Childhood brain tumors: A review of strategies to translate CNS drug delivery to clinical trials

Brain tumors account for over 20% of childhood cancers and are the biggest cancer killer in children and young adults. Several initiatives over the past 40 years have tried to identify more effective drug treatments, but with very limited success. This is largely due to the bloodâ brain barrier, which restricts the entry of many drugs into the brain. In this review, we describe the main techniques that are being developed to enhance brain tumor drug delivery and explore the preclinical brain tumor models that are essential for translational development of these techniques. We also identify existing approved drugs that, if coupled with an efficient delivery method, could have potential as brain tumor treatments. Bringing this information together is part of a funded initiative to highlight drug delivery as a research strategy to overcome the current challenges for children diagnosed with brain tumors

Feasibility and safety of GliaSite brachytherapy in treatment of CNS tumors following neurosurgical resection

Purpose: To investigate feasibility and safety of GliaSite brachytherapy for treatment of central nervous system (CNS) tumors following neurosurgical resection. We report mature results of long-term follow-up, outcomes and toxicity. Materials and Methods: In the period from 2004 to 2007, 10 consecutive adult patients with recurrent, newly diagnosed, and metastatic brain malignancies underwent GliaSite brachytherapy following maximally safe neurosurgical resection. While 6/10 (60%) patients were treated for recurrence, having previously been treated with external beam radiotherapy (EBRT), 4/10 (40%) received radiotherapy (RT) for the first time. A median dose of 52.0 Gy (range, 45.0 - 60.0 Gy) was prescribed to 0.5 cm - 1.0 cm from the balloon surface. Radiation Therapy Oncology Group (RTOG) criteria were used to assess toxicities associated with this technique. Follow-up was assessed with MRI scans and was available on all enrolled patients. Results: Median follow-up was 38 months (range, 18 - 57 months). Mean size of GliaSite balloon was 3.4 cm (range, 2.0 - 4.0 cm). Median survival was 14.0 months for the entire cohort after the treatment. The 17.6 and 16.0 months average survival for newly diagnosed and recurrent high grade gliomas (HGG), respectively, translated into a three-month improvement in survival in patients with newly diagnosed HGG compared to historical controls (P = 0.033). There were no RTOG grades 3 or 4 acute or late toxicities. Follow-up magnetic resonance imaging (MRI) imaging did not identify radiation necrosis. Conclusions: Our data indicate that treatment with GliaSite brachytherapy is feasible, safe and renders acceptable local control, acute and long-term toxicities. We are embarking on testing larger numbers of patients with this treatment modality

Potential Savings of Harmonising Hospital and Community Formularies for Chronic Disease Medications Initiated in Hospital

Hospitals in Canada manage their formularies independently, yet many inpatients are discharged on medications which will be purchased through publicly-funded programs. We sought to determine how much public money could be saved on chronic medications if hospitals promoted the initiation of agents with the lowest outpatient formulary prices.We used administrative databases for the province of Ontario to identify patients initiated on a proton pump inhibitor (PPI), angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) following hospital admission from April 1(st) 2008-March 31(st) 2009. We assessed the cost to the Ontario Drug Benefit Program (ODB) over the year following initiation and determined the cost savings if prescriptions were substituted with the least expensive agent in each class.The cost for filling all PPI, ACE inhibitor and ARB prescriptions was $2.48 million,$968 thousand and $325 thousand respectively. Substituting the least expensive agent could have saved$1.16 million (47%) for PPIs, $162 thousand (17$14 thousand (4%) for ARBs over the year following discharge.In a setting where outpatient prescriptions are publicly funded, harmonising outpatient formularies with inpatient therapeutic substitution resulted in modest cost savings and may be one way to control rising pharmaceutical costs

Childhood Brain Tumors: A Review of Strategies to Translate CNS Drug Delivery to Clinical Trials

Brain and spinal tumors affect 1 in 1000 people by 25 years of age, and have diverse histological, biological, anatomical and dissemination characteristics. A mortality of 30–40% means the majority are cured, although two-thirds have life-long disability, linked to accumulated brain injury that is acquired prior to diagnosis, and after surgery or chemo-radiotherapy. Only four drugs have been licensed globally for brain tumors in 40 years and only one for children. Most new cancer drugs in clinical trials do not cross the blood–brain barrier (BBB). Techniques to enhance brain tumor drug delivery are explored in this review, and cover those that augment penetration of the BBB, and those that bypass the BBB. Developing appropriate delivery techniques could improve patient outcomes by ensuring efficacious drug exposure to tumors (including those that are drug-resistant), reducing systemic toxicities and targeting leptomeningeal metastases. Together, this drug delivery strategy seeks to enhance the efficacy of new drugs and enable re-evaluation of existing drugs that might have previously failed because of inadequate delivery. A literature review of repurposed drugs is reported, and a range of preclinical brain tumor models available for translational development are explored

Protein Phosphatase 2A Mediates Dormancy of Glioblastoma Multiforme-Derived Tumor Stem-Like Cells during Hypoxia

The hypoxic microenvironment of glioblastoma multiforme (GBM) is thought to increase resistance to cancer therapies. Recent evidence suggests that hypoxia induces protein phosphatase 2A (PP2A), a regulator of cell cycle and cell death. The effects of PP2A on GBM tumor cell proliferation and survival during hypoxic conditions have not been studied.Expression of PP2A subunits and HIF-α proteins was measured in 65 high-grade astrocytoma and 18 non-neoplastic surgical brain specimens by western blotting. PP2A activity was measured by an immunoprecipitation assay. For in vitro experiments, GBM-derived tumor stem cell-like cells (TSCs) were exposed to severe hypoxia produced by either CoCl₂ or 1% O₂. PP2A activity was inhibited either by okadaic acid or by shRNA depletion of the PP2A C subunit. Effects of PP2A activity on cell cycle progression and cell survival during hypoxic conditions were assessed using flow cytometry.In our patient cohort, PP2A activity was positively correlated with HIF-1∝ protein expression (P = 0.002). Patients with PP2A activity levels above 160 pMP had significantly worse survival compared to patients with levels below this threshold (P = 0.002). PP2A activity was an independent predictor of survival on multivariable analysis (P = 0.009). In our in vitro experiments, we confirmed that severe hypoxia induces PP2A activity in TSCs 6 hours after onset of exposure. PP2A activity mediated G1/S phase growth inhibition and reduced cellular ATP consumption in hypoxic TSCs. Conversely, inhibition of PP2A activity led to increased cell proliferation, exhaustion of intracellular ATP, and accelerated P53-independent cell death of hypoxic TSCs.Our results suggest that PP2A activity predicts poor survival in GBM. PP2A appears to reduce the metabolic demand of hypoxic TSCs and enhances tumor cell survival. Modulation of PP2A may be a potential target for cancer therapy

Hemorrhagic infarction secondary to cerebral venous thrombosis

Cerebral venous thrombosis (CVT) is an uncommon cause of hemorrhagic stroke. A 47-year old woman presented with acute-onset global aphasia and right hemiplegia. Head CT revealed a large left frontoparietal hematoma with significant mass effect. Emergency decompressive hemicraniectomy and hematoma evacuation were thus indicated. Intraoperatively, an occlusive thrombus was identified in the superior anastomotic vein of Trolard, confirming the diagnosis of CVT. While hemorrhagic CVT is not a rare entity, the diagnosis is not usually made intraoperatively. More interestingly, the authors provide intraoperative photographs of the occlusive thrombus in the vein of Trolard, overlying the area of hemorrhage, which they believe are unique and compelling clinical images. Keywords: Cerebral venous thrombosis, Dural sinus thrombosis, Intracerebral hemorrhage, Superior anastomotic vein of Trolard, Thrombophilia, Venous infarctio