 Gy to the enhancing tumour plus 1 cm. MRIs documenting failure after therapy were fused to the original treatment plans. Contours of post-treatment tumour volumes were generated from MRIs showing tumour failure and were overlaid onto the original isodose curves. The recurrent tumours were classified as in-field, marginal or regional. Recurrences were also evaluated for distant failure.

RESULTS

Of the 20 documented failures, all patients had some component of failure at the primary site. Eighteen patients (90%) failed in-field, 2 patients (10%) had marginal failures, and no regional failures occurred. Four patients (20%) had a component of distant failure in which an independent satellite lesion was located completely outside of the 95% isodose curve.

CONCLUSIONS

Radiation concurrent with temozolomide appears to be associated with a moderate risk of distant brain failure in addition to the high rate of local failure. The risk of distant failure was consistent with that observed with radiation alone, suggesting that temozolomide does not act to reduce distant brain failure but to improve local control.

Rad51 inhibition is an effective means of targeting DNA repair in glioma models and CD133+ tumor-derived cells

High grade gliomas (HGGs) are characterized by resistance to radiotherapy and chemotherapy. Targeting Rad51-dependent homologous recombination repair may be an effective target for chemo- and radiosensitization. In this study we assessed the role of Rad51-dependent repair on sensitivity to radiation and temozolomide (TMZ) as single agents or in combination. Repair protein levels in established glioma cell lines, early passage glioblastoma multiforme (GBM) cell lines, and normal human astrocytes (NHAs) were measured using western blot. Viability and clonogenic survival assays were used to measure the effects of Rad51 knockdown with radiation (XR) and TMZ. Immunocytochemistry was used to evaluate kinetics of Rad51 and γ-H2AX repair foci. Immunohistochemistry was used to assess Rad51 protein levels in glioma specimens. Repair proteins including Rad51 are upregulated in HGG cells compared with NHA. Established glioma cell lines show a dose-dependent increase in Rad51 foci formation after XR and TMZ. Rad51 levels are inversely correlated with radiosensitivity, and downregulation markedly increases the cytotoxicity of TMZ. Rad51 knockdown also promotes more residual γ-H2AX foci 24 h after combined treatment. Newly established GBM cell lines also have high Rad51 levels and are extremely sensitive to Rad51 knockdown. Clinical samples from recently resected gliomas of varying grades demonstrate that Rad51 levels do not correlate with tumor grade. Rad51-dependent repair makes a significant contribution to DNA repair in glioma cells and contributes to resistance to both XR and TMZ. Agents targeting Rad51-dependent repair would be effective adjuvants in standard combination regimens.

Temozolomide in malignant glioma

Glioblastoma multiforme WHO grade IV (GBM) is the most aggressive malignant glioma and the most frequent primary tumor of the central nervous system. The median survival of newly diagnosed GBM patients was between 9 to 12 months prior to treatment with temozolomide being introduced. Primary resection that is as complete as possible is recommended for malignant glioma. Conventional fractionated irradiation 55 to 60 gy with concomitant temozolomide followed by standard temozolomide 6 cycles (5/28) (EORTC/NCIC-regime published by R Stupp in 2005) is the standard of care for newly diagnosed GBM after surgery, independent of the methylation status of the MGM-T gene promoter. Age is no contraindication for treatment with temozolomide, although comorbidity and performance status have to be considered. For temozolomide naive GBM and astrocytoma grade III patients with disease progression, temozolomide is still the treatment of choice outside of clinical studies. A general consensus regarding the schedule of choice has not yet been achieved; so far the 5 out of 28 days regimen (5/28) is the standard of care in most countries. Patients with disease progression after standard temozolomide (5/28) are candidates for clinical studies. Outside of clinical studies, dose-dense (7/7), prolonged (21/28), or metronomic (28/28) temozolomide, or alternatively a nitrosourea-based regimen can be an option. The excellent toxicity profile of temozolomide allows for various combinations with antitumor agents. None of these combinations, however, have been demonstrated to be statistically significantly superior compared to temozolomide alone. The role of lower dosed, dose-dense, or continuous regimen with or without drug combination and the role of temozolomide for newly diagnosed astrocytoma grade III and low grade glioma still has to be determined.

Role of temozolomide in the treatment of newly diagnosed diffuse brainstem glioma in children: experience at a single institution

PURPOSE

The purpose of this study was to assess the efficacy of TMZ on diffuse brainstem glioma, either concomitant with radiotherapy or as an adjuvant treatment after radiotherapy in children.

METHODS AND MATERIALS

Eighteen children (median age at diagnosis was 8.3 years) meet the following criteria: (1) newly diagnosed diffuse brainstem glioma; (2) aged less than 18 years old, which were treated with TMZ at Taipei Veterans General Hospital from January 2004 to December 2008. They were divided into two groups according to treatment modalities: a radiotherapy alone followed by adjuvant TMZ (RT+TMZ) group received conventional radiation after initial diagnosis, and a concomitant chemoradiotherapy followed by adjuvant TMZ (CCRT+TMZ) group received concurrent chemotherapy during radiation with TMZ (75 mg/M(2)/day). After completion of the radiotherapy, TMZ (150 mg/M(2)) was administered once per day for five consecutive days for all enrolled patients in each 28-day cycle. We evaluated the progression-free survival in both groups of patients.

RESULTS

There were 10 patients in RT+TMZ group and eight in CCRT+TMZ group. All patients experienced progression of disease. Twelve patients (75%) died, and all deaths were attributed to the disease progression. The median progression-free survival (PFS) was 7.4 months for the RT+TMZ group and 6.4 months for the CCRT+TMZ group. The 6-month and 1-year PFS in the RT+TMZ group were 70% (SD 14%) and 30% (SD 14%), respectively, and in the CCRT+TMZ group, they were 50% (SD 17%) and 0%, respectively. The log-rank test in PFS between the two groups was not statistically significant.

CONCLUSIONS

In this study, CCRT with TMZ followed by adjuvant TMZ did not result in a better outcome when compared with RT alone followed by adjuvant TMZ. In addition, TMZ either as adjuvant therapy or as CCRT did not improve the prognosis of the patients with newly diagnosed diffuse brainstem glioma.

Determination of the methylation status of MGMT in different regions within glioblastoma multiforme

Epigenetic silencing of the MGMT gene through promoter methylation correlates with improved survival in Glioblastoma Multiforme (GBM) patients receiving concurrent chemoradiotherapy. Although the clinical benefit is primarily seen in patients with methylated MGMT promoter, some unmethylated patients also respond to Temozolomide. One possible explanation may be intratumoral heterogeneity. This study was designed to assess the methylation status of the MGMT promoter in different areas of GBM and determine if methylation status varied depending on the fixation technique (paraffin-embedding versus fresh frozen) used to store tissue. Using intraoperative navigation, biopsies were obtained from three distinct regions: the enhancing outer area, the non-enhancing inner core, and an area immediately outside the enhancing region. Only patients with GBM were included for evaluation and analysis. Samples taken from each area were divided with half stored by flash freezing and the other half stored using paraffin fixation. Methylation Specific-PCR (MS-PCR) was used for analysis of MGMT promoter methylation. Thirteen patients were included. Ten were male with a median age of 62 years. In each patient, samples were taken from the enhancing rim and the necrotic centre. However, it was not considered safe or feasible to obtain samples from the area immediately adjacent to the enhancing tumor rim in one case. All patients were homogeneous for methylation status throughout their tumor and tissue taken adjacent to it when frozen tissue was used. However, four patients had discrepancies in the MGMT promoter status between the frozen and paraffin-embedded blocks and one patient was not homogeneous within the tumor when paraffin-embedded tissue was used. MGMT promoter methylation status was homogeneous in all GBM tumors. Our observation that methylation status varied depending if the DNA was extracted from paraffin-embedded versus frozen tissue is concerning. Although the reason for this is unclear, we postulate that the timing from resection to fixation or the process of fixation itself may potentially alter methylation status in paraffin-embedded tumors.

Temozolomide: The evidence for its therapeutic efficacy in malignant astrocytomas

Introduction:

Malignant gliomas are a heterogeneous group of primary central nervous system neoplasms that represent less than 2% of all cancers yet carry a significant burden to society. They are frequently associated with considerable and progressive neurological disability and are ultimately intractable to all forms of treatment. Temozolomide (TMZ) is a new second generation DNA alkylating agent that has become part of malignant astrocytoma management paradigms because of its proven efficacy, ease of administration, and favorable toxicity profile.

Aims:

To review the role of TMZ in the management of malignant astrocytomas (World Health Organization grades III and IV) including newly diagnosed (n) and recurrent (r) anaplastic astrocytomas (AA) and glioblastomas.

Evidence review:

A series of pivotal clinical trials have established a role for TMZ in the treatment of malignant astrocytomas. A large phase II trial examining the role of TMZ in rAA showed a response rate of 35%, and a 6-month progression-free survival of 46%. This led to the accelerated approval of TMZ by the FDA and the EU for the treatment of rAA. Evidence for a role of TMZ in nAA is currently limited but research is ongoing in this area. The role of TMZ in the management of glioblastoma at the time of recurrence (rGBM) is less impressive but evidence for its activity was demonstrated in two large phase II trials that led to the approval of TMZ for this indication in Europe and Canada but not in the US. A recent large prospective randomized phase III trial showed that the addition of TMZ during and after radiation therapy (RT) in newly diagnosed (nGBM) patients prolonged median overall survival by 2.5 months; perhaps more importantly, the 2-year survival rate for patients receiving TMZ and RT was 26% compared with 10% for those receiving RT alone. Concurrent TMZ with RT followed by adjuvant TMZ has become the standard of care for nGBM patients. Based on the evidence presented in this trial, TMZ received approval from the FDA and the EU for patients with nGBM in 2005.

Place in therapy:

There is evidence to support the use of TMZ for the following diseases in the order of most to least convincing: nGBM, rAA, rGBM, and nAA. This order may quickly change as more trials are being designed and implemented, particularly with novel TMZ dosing schedules.

Minimally cytotoxic doses of temozolomide produce radiosensitization in human glioblastoma cells regardless of MGMT expression

Concurrent treatment with the methylating agent temozolomide during radiotherapy has yielded the first significant improvement in the survival of adult glioblastomas (GBM) in the last three decades. However, improved survival is observed in a minority of patients, most frequently those whose tumors display CpG methylation of the O(6)-methylguanine (O(6)-meG)-DNA methyltransferase (MGMT) promoter, and adult GBMs remain invariably fatal. Some, although not all, preclinical studies have shown that temozolomide can increase radiosensitivity in GBM cells that lack MGMT, the sole activity in human cells that removes O(6)-meG from DNA. Here, we systematically examined the temozolomide dose dependence of radiation killing in established GBM cell lines that differ in ability to remove O(6)-meG or tolerate its lethality. Our results show that minimally cytotoxic doses of temozolomide can produce dose-dependent radiosensitization in MGMT-deficient cells, MGMT-proficient cells, and MGMT-deficient cells that lack mismatch repair, a process that renders cells tolerant of the lethality of O(6)-meG. In cells that either possess or lack MGMT activity, radiosensitization requires exposure to temozolomide before but not after radiation and is accompanied by formation of double-strand breaks within 45 minutes of radiation. Moreover, suppressing alkyladenine-DNA glycosylase, the only activity in human cells that excises 3-methyladenine from DNA, reduces the temozolomide dose dependence of radiosensitization, indicating that radiosensitization is mediated by 3-methyladenine as well as by O(6)-meG. These results provide novel information on which to base further mechanistic study of radiosensitization by temozolomide in human GBM cells and to develop strategies to improve the outcome of concurrent temozolomide radiotherapy.

Canadian recommendations for the treatment of glioblastoma multiforme

Recommendation 1

Management of patients with glioblastoma multiforme (gbm) should be highly individualized and should take a multidisciplinary approach involving neuro-oncology, neurosurgery, radiation oncology, and pathology, to optimize treatment outcomes. Patients and caregivers should be kept informed of the progress of treatment at every stage.

Recommendation 2

Sufficient tissue should be obtained during surgery for cytogenetic analysis and, whenever feasible, for tumour banking.

Recommendation 3

Surgery is an integral part of the treatment plan, to establish a histopathologic diagnosis and to achieve safe, maximal, and feasible tumour resection, which may improve clinical signs and symptoms.

Recommendation 4

The preoperative imaging modality of choice is magnetic resonance imaging (mri) with gadolinium as the contrast agent. Other imaging modalities, such as positron emission tomography with [¹⁸F]-fluoro-deoxy-d-glucose, may also be considered in selected cases. Postoperative imaging (mri or computed tomography) is recommended within 72 hours of surgery to evaluate the extent of resection.

Recommendation 5

Postoperative external-beam radiotherapy is recommended as standard therapy for patients with gbm. The recommended dose is 60 Gy in 2-Gy fractions. The recommended clinical target volume should be identified with gadolinium-enhanced T1-weighted mri, with a margin in the order of 2–3 cm. Target volumes should be determined based on a postsurgical planning mri. A shorter course of radiation may be considered for older patients with poor performance status.

Recommendation 6

During rt, temozolomide 75 mg/m² should be administered concurrently for the full duration of radio-therapy, typically 42 days. Temozolomide should be given approximately 1 hour before radiation therapy, and at the same time on the days that no radiotherapy is scheduled.

Recommendation 7

Adjuvant temozolomide 150 mg/m², in a 5/28-day schedule, is recommended for cycle 1, followed by 5 cycles if well tolerated. Additional cycles may be considered in partial responders. The dose should be increased to 200 mg/m² at cycle 2 if well tolerated. Weekly monitoring of blood count is advised during chemoradiation therapy in patients with a low white blood cell count. Pneumocystis carinii pneumonia has been reported, and prophylaxis should be considered.

Recommendation 8

For patients with stable clinical symptoms during combined radiotherapy and temozolomide, completion of 3 cycles of adjuvant therapy is generally advised before a decision is made about whether to continue treatment, because pseudo-progression is a common phenomenon during this time. The recommended duration of therapy is 6 months. A longer duration may be considered in patients who show continuous improvement on therapy.

Recommendation 9

Selected patients with recurrent gbm may be candidates for repeat resection when the situation appears favourable based on an assessment of individual patient factors such as medical history, functional status, and location of the tumour. Entry into a clinical trial is recommended for patients with recurrent disease.

Recommendation 10

The optimal chemotherapeutic strategy for patients who progress following concurrent chemoradiation has not been determined. Therapeutic and clinical–molecular studies with quality of life outcomes are needed.

Differential Effects of the Proteasome Inhibitor NPI-0052 against Glioma Cells

Proteasome inhibitors are emerging as a new class of cancer therapeutics, and bortezomib has shown promise in the treatment of multiple myeloma and mantle cell lymphoma. However, bortezomib has failed to have an effect in preclinical models of glioma. NPI-0052 is a new generation of proteasome inhibitors with increased potency and strong inhibition of all three catalytic activities of the 26S proteasome. In this article, we test the antitumor efficacy of NPI-0052 against glioma, as a single agent and in combination with temozolomide and radiation using five different glioma lines. The intrinsic radiation sensitivities differed for all the lines and correlated with their PTEN expression status. In vitro, NPI-0052 showed a dose-dependent toxicity, and its combination with temozolomide resulted in radiosensitization of only the cell lines with a mutated p53. The effect of NPI-0052 as a single agent on glioma xenografts in vivo was only modest in controlling tumor growth, and it failed to radiosensitize the glioma xenografts to fractionated radiation. We conclude that NPI-0052 is not a suitable drug for the treatment of malignant gliomas despite its efficacy in other cancer types.

The neuropharmacokinetics of temozolomide in patients with resectable brain tumors: potential implications for the current approach to chemoradiation

PURPOSE

Intracerebral microdialysis (ICMD) is an accepted method for monitoring changes in neurochemistry from acute brain injury. The goal of this pilot study was to determine the feasibility of using ICMD to examine the neuropharmacokinetics of temozolomide in brain interstitium following oral administration.

EXPERIMENTAL DESIGN

Patients with primary or metastatic brain tumors had a microdialysis catheter placed in peritumoral brain tissue at the time of surgical debulking. Computerized tomography scan confirmed the catheter location. Patients received a single oral dose of temozolomide (150 mg/m2) on the first postoperative day, serial plasma and ICMD samples were collected over 24 hours, and temozolomide concentrations were determined by tandem mass spectrometry.

RESULTS

Nine patients were enrolled. Dialysate and plasma samples were successfully collected from seven of the nine patients. The mean temozolomide areas under the concentration-time curve (AUC) in plasma and brain interstitium were 17.1 and 2.7 microg/mL x hour, with an average brain interstitium/plasma AUC ratio of 17.8%. The mean peak temozolomide concentration in the brain was 0.6 +/- 0.3 microg/mL, and the mean time to reach peak level in brain was 2.0 +/- 0.8 hours.

CONCLUSIONS

The use of ICMD to measure the neuropharmacokinetics of systemically administered chemotherapy is safe and feasible. Concentrations of temozolomide in brain interstitium obtained by ICMD are consistent with published data obtained in a preclinical ICMD model, as well as from clinical studies of cerebrospinal fluid. However, the delayed time required to achieve maximum temozolomide concentrations in brain suggests that current chemoradiation regimens may be improved by administering temozolomide 2 to 3 hours before radiation.

Radiosensitizing effects of temozolomide observed in vivo only in a subset of O6-methylguanine-DNA methyltransferase methylated glioblastoma multiforme xenografts

PURPOSE

Concurrent temozolomide (TMZ) and radiation therapy (RT) followed by adjuvant TMZ is standard treatment for patients with glioblastoma multiforme (GBM), although the relative contribution of concurrent versus adjuvant TMZ is unknown. In this study, the efficacy of TMZ/RT was tested with a panel of 20 primary GBM xenografts.

METHODS AND MATERIALS

Mice with intracranial xenografts were treated with TMZ, RT, TMZ/RT, or placebo. Survival ratio for a given treatment/line was defined as the ratio of median survival for treatment vs. placebo.

RESULTS

The median survival ratio was significantly higher for O6-methylguanine-DNA methyltransferase (MGMT) methylated tumors versus unmethylated tumors following treatment with TMZ (median survival ratio, 3.6 vs. 1.5, respectively; p = 0.008) or TMZ/RT (5.7 vs. 2.3, respectively; p = 0.001) but not RT alone (1.7 vs. 1.6; p = 0.47). In an analysis of variance, MGMT methylation status and p53 mutation status were significantly associated with treatment response. When we analyzed the additional survival benefit conferred specifically by combined therapy, only a subset (5 of 11) of MGMT methylated tumors derived substantial additional benefit from combined therapy, while none of the MGMT unmethylated tumors did. Consistent with a true radiosensitizing effect of TMZ, sequential treatment in which RT (week 1) was followed by TMZ (week 2) proved significantly less effective than TMZ followed by RT or concurrent TMZ/RT (survival ratios of 4.0, 9.6 and 12.9, respectively; p < 0.0001).

CONCLUSIONS

Concurrent treatment with TMZ and RT provides significant survival benefit only in a subset of MGMT methylated tumors and provides superior antitumor activity relative to sequential administration of RT and TMZ.