Bassam Abdulkarim

Performance of Knowledge-Based Radiation Therapy Planning for the Glioblastoma Disease Site

PURPOSEnThe presence of multiple serial organs at risk (OARs) in close proximity to the tumor makes treatment planning for glioblastoma (GBM) complex and time consuming. The present study aimed to create a knowledge-based (KB) radiation therapy model for GBM patients using RapidPlan.nnnMETHODS AND MATERIALSnAn initial model was trained using 82 glioblastoma patients treated with 60xa0Gy in 30 fractions. Plans were created using either volumetric modulated arc therapy (VMAT) or intensity modulated radiation therapy (IMRT). To improve the goodness-of-fit of the model, an intermediate model was generated by using the dose-volume histograms (DVHs) of best spared OARs of the initial model. Using the intermediate model and manual refinement, all 82 cases were replanned, resulting in the final model. The final model was validated on an independent set of 45 patients with GBM, astrocytoma, oligodendroglioma, and meningioma.nnnRESULTSnThe plans created by the final model exhibited superior planning target volume (PTV) dose metrics compared with manual clinical plans: ΔD99%=-0.52xa0±xa00.20xa0Gy, and ΔD1%=0.80xa0±xa00.13xa0Gy (differences are computed as clinical-model). OAR maximum doses were statistically similar, with improved optic apparatus sparing (ΔDmax=2.78xa0±xa00.82xa0Gy). Stated improvements correspond to P<.05. The KB planning time is typically 7xa0minutes for IMRT and 13xa0minutes for VMAT, compared with a typical 4xa0hours for manual planning.nnnCONCLUSIONSnThe KB approach results in significant improvement in planning efficiency and in superior PTV coverage and better normal tissue sparing irrespective of tumor size and location within the brain.

Benefit of re-operation and salvage therapies for recurrent glioblastoma multiforme: results from a single institution

The optimal management of recurrent glioblastoma (GBM) has yet to be determined. We aim to assess the benefits of re-operation and salvage therapies (chemotherapy and/or re-irradiation) for recurrent GBM and to identify prognostic factors associated with better survival. All patients who underwent surgery for GBM between January 2005 and December 2012 followed by adjuvant radiotherapy, and who developed GBM recurrence on imaging were included in this retrospective study. Univariate and multivariate analysis was performed using Cox models in order to identify factors associated with overall survival (OS). One hundred and eighty patients treated to a dose of 60xa0Gy were diagnosed with recurrent GBM. At a median follow-up time of 6.2 months, the median survival (MS) from time of recurrence was 6.6xa0months. Sixty-nine patients underwent repeat surgery for recurrence based on imaging. To establish the benefits of repeat surgery and salvage therapies, 68 patients who underwent repeat surgery were matched to patients who did not based on extent of initial resection and presence of subventricular zone involvement at recurrence. MS for patients who underwent re-operation was 9.6 months, compared to 5.3 months for patients who did not have repeat surgery (pu2009<u20090.0001). Multivariate analysis in the matched pairs confirmed that repeat surgery with the addition of other salvage treatment can significantly affect patient outcome (HR 0.53). Re-operation with additional salvage therapies for recurrent GBM provides survival prolongation at the time of progression.

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

PURPOSEnWe performed a phase 2 trial of neoadjuvant temozolomide (TMZ), followed by hypofractionated accelerated radiation therapy (HART) with concurrent TMZ, and adjuvant TMZ in patients with newly diagnosed glioblastoma to determine whether neoadjuvant TMZ would safely improve outcomes in this group of patients prior to subsequent cytotoxic therapy.nnnMETHODS AND MATERIALSnAdult patients with newly diagnosed glioblastoma and a Karnofsky Performance Status >60 were eligible. Neoadjuvant TMZ administration started 2 to 3xa0weeks from surgery at a daily dose of 75xa0mg/m2 for 2xa0weeks prior to delivery of HART (60xa0Gy in 20 daily fractions) with concurrent and adjuvant TMZ. The primary endpoints were feasibility and toxicity. The secondary endpoints included overall survival (OS) and progression-free survival.nnnRESULTSnFifty patients were accrued. The median follow-up period was 44.0xa0months for patients at risk and 22.3xa0months for all 50 patients. Except for 1 patient in whom infection developed and another patient with progression during HART, all patients completed protocol therapy as planned. The median OS and progression-free survival were 22.3xa0months (95% confidence interval, 14.6-42.7xa0months) and 13.7xa0months (95% confidence interval, 8.0-33.3xa0months), respectively. The 4-year OS rates were 30.4% for the entire cohort and 53.3% and 14.0% for patients with methylated (n=21) and unmethylated (n=27) MGMT gene promoter tumors, respectively. One patient had grade 5 pancytopenia during HART, and another patient had transient grade 4 hepatotoxicity. A second surgical procedure was performed in 13 patients: 2 had intracranial infection, 3 had recurrences, 4 had recurrences and radiation-induced damage, and 4 had only radiation-induced damage.nnnCONCLUSIONSnThis novel approach of neoadjuvant TMZ is associated with an encouraging favorable long-term survival with acceptable toxicity. A future comparative trial of the efficacy of this regimen is warranted.

Divergent evolution of temozolomide resistance in glioblastoma stem cells is reflected in extracellular vesicles and coupled with radiosensitization

BackgroundnGlioblastoma (GBM) is almost invariably fatal due to failure of standard therapy. The relapse of GBM following surgery, radiation, and systemic temozolomide (TMZ) is attributed to the ability of glioma stem cells (GSCs) to survive, evolve, and repopulate the tumor mass, events on which therapy exerts a poorly understood influence.nnnMethodsnHere we explore the molecular and cellular evolution of TMZ resistance as it emerges in vivo (xenograft models) in a series of human GSCs with either proneural (PN) or mesenchymal (MES) molecular characteristics.nnnResultsnWe observed that the initial response of GSC-initiated intracranial xenografts to TMZ is eventually replaced by refractory growth pattern. Individual tumors derived from the same isogenic GSC line expressed divergent and complex profiles of TMZ resistance markers, with a minor representation of O6-methylguanine DNA methyltransferase (MGMT) upregulation. In several independent TMZ-resistant tumors originating from MES GSCs we observed a consistent diminution of mesenchymal features, which persisted in cell culture and correlated with increased expression of Nestin, decline in transglutaminase 2 and sensitivity to radiation. The corresponding mRNA expression profiles reflective of TMZ resistance and stem cell phenotype were recapitulated in the transcriptome of exosome-like extracellular vesicles (EVs) released by GSCs into the culture medium.nnnConclusionsnIntrinsic changes in the tumor-initiating cell compartment may include loss of subtype characteristics and reciprocal alterations in sensitivity to chemo- and radiation therapy. These observations suggest that exploiting therapy-induced changes in the GSC phenotype and alternating cycles of therapy may be explored to improve GBM outcomes.

Prediction of survival with multi-scale radiomic analysis in glioblastoma patients

AbstractWe propose a multiscale texture features based on Laplacian-of Gaussian (LoG) filter to predict progression free (PFS) and overall survival (OS) in patients newly diagnosed with glioblastoma (GBM). Experiments use the extracted features derived from 40 patients of GBM with T1-weighted imaging (T1-WI) and Fluid-attenuated inversion recovery (FLAIR) images that were segmented manually into areas of active tumor, necrosis, and edema. Multiscale texture features were extracted locally from each of these areas of interest using a LoG filter and the relation between features to OS and PFS was investigated using univariate (i.e., Spearman’s rank correlation coefficient, log-rank test and Kaplan-Meier estimator) and multivariate analyses (i.e., Random Forest classifier). Three and seven features were statistically correlated with PFS and OS, respectively, with absolute correlation values between 0.32 and 0.36 and pu2009<u20090.05. Three features derived from active tumor regions only were associated with OS (pu2009<u20090.05) with hazard ratios (HR) of 2.9, 3, and 3.24, respectively. Combined features showed an AUC value of 85.37 and 85.54% for predicting the PFS and OS of GBM patients, respectively, using the random forest (RF) classifier. We presented a multiscale texture features to characterize the GBM regions and predict he PFS and OS. The efficiency achievable suggests that this technique can be developed into a GBM MR analysis system suitable for clinical use after a thorough validation involving more patients.n Graphical abstractScheme of the proposed model for characterizing the heterogeneity of GBM regions and predicting the overall survival and progression free survival of GBM patients. (1) Acquisition of pretreatment MRI images; (2) Affine registration of T1-WI image with its corresponding FLAIR images, and GBM subtype (phenotypes) labelling; (3) Extraction of nine texture features from the three texture scales fine, medium, and coarse derived from each of GBM regions; (4) Comparing heterogeneity between GBM regions by ANOVA test; Survival analysis using Univariate (Spearman rank correlation between features and survival (i.e., PFS and OS) based on each of the GBM regions, Kaplan-Meier estimator and log-rank test to predict the PFS and OS of patient groups that grouped based on median of feature), and multivariate (random forest model) for predicting the PFS and OS of patients groups that grouped based on median of PFS and OS.

Abstract A66: Ablative radiotherapy increases invasion potential in EGFR-wildtype non-small cell lung cancer cells compared to fractionated radiotherapy.

Introduction: Non-small cell lung cancer (NSCLC) accounts for over 80% of all lung cancer cases. Nearly 70% of lung cancer patients will undergo radiotherapy (RT). Recent trends in RT have shown an increase in the use of ablative radiotherapy (ART) in inoperable small tumors with response rates of 80-90% in NSCLC patients. However, despite the high rate of local control, early clinical data shows no advantage in survival due to distant metastasis after ART compared to conventional fractionated radiotherapy (FRT). In addition, patient selection for ART is independent of the status of the epidermal growth factor receptor (EGFR) which has been shown to play a role in radiation response. We investigated the effect of ART compared to FRT on cell invasion, proliferation, senescence and clonogenic survival of NSCLC cell lines harboring wild type and mutated EGFR. Methods: The cell lines used were A549, H1975 and HCC827. Cell irradiation was performed using a Faxitron X-Ray machine. Radiation doses of 8Gy and12Gy were delivered in fractionated or single sessions. The effect of radiation on cells was investigated using the clonogenic assay, MTT proliferation assay, matrigel invasion assay and senescence-associated beta-galactosidase. Results: ART significantly suppressed the proliferative and clonogenic potential of wild-type EGFR A549 cells compared to FRT. In addition, a significant increase in the number of senescent as well as large, polynucleated cells was observed in the ART-treated group compared to the FRT-treated group. Analysis of the invasive potential of the cells revealed a 2-fold increase in invasion 5 days after exposure to ART of 12Gy compared to control. The FRT group showed a 1.4-fold increase in invasion compared to control. Contrary to A549 cells, EGFR-mutated NSCLC HCC827 and H1975 cells, showed no significant difference after exposure to ART compared to FRT. In addition, both ART and FRT-treated groups showed a similar increase in the number of senescent, large and polynucleated cells. A significant reduction in the number of invading cells after exposure to either FRT or ART was observed compared to the control. Conclusion: ART significantly reduces cell proliferation and clonogenic survival compared to FRT in wild-type EGFR A549 cells. This differential response between the type of treatment (ART vs FRT) was not seen in NSCLC cell lines harboring EGFR mutations. In contrast to reduced cell proliferation, there was a significant increase in the invasive capacity of cells after ART compared to FRT in A549 cells only. These results can have significant consequences in the selection and treatment of NSCLC patients for ART. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A66. Citation Format: Ayman J. Oweida, Jack Xu, Siham Sabri, Bassam Abdulkarim. Ablative radiotherapy increases invasion potential in EGFR-wildtype non-small cell lung cancer cells compared to fractionated radiotherapy. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A66.

Prognostic factors for progression in atypical meningioma

In patients with postoperative residual atypical meningiomas, by using volumetric instead of linear measurements in follow-up imaging studies, the authors detected disease progression earlier. By using this approach, treatment for recurrent disease can be instituted promptly with potentially better tumor control and less toxicity due to smaller volume of residual disease.

Abstract 2740: Identification of new binding partners of the DNA repair protein MGMT using a proteomic discovery-based approach in glioblastoma

Background: Glioblastoma multiforme (GBM) is characterized by aberrant angiogenesis and widespread invasion through the brain parenchyma. The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) has been extensively characterized for its role in resistance to alkylating agents used in treatment of GBM. Our team discovered an inverse relationship between expression of MGMT and GBM angiogenesis and invasion. To gain new insights into how MGMT affects angiogenesis and invasion, we used a proteomic-based approach integrated with bioinformatics analysis to identify potential MGMT-binding partners (BPs) for the first time in GBM. Methods: We used T98G, a human GBM cell line with constitutive expression of MGMT and performed direct immunoprecipitation (IP) of endogenous MGMT using an anti-MGMT antibody or the isotype control. Following elution of the antibody, proteins were resolved by SDS-PAGE, stained, excised from the gel then subjected to trypsin digestion and identified by liquid chromatography-tandem mass spectrometry using the LTQ-Orbitrap Elite mass analyzer. The resulting tryptic peptides were purified and identified by LC-tandem mass spectrometry (MS/MS). The resultant MS/MS spectra were searched against a proteome database for peptide matching and protein identification. Proteins identified with high confidence (Scaffold software) were used to construct the biological network of MGMT-BPs in GBM using the Build Network tool provided by MetaCore. Results: We identified a total of 186 MGMT-BPs, which were not identified in the elution from the isotype control. Using gene ontology (GO) database, we determined the function and biological role of identified proteins (mitochondrial metabolism, DNA repair and replication, ubiquitin pathway, transcription regulators, RNA post-transcriptional processing, transcriptional splicing, protein biosynthesis and trafficking, cellular metabolism, cell cycle and division, response to stress and cell death, cell migration and invasion). The list of new BPs was uploaded to MetaCore and the most relevant biological process was enriched based on public GO databases. Among the top proteins identified with a very high confidence, we found newly identified MGMT-BPs, which may underlie the role of MGMT in angiogenesis and invasion, namely the splicing factor heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1), known for its role in the packaging of pre-mRNA into hnRNP particles and alternative splicing of angiogenic factors (VEGF-A and the fibroblast growth factor 2) and annexin A2. Knockdown of annexin A2 decreased invasion, angiogenesis and proliferation in vivo. Conclusion: Our study provides new mechanistic insights into how MGMT affects angiogenesis and invasion in GBM, which may ultimately lead to the identification of new therapeutic targets to improve the poor outcome of this devastating disease. Note: This abstract was not presented at the meeting. Citation Format: Siham Sabri, Yaoxian Xu, Bassam Abdulkarim. Identification of new binding partners of the DNA repair protein MGMT using a proteomic discovery-based approach in glioblastoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2740. doi:10.1158/1538-7445.AM2014-2740