Immunotherapy for Neuro-Oncology

Glioblastoma Vaccines as Promising Immune-Therapeutics: Challenges and Current Status

Glioblastoma (GBM) is the most common and aggressive malignant brain tumor. Standard treatments including surgical resection, radiotherapy, and chemotherapy, have failed to significantly improve the prognosis of glioblastoma patients. Currently, immunotherapeutic approaches based on vaccines, chimeric antigen-receptor T-cells, checkpoint inhibitors, and oncolytic virotherapy are showing promising results in clinical trials. The combination of different immunotherapeutic approaches is proving satisfactory and promising. In view of the challenges of immunotherapy and the resistance of glioblastomas, the treatment of these tumors requires further efforts. In this review, we explore the obstacles that potentially influence the efficacy of the response to immunotherapy and that should be taken into account in clinical trials. This article provides a comprehensive review of vaccine therapy for glioblastoma. In addition, we identify the main biomarkers, including isocitrate dehydrogenase, epidermal growth factor receptor, and telomerase reverse transcriptase, known as potential immunotherapeutic targets in glioblastoma, as well as the current status of clinical trials. This paper also lists proposed solutions to overcome the obstacles facing immunotherapy in glioblastomas.

Chimeric Antigen Receptor T Cells in Glioblastoma-Current Concepts and Promising Future

Glioblastoma (GBM) is a highly aggressive primary brain tumor that is largely refractory to treatment and, therefore, invariably relapses. GBM patients have a median overall survival of 15 months and, given this devastating prognosis, there is a high need for therapy improvement. One of the therapeutic approaches currently tested in GBM is chimeric antigen receptor (CAR)-T cell therapy. CAR-T cells are genetically altered T cells that are redirected to eliminate tumor cells in a highly specific manner. There are several challenges to CAR-T cell therapy in solid tumors such as GBM, including restricted trafficking and penetration of tumor tissue, a highly immunosuppressive tumor microenvironment (TME), as well as heterogeneous antigen expression and antigen loss. In addition, CAR-T cells have limitations concerning safety, toxicity, and the manufacturing process. To date, CAR-T cells directed against several target antigens in GBM including interleukin-13 receptor alpha 2 (IL-13Rα2), epidermal growth factor receptor variant III (EGFRvIII), human epidermal growth factor receptor 2 (HER2), and ephrin type-A receptor 2 (EphA2) have been tested in preclinical and clinical studies. These studies demonstrated that CAR-T cell therapy is a feasible option in GBM with at least transient responses and acceptable adverse effects. Further improvements in CAR-T cells regarding their efficacy, flexibility, and safety could render them a promising therapy option in GBM.

Predictors of Survival in Patients with Metastatic Brain Tumors: Experience from a Low-to-Middle-Income Country

Objective The interplay of static factors and their effect on metastatic brain tumor survival, especially in low-to-middle-income countries (LMICs), has been rarely studied. To audit our experience, and explore novel survival predictors, we performed a retrospective analysis of brain metastases (BM) patients at Shaukat Khanum Memorial Cancer Hospital (SKMCH), Pakistan.

Materials and Methods A retrospective review was conducted of consecutive patients who presented with BM between September 2014 and September 2019 at SKMCH. Patients with incomplete records were excluded.

Statistical Analysis SPSS (v.25 IBM, Armonk, New York, United States) was used to collect and analyze data via Cox-Regression and Kaplan–Meier curves.

Results One-hundred patients (mean age 45.89 years) with confirmed BM were studied. Breast cancer was the commonest primary tumor. Median overall survival (OS) was 6.7 months, while the median progression-free survival (PFS) was 6 months. Age (p = 0.001), gender (p = 0.002), Eastern Cooperative Oncology Group (p < 0.05), anatomical site (p = 0.002), herniation (p < 0.05), midline shift (p = 0.002), treatment strategies (p < 0.05), and postoperative complications (p < 0.05) significantly impacted OS, with significantly poor prognosis seen with extremes of age, male gender (hazard ratio [HR]: 2.0; 95% confidence interval [CI]: 1.3–3.1; p = 0.003), leptomeningeal lesions (HR: 5.7; 95% CI: 1.1–29.7; p = 0.037), and patients presenting with uncal herniation (HR: 3.5; 95% CI: 1.9–6.3; p < 0.05). Frontal lobe lesions had a significantly better OS (HR: 0.5; 95% CI: 0.2–1.0; p = 0.049) and PFS (HR: 0.08; 95% CI: 0.02–0.42; p = 0.003).

Conclusion BM has grim prognoses, with comparable survival indices between developed countries and LMICs. Early identification of both primary malignancy and metastatic lesions, followed by judicious management, is likely to significantly improve survival.

Advances in Immunotherapy for the Treatment of Adult Glioblastoma: Overcoming Chemical and Physical Barriers

Glioblastoma, or glioblastoma multiforme (GBM, WHO Grade IV), is a highly aggressive adult glioma. Despite extensive efforts to improve treatment, the current standard-of-care (SOC) regimen, which consists of maximal resection, radiotherapy, and temozolomide (TMZ), achieves only a 12-15 month survival. The clinical improvements achieved through immunotherapy in several extracranial solid tumors, including non-small-cell lung cancer, melanoma, and non-Hodgkin lymphoma, inspired investigations to pursue various immunotherapeutic interventions in adult glioblastoma patients. Despite some encouraging reports from preclinical and early-stage clinical trials, none of the tested agents have been convincing in Phase III clinical trials. One, but not the only, factor that is accountable for the slow progress is the blood-brain barrier, which prevents most antitumor drugs from reaching the target in appreciable amounts. Herein, we review the current state of immunotherapy in glioblastoma and discuss the significant challenges that prevent advancement. We also provide thoughts on steps that may be taken to remediate these challenges, including the application of ultrasound technologies.

Immunotherapeutic treatments for spinal and peripheral nerve tumors: a primer

OBJECTIVE

Spinal and peripheral nerve tumors are a heterogeneous group of neoplasms that can be associated with significant morbidity and mortality despite the current standard of care. Immunotherapy is an emerging therapeutic option to improve the prognoses of these tumors. Therefore, the authors sought to present an updated and unifying review on the use of immunotherapy in treating tumors of the spinal cord and peripheral nerves, including a discussion on mechanism of action, drug delivery, current treatment techniques, and preclinical and clinical studies.

METHODS

Current data in the literature regarding immunotherapy were collated and summarized. Targeted tumors included primary and secondary spinal tumors, as well as peripheral nerve tumors.

RESULTS

Four primary modalities of immunotherapy (CAR T cell, monoclonal antibody, viral, and cytokine) have been reported to target spine and peripheral nerve tumors. Of the primary spinal tumors, spinal cord astrocytomas had the most preclinical evidence supporting immunotherapy success with CAR T-cell therapy targeting the H3K27M mutation, whereas spinal schwannomas and ependymomas had the most evidence reported for monoclonal antibody therapy preclinically. Of the secondary spinal tumors, primary CNS lymphomas demonstrated some clinical response to immunotherapy, whereas multiple myeloma and bone tumor experiences with immunotherapy were largely limited to concept only. Within peripheral nerve tumors, the use of immunotherapy to treat neurofibromas in the setting of syndromes has been suggested in theory, and possible immunotherapeutic targets have been identified in malignant peripheral nerve tumors. To date, there have been 2 clinical trials involving spine tumors and 2 clinical trials involving peripheral nerve tumors that have reported results, all of which are promising but require validation.

CONCLUSIONS

Immunotherapy to treat spinal and peripheral nerve tumors has become an emerging area of research and interest. A large amount of preclinical data supporting the translation of this therapy into practice, aimed at ameliorating the poor prognoses of specific tumors, have been reported. Future clinical studies for translation will focus on the optimal therapy type and administration route to best target these tumors, which often preclude total surgical resection given their proximity to the neural and vascular elements of the spine.

Imaging of Neurologic Injury following Oncologic Therapy

Neurologic injury arises from treatment of central nervous system malignancies as result of direct toxic effects or indirect vascular, autoimmune, or infectious effects. Multimodality treatment may potentiate both therapeutic and toxic effects. Symptoms range from mild to severe and permanent. Injuries can be immediate or delayed. Many early complications are nonspecific. Other early and delayed neurologic injuries, such as posterior reversible encephalopathy syndrome, dural sinus thrombosis, infarctions, myelopathy, leukoencephalopathy, and hypophysitis, have unique imaging features. This article reviews treatment options for neurologic malignancies and common and uncommon neurologic injuries that can result from treatment, focusing on radiologic features.

Routine Neuroimaging in Patients with Stage IV Non-Small Cell Lung Cancer: A Single Center Experience

Background: There is a lack of consensus in current practice guidelines regarding routine neuroimaging in patients with stage IV non-small cell lung cancer (NSCLC) without neurologic symptoms, and there is a paucity of data on the impact of such imaging on overall survival (OS). Methods: This retrospective study included 257 patients with stage IV NSCLC without neurologic symptoms diagnosed between January 1, 2013 and December 31, 2016 at Institut universitaire de cardiologie et de pneumologie de Québec (IUCPQ). The primary objective of this study was to compare the evolution of patients with stage IV NSCLC who had baseline brain imaging versus with who did not. Secondary objectives were to determine the proportion of patients who underwent brain imaging in their initial investigation and the proportion of patients who developed metachronous central nervous system (CNS) metastasis. Results: CNS imaging, mainly with computed tomography (CT), was performed at diagnosis in 56% of patients, and the prevalence of synchronous CNS metastasis among these patients was 32%. There was no difference in median OS between patients who underwent initial CNS imaging and those who did not, but we did show a tendency for a higher cumulative incidence of metachronous CNS metastasis in patients without baseline imaging. These metachronous metastases were symptomatic and were more often not treated when compared to synchronous metastases. Conclusions: In this small, unicentric retrospective study, there was no benefit with routine neuroimaging in terms of median OS in stage IV NSCLC patients without neurologic symptoms.

Clinical and molecular immune characterization of ERBB2 in glioma

ERBB2 is a well-studied oncogene that promotes progression of multiple cancers, especially in breast cancer. However, the expression status of ERBB2, the values of ERBB2 on prognosis, and its molecular characterization in glioma have not been well examined. We explored the expression of ERBB2 and its clinical and molecular immune characterization in human glioma samples using the extracted genetic and clinical data from the Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA) databases. Immunohistochemistry (IHC) performed on the tissue microarray slide was used to validate the expression and clinical and prognostic values of ERBB2 in glioma. Higher ERBB2 expression was found in patients with higher grades gliomas than in patients with lower grades gliomas. Besides, patients with higher ERBB2 expression showed poor prognosis. The IHC and clinical data next validated the expression pattern and prognostic value of ERBB2 in glioma. Further analysis showed that there was a strong positive correlation between ERBB2 and common immune checkpoints as well as immune markers of various immune cells in both TCGA and CGGA databases, and the IHC data further validated the positive correlation between ERBB2 and PD-L1 expression. Besides, analysis of ERBB2-related immune genes and signatures showed the significant role of ERBB2 in mediating tumor immune response in glioma. To sum up, our findings summarize the expression pattern and clinical characteristics of ERBB2 in glioma, which may be useful for expanding our understanding of the critical role of ERBB2 in antitumor therapy in glioma.

Proton therapy reduces the likelihood of high-grade radiation-induced lymphopenia in glioblastoma patients: phase II randomized study of protons vs photons

BACKGROUND

We investigated differences in radiation-induced grade 3+ lymphopenia (G3+L), defined as an absolute lymphocyte count (ALC) nadir of <500 cells/µL, after proton therapy (PT) or X-ray (photon) therapy (XRT) for patients with glioblastoma (GBM).

METHODS

Patients enrolled in a randomized phase II trial received PT (n = 28) or XRT (n = 56) concomitantly with temozolomide. ALC was measured before, weekly during, and within 1 month after radiotherapy. Whole-brain mean dose (WBMD) and brain dose-volume indices were extracted from planned dose distributions. Univariate and multivariate logistic regression analyses were used to identify independent predictive variables. The resulting model was evaluated using receiver operating characteristic (ROC) curve analysis.

RESULTS

Rates of G3+L were lower in men (7/47 [15%]) versus women (19/37 [51%]) (P < 0.001), and for PT (4/28 [14%]) versus XRT (22/56 [39%]) (P = 0.024). G3+L was significantly associated with baseline ALC, WBMD, and brain volumes receiving 5‒40 Gy(relative biological effectiveness [RBE]) or higher (ie, V5 through V40). Stepwise multivariate logistic regression analysis identified being female (odds ratio [OR] 6.2, 95% confidence interval [CI]: 1.95‒22.4, P = 0.003), baseline ALC (OR 0.18, 95% CI: 0.05‒0.51, P = 0.003), and whole-brain V20 (OR 1.07, 95% CI: 1.03‒1.13, P = 0.002) as the strongest predictors. ROC analysis yielded an area under the curve of 0.86 (95% CI: 0.79-0.94) for the final G3+L prediction model.

CONCLUSIONS

Sex, baseline ALC, and whole-brain V20 were the strongest predictors of G3+L for patients with GBM treated with radiation and temozolomide. PT reduced brain volumes receiving low and intermediate doses and, consequently, reduced G3+L.

The promise of DNA damage response inhibitors for the treatment of glioblastoma

Glioblastoma (GBM), the most aggressive primary brain tumor, has a dismal prognosis. Despite our growing knowledge of genomic and epigenomic alterations in GBM, standard therapies and outcomes have not changed significantly in the past two decades. There is therefore an urgent unmet need to develop novel therapies for GBM. The inter- and intratumoral heterogeneity of GBM, inadequate drug concentrations in the tumor owing to the blood-brain barrier, redundant signaling pathways contributing to resistance to conventional therapies, and an immunosuppressive tumor microenvironment, have all hindered the development of novel therapies for GBM. Given the high frequency of DNA damage pathway alterations in GBM, researchers have focused their efforts on pharmacologically targeting key enzymes, including poly(ADP-ribose) polymerase (PARP), DNA-dependent protein kinase, ataxia telangiectasia-mutated, and ataxia telangiectasia and Rad3-related. The mainstays of GBM treatment, ionizing radiation and alkylating chemotherapy, generate DNA damage that is repaired through the upregulation and activation of DNA damage response (DDR) enzymes. Therefore, the use of PARP and other DDR inhibitors to render GBM cells more vulnerable to conventional treatments is an area of intense investigation. In this review, we highlight the growing body of data behind DDR inhibitors in GBM, with a focus on putative predictive biomarkers of response. We also discuss the challenges involved in the successful development of DDR inhibitors for GBM, including the intracranial location and predicted overlapping toxicities of DDR agents with current standards of care, and propose promising strategies to overcome these hurdles.