Safety and efficacy of a multicenter study using intraarterial chemotherapy in conjunction with osmotic opening of the blood-brain barrier for the treatment of patients with malignant brain tumors

Initial response to glucocorticoids

BACKGROUND

Known prognostic variables in patients with primary central nervous system lymphomas (PCNSL) include age, Karnofsky performance status, involvement of deep regions of the brain, intensity of blood-brain barrier disruption, and treatment with radiation and chemotherapy. PCNSL often responds transiently to glucocorticoids administered to control neurologic symptoms before radiation or chemotherapy. This retrospective chart review was designed to estimate the prognostic significance of a clinical or radiologic response to initial glucocorticoid therapy.

METHODS

By using data from The Johns Hopkins Cancer Registry from January 1980 to June 2001, a total of 76 human immunodeficiency virus (HIV)-negative adults with newly diagnosed PCNSL were identified. Nineteen patients with uninformative medical records were excluded from the study.

RESULTS

The median survival of the remaining 57 patients was 11.8 months. The median survival for the 48 patients who had clinical response to initial steroid therapy was 17.9 months, and for nonresponders, it was 5.5 months (P = 0.05). The 16 patients with documented radiologic response had a median survival of 117.0 months compared with 5.5 months for nonresponders (P = 0.001). After adjusting for known prognostic factors (age and treatment), significant reduction in risk of death was noted in patients who had either clinical (hazard ratio [HR] = 0.40; 95% confidence interval [CI], 0.16-0.99}) or radiologic response (HR = 0.14; 95% CI, 0.04-0.46) to glucocorticoids given before radiation or chemotherapy.

CONCLUSION

This analysis suggests that initial response to treatment with glucocorticoids may be an important prognostic factor in patients with PCNSL.

New Delivery Approaches for Pediatric Brain Tumors

For many types of childhood brain tumors, including malignant gliomas, disease progression at the primary site is the predominant mode of treatment failure. Accordingly, interest has been directed during the last decade on exploring strategies to enhance the delivery of therapeutically active agents into the tumor microenvironment. Two approaches that have been the focus of considerable attention in the treatment of adult malignant brain tumors include interstitial administration of chemotherapeutic agents using time-release polymers and convection-enhanced delivery of immunotoxin conjugates targeted to receptors overexpressed in brain tumors relative to normal brain cells. Although it remains to be determined whether these approaches will lead to meaningful improvements in disease control and long-term prognosis in children with brain tumors, the encouraging results from studies in adults support the rationale for further exploring these strategies in the pediatric setting.

Osmotic blood–brain barrier disruption chemotherapy for diffuse pontine gliomas

The prognosis for patients with diffuse pontine gliomas (DPG) remains poor. New aggressive innovative treatments are necessary to treat this disease. From 1984 to 1998, eight patients (4M/4F), median age 11 years, with DPG were treated with monthly osmotic blood-brain barrier disruption (BBBD) chemotherapy using intraarterial carboplatin or methotrexate and intravenous cytoxan and etoposide. Patients presented for a median duration of 6 weeks with increased intracranial pressure, long tract signs, diplopia, ataxia, and nausea/vomiting. DPG was demonstrated on magnetic resonance (MR) imaging in seven patients and on CT in one. Two patients had biopsies that showed an astrocytoma and an anaplastic astrocytoma. Three tumors enhanced on MR imaging after contrast administration. Three patients had radiation therapy before BBBD chemotherapy and four afterwards. Two patients had chemotherapy (tamoxifen, topotecan) before BBBD chemotherapy and two afterwards. In general, patients were evaluated with MR imaging every 3 months to monitor for a response to treatment. The median number of chemotherapy cycles that were administered by BBBD was 10, mean 10. Three patients also received one, two, or three cycles of intraarterial chemotherapy without BBBD. One patient that was started on carboplatin was converted to methotrexate, and five that were started on the methotrexate protocol were later converted over to carboplatin. One patient received monthly methotrexate followed by 14 days of procarbazine and one patient started on methotrexate was switched to navelbine. MR imaging demonstrated two partial responses, five patients with stable disease, and one with disease progression. The median time to tumor progression was 15 months with the range from <1 to 40 months. The median survival from the time of diagnosis was 27 months, ranging from 7 to 80 months. The median survival time from the first BBBD or intraarterial treatment was 16.5 months, ranging from 5 to 69 months. One patient was lost to follow-up with an unknown date of death. Although the sample size is small, the TTP and survival times are longer than those previously reported in other DPG series. In addition, the ability to demonstrate stable disease or partial responses in DPG on MR imaging argues for the therapeutic benefit of BBBD chemotherapy. The enhanced delivery of chemotherapy afforded by osmotic BBBD supports the further examination of this treatment modality for patients with DPG.

Primary central nervous system lymphoma

Primary central nervous system lymphoma is a stage 1E non-Hodgkin's lymphoma confined to the nervous system. It is seen in immunocompetent and immunodeficient populations, the latter group associated with the Epstein-Barr virus. Primary central nervous system lymphoma can affect the brain, leptomeninges, spinal cord or eyes. The institution of high-dose methotrexate-based regimens and whole-brain radiation therapy has significantly increased survival, but neurotoxicity is high in patients over 60 years of age. Despite these advances, 50% of patients initially treated will relapse. Recent investigations include the use of rituximab (immunotherapy) and stem-cell transplantation, as well as regimens without whole-brain radiation therapy in the elderly. The optimal treatment regimen is yet to been determined.

Intra-arterial chemotherapy of primary brain tumors

Intra-arterial (IA) chemotherapy is a form of regional delivery to brain tumors, designed to enhance the intra-tumoral concentrations of a given drug, in comparison with the intravenous route. Drugs that are likely to benefit from IA delivery have a rapid systemic clearance and include carmustine and other nitrosoureas, cisplatin, carboplatin, etoposide, and methotrexate. Clinical studies have demonstrated activity of IA chemotherapy approaches for low- and high-grade gliomas, and for cerebral lymphomas. However, a survival benefit for IA drug delivery, in comparison with intravenous administration, has not been proven in phase III trials. The technique is limited by the potential for significant vascular and neurologic toxicity, including visual loss, stroke, and leukoencephalopathy. More recent studies suggest that toxicity can be reduced by the use of carboplatin- and methotrexate-based regimens. Further clinical studies will be needed to determine the appropriate role for IA chemotherapy in the treatment of primary brain tumors.

MRI-guided targeted blood-brain barrier disruption with focused ultrasound: histological findings in rabbits

Focused ultrasound offers a method to disrupt the blood-brain barrier (BBB) noninvasively and reversibly at targeted locations. The purpose of this study was to test the safety of this method by searching for ischemia and apoptosis in areas with BBB disruption induced by pulsed ultrasound in the presence of preformed gas bubbles and by looking for delayed effects up to one month after sonication. Pulsed ultrasound exposures (sonications) were performed in the brains of 24 rabbits under monitoring by magnetic resonance imaging (MRI) (ultrasound: frequency = 1.63 MHz, burst length = 100 ms, PRF = 1 Hz, duration = 20 s, pressure amplitude 0.7 to 1.0 MPa). Before sonication, an ultrasound contrast agent (Optison, GE Healthcare, Milwaukee, WI, USA) was injected IV. BBB disruption was confirmed with contrast-enhanced MR images. Whole brain histologic examination was performed using haematoxylin and eosin staining for general histology, vanadium acid fuchsin-toluidine blue staining for ischemic neurons and TUNEL staining for apoptosis. The main effects observed were tiny regions of extravasated red blood cells scattered around the sonicated locations, indicating affected capillaries. Despite these vasculature effects, only a few cells in some of the sonicated areas showed evidence for apoptosis or ischemia. No ischemic or apoptotic regions were detected that would indicate a compromised blood supply was induced by the sonications. No delayed effects were observed either by MRI or histology up to 4 wk after sonication. Ultrasound-induced BBB disruption is possible without inducing substantial vascular damage that would result in ischemic or apoptotic death to neurons. These findings indicate that this method is safe for targeted drug delivery, at least when compared with the currently available invasive methods.

Reducing cerebral blood flow increases the duration of electroencephalographic silence by intracarotid thiopental

The effects of IV anesthetics are enhanced by increased cerebral blood flow (CBF) because of a greater delivery of drugs to the brain. In contrast, mathematical simulations suggest that a decrease in CBF, by increasing regional drug uptake and decreasing drug washout, enhances the efficacy of intraarterial drugs. We hypothesized that administrating intracarotid anesthetics during cerebral hypoperfusion will significantly prolong the duration of electroencephalographic (EEG) silence. We tested our hypothesis on New Zealand White rabbits. In the first group of 7 animals, we observed that decreasing CBF by approximately 70% attenuated, but did not abolish, EEG activity. Subsequently, 9 animals received 3 intracarotid injections of 3 mg of thiopental (thiopental-1, thiopental + hypoperfusion, and thiopental-2). The first and third injections were made under physiological conditions. The second drug injection was made during cerebral hypoperfusion. Compared with injection of thiopental-1 and -2, thiopental + hypoperfusion resulted in a profound increase in EEG silence (from 45 +/- 5 and 67 +/- 27 s, to 206 +/- 46 s, respectively, n = 9, P < 0.0001). The EEG recovery profile was similar during all three thiopental challenges. The study suggests that modulation of CBF is an important tool for enhancing intraarterial drug delivery to the brain.

Evaluation of vascular supply with angio-computed tomography during intra-arterial chemotherapy for brain tumors

We report the utility of a combined angiography and computed tomography (angio-CT) system in assessing drug distribution to the tumor during intra-arterial chemotherapy for metastatic brain tumors in a 65-year-old man. Although digital subtraction angiography did not clearly show tumor perfusion in two cerebellar tumors, angio-CT provided definite tumor perfusion in the complicated vascular territory, and anticancer agents were infused based on its findings. To our knowledge, however, this application for intra-arterial chemotherapy of brain tumors has not been previously described.

Central nervous system metastases in breast cancer patients administered trastuzumab

Amplification or over-expression of the HER2/neu receptor is present in 20-30% of invasive breast cancers and in 60% of intraductal breast carcinomas. Patients with HER2/neu gene aberrations have more aggressive disease, frequent disease recurrence and a shorter survival. Trastuzumab (herceptin) is a monoclonal antibody selectively directed against the HER2/neu receptor. The addition of trastuzumab to chemotherapy in HER2/neu-positive advanced breast cancer patients has increased complete and partial response rates, and prolonged time to progression and overall survival. However, a relatively common failure site in patients administered trastuzumab is the central nervous system (CNS). CNS metastases in these patients seem to develop despite responses achieved in extracerebral sites. This pattern of failure has mainly been attributed to the lack of trastuzumab penetration to the CNS owing to the high molecular weight (145 kDa) of this molecule. Additionally, increased risk of CNS relapse may be associated with improved systemic control of extracerebral metastases and prolonged survival without brain protection (a sanctuary site). Finally, it was postulated that HER2/neu over-expression and/or amplification might predispose to brain metastases. The aim of this article is to discuss the pathophysiology of this phenomenon and its clinical implications.

Hyperosmotic mannitol induces Src kinase-dependent phosphorylation of beta-catenin in cerebral endothelial cells

Mannitol, which is a cell-impermeable and nontoxic polyalcohol, has been shown to be a useful tool for reversible opening of the blood-brain barrier (BBB). Despite successful clinical trials, the molecular mechanism of the mannitol-induced changes in cerebral endothelial cells (CECs) are poorly understood. For our experiments, we used CECs in culture, which were treated with different, clinically relevant concentrations of mannitol. We found that mannitol induced a rapid, concentration-dependent, and reversible tyrosine phosphorylation of a broad range of proteins between 50 and 190 kDa. One of the targets of tyrosine phosphorylation turned out to be the adherens junction protein beta-catenin. Phosphorylation of beta-catenin on tyrosine residues caused its subcellular redistribution and its dissociation from cadherin and alpha-catenin as shown by coimmunoprecipitation studies. All these effects could be inhibited by the Src kinase inhibitor PP-1 but not by the Erk inhibitor U0126, the Rho kinase inhibitor Y27632, or the calcium channel blocker verapamil. Because beta-catenin is a key component of the junctional complex, its Src-mediated phpsphorylation may play an important role in the mannitol induced reversible opening of the BBB.

Enhanced Prospects for Drug Delivery and Brain Targeting by the Choroid Plexus–CSF Route

The choroid plexus (CP), i.e., the blood-cerebrospinal fluid barrier (BCSFB) interface, is an epithelial boundary exploitable for drug delivery to brain. Agents transported from blood to lateral ventricles are convected by CSF volume transmission (bulk flow) to many periventricular targets. These include the caudate, hippocampus, specialized circumventricular organs, hypothalamus, and the downstream pia-glia and arachnoid membranes. The CSF circulatory system normally provides micronutrients, neurotrophins, hormones, neuropeptides, and growth factors extensively to neuronal networks. Therefore, drugs directed to CSF can modulate a variety of endocrine, immunologic, and behavioral phenomema; and can help to restore brain interstitial and cellular homeostasis disrupted by disease and trauma. This review integrates information from animal models that demonstrates marked physiologic effects of substances introduced into the ventricular system. It also recapitulates how pharmacologic agents administered into the CSF system prevent disease or enhance the brain's ability to recover from chemical and physical insults. In regard to drug distribution in the CNS, the BCSFB interaction with the blood-brain barrier is discussed. With a view toward translational CSF pharmacotherapy, there are several promising innovations in progress: bone marrow cell infusions, CP encapsulation and transplants, neural stem cell augmentation, phage display of peptide ligands for CP epithelium, CSF gene transfer, regulation of leukocyte and cytokine trafficking at the BCSFB, and the purification of neurotoxic CSF in degenerative states. The progressively increasing pharmacological significance of the CP-CSF nexus is analyzed in light of treating AIDS, multiple sclerosis, stroke, hydrocephalus, and Alzheimer's disease.

Local and reversible blood-brain barrier disruption by noninvasive focused ultrasound at frequencies suitable for trans-skull sonications

The purpose of this study was to test the hypothesis that burst ultrasound in the presence of an ultrasound contrast agent can disrupt the blood-brain barrier (BBB) with acoustic parameters suitable for completely noninvasive exposure through the skull. The 10-ms exposures were targeted in the brains of 22 rabbits with a frequency of 690 kHz, a repetition frequency of 1 Hz, and peak rarefactional pressure amplitudes up to 3.1 MPa. The total exposure (sonication) time was 20 s. Prior to each sonication, a bolus of ultrasound contrast agent was injected intravenously. Contrast-enhanced MR images were obtained after the sonications to detect localized BBB disruption via local enhancement in the brain. Brain sections were stained with H&E, TUNEL, and vanadium acid fuchsin (VAF)-toluidine blue staining. In addition, horseradish peroxidase (HRP) was injected into four rabbits prior to sonications and transmission electron microscopy was performed. The MRI contrast enhancement demonstrated BBB disruption at pressure amplitudes starting at 0.4 MPa with approximately 50%; at 0.8 MPa, 90%; and at 1.4 MPa, 100% of the sonicated locations showed enhancement. The histology findings following 4 h survival indicated that brain tissue necrosis was induced in approximately 70-80% of the sonicated locations at a pressure amplitude level of 2.3 MPa or higher. At lower pressure amplitudes, however, small areas of erythrocyte extravasation were seen. The electron microscopy findings demonstrated HRP passage through vessel walls via both transendothelial and paraendothelial routes. These results demonstrate that completely noninvasive focal disruption of the BBB is possible.

Dynamics of CNS Barriers: Evolution, Differentiation, and Modulation

(1) Three main barrier layers at the interface between blood and tissue protect the central nervous system (CNS): the endothelium of brain capillaries, and the epithelia of the choroid plexus (CP) and the arachnoid. The classical work on these barriers in situ until the 1970s laid the foundations for modern understanding. Techniques for brain endothelial cell isolation and culture pioneered by Ferenc Joó in the 1970s opened up new fields of examination, enabling study of mechanisms at the cellular and molecular level. (2) Astrocytic glial cells are closely associated with the brain endothelial barrier. During evolution the barrier appears to have shifted from the glial to the endothelial layer, in parallel with the increasing importance of the microvasculature and its regulation. Vestiges of the barrier potential of glia remain in the modern mammalian CNS. (3) Evolutionary evidence suggests that the advantage derived from ionic homeostasis around central synapses was the major selective pressure leading to refinement of CNS barrier systems. This is one element of the modern 'multitasking' barrier function. (4) While epithelia are constitutively able to form barriers at appropriate interfaces, the 'default' condition for endothelia is more leaky; inductive influences from associated cells especially astrocytes are important in generating the full blood-brain barrier (BBB) phenotype in brain capillaries. The underlying mechanisms are being elucidated at the molecular and genomics level. (5) The barrier layers of the nervous system can be modulated by a number of receptor-mediated processes, involving several signal transduction pathways, both calcium dependent and independent. Some agents acting as 'inducers' in the long term can act as 'modulators' in the short-term, with some overlap of signaling pathways. Modulating agents may be derived both from the blood and from cells associated with cerebral vessels. Less is known about the modulation of the CP. (6) The challenge for the next era of CNS barrier studies will be to apply new knowledge from proteomics and genomics to understanding the in vivo condition in physiology and pathology.

Intracarotid delivery of oncolytic HSV vector G47Δ to metastatic breast cancer in the brain

Delivery of viral vectors to tumors in the brain is a challenge, especially via systemic administration, which is key to targeting the invasive margins of malignant glioma and the multiple foci of metastatic disease. Like for other cancer therapeutics, the blood-brain barrier or even the blood-tumor barrier significantly limits delivery and efficacy. Blood-brain barrier disruption (BBBD) is one strategy for transiting the cerebrovasculature. G47Delta is a third-generation oncolytic replication-competent herpes simplex virus (HSV) vector, containing deletions of the gamma34.5 and alpha47 genes and an inactivating LacZ insertion in UL39 (ICP6). Intracarotid artery delivery of G47Delta after BBBD with 25% mannitol significantly extended the life of nude mice bearing intracerebral human MDA-MB-435 breast tumors, whereas, G47Delta injection contralateral to the tumor, in the absence of mannitol or mannitol alone had no effect on survival. G47Delta replication was extensive after BBBD, as visualized by X-gal staining. Staining of peripheral organs, lung and liver, was minimal and not altered by BBBD. This is the first demonstration of intracarotid arterial delivery of oncolytic HSV vectors and antitumor efficacy in a mouse model and opens the door to the use of mouse syngenic tumor models and transgenic/knockout animals.

Enhanced chemotherapy delivery by intraarterial infusion and blood-brain barrier disruption in malignant brain tumors

BACKGROUND

The treatment of malignant brain tumors is hampered by the presence of the blood-brain barrier, which limits chemotherapy penetration to the central nervous system (CNS). In recent years, different strategies have been designed to circumvent this physiologic barrier. The osmotic blood-brain barrier disruption (BBBD) procedure is one such strategy, and has been studied extensively in preclinical and clinical studies. The authors detail their experience so far with the procedure in the context of an open Phase II study in the treatment of malignant brain tumors.

METHODS

Patients with histologically proven malignant gliomas, primitive neuroectodermal tumors, primary CNS lymphomas, and metastatic disease to the brain were eligible. Patients enrolled were treated every 4 weeks (1 cycle) for < or = 12 cycles. A methotrexate-based regimen was offered to patients with lymphomas, whereas a carboplatin-based regimen was offered to patients with all other histologies. Before intraarterial chemotherapy infusion, patients were submitted to an osmotic BBBD procedure.

RESULTS

Seventy-two patients were included in the current report. The overall median survival times (MST) from treatment initiation for glioblastoma multiforme (GBM), anaplastic oligodendrogliomas, primary CNS lymphomas, and metastases were, respectively, 9.1, 13.9, not reached, and 9.9 months, whereas time to disease progression was 4.1, 9.2, 12.3, and 3.3 months. The MST from diagnosis was 32.2 months for GBM.

CONCLUSIONS

These encouraging results prompted the authors to further refine their knowledge of the potential contribution of this procedure in the treatment of brain tumors. These authors designed a randomized Phase III study for patients with GBM that is now open.

The effects of magnesium sulfate on blood-brain barrier disruption caused by intracarotid injection of hyperosmolar mannitol in rats

The study was performed to evaluate whether magnesium sulfate could alter the degree of disruption of the blood-brain barrier (BBB) caused by hyperosmotic mannitol. Wistar adult female rats were infused with 25% mannitol into the left internal carotid artery. Each animal received intraperitoneally a 300 mg/kg loading dose of magnesium sulfate, dissolved in 0.9% saline, followed by a further 100 mg/kg dose. In the other group, intracarotid infusion of magnesium sulfate was performed at a dose of 150 mg/kg 10 min before mannitol administration. Evans blue (EB) dye was used as a marker of BBB disruption. The measured serum glucose and magnesium levels increased after mannitol and/or magnesium administration when compared with their initial values before treatment (P < 0.01). Water content of the left hemisphere was significantly increased by hyperosmotic mannitol (P < 0.01). The increased water content in the mannitol-perfused hemisphere was significantly decreased by magnesium treatment (P < 0.05). The content of EB dye in the mannitol-perfused hemisphere markedly increased when compared with the right hemisphere of the same brain (P < 0.01). The EB dye content in the mannitol-perfused hemisphere following both intraperitoneal and intraarterial administration of magnesium decreased when compared with mannitol alone (P < 0.01). We conclude that although magnesium sulfate administration by both intracarotid arterial and intraperitoneal routes attenuates BBB disruption caused by hyperosmolar mannitol, particularly intraperitoneal route of magnesium sulfate administration may provide a useful strategy to limit the transient osmotic opening of the BBB.

Anaplastic astrocytoma: diagnosis, prognosis, and management

The designation of a tumor as anaplastic astrocytoma (AA) reflects a distinct histologic classification of malignant glioma characterized by an abundance of pleomorphic astrocytes with evidence of mitosis. Although these tumors are malignant, they have a better prognosis and a higher likelihood of response to treatment than glioblastoma. Despite advances in brain tumor imaging, making an accurate diagnosis requires the evaluation of tumor tissue and is essential for treatment planning. Currently, most patients undergo maximal surgical debulking of tumor followed by external beam radiation, often with subsequent adjuvant chemotherapy. However, despite the use of these treatment modalities, most tumors recur within a few years and these recurrent tumors are more refractory to subsequent therapies. This review examines the diagnosis, prognosis, and treatment of AAs. Ongoing clinical research investigations are also summarized, reflecting advances in our knowledge of the molecular pathogenesis of these tumors and providing hope for significant improvements in patient outcomes.

Treatment of primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is a rare neoplasm that has captured popular attention because of its rising incidence and marked chemosensitivity. It is a non-Hodgkins B-cell lymphoma (NHL) that appears confined to the central nervous system (CNS) at presentation but may be multifocal within the brain or involve the leptomeninges or eyes at diagnosis. Like systemic lymphoma, it is highly sensitive to corticosteroids, and administration of steroids should be withheld until the diagnosis has been confirmed histologically. Currently, the initial treatment of choice incorporates high-dose methotrexate (HD-MTX) either as a single agent or in combination with other systemic chemotherapies. Whole-brain radiotherapy (WBRT) can be a highly effective treatment modality when combined with MTX, but the combination causes an unacceptably high incidence of severe permanent neurotoxicity, particularly in patients over age 60. Therefore, chemotherapy alone is the initial treatment of choice in older patients. This approach is also being explored in younger patients, but it is possible that deferring radiotherapy may compromise disease control. Consequently, the role of radiotherapy remains to be clarified in newly diagnosed younger patients with PCNSL.

Why study transport of peptides and proteins at the neurovascular interface

The blood-brain barrier (BBB) is an immense neurovascular interface. In neurodegenerative, ischemic, and traumatic disorders of the central nervous system (CNS), the BBB may hinder the delivery of many therapeutic peptides and proteins to the brain and spinal cord. Fortunately, the mistaken dogma that peptides and proteins do not cross the BBB has been corrected during the past two decades by the accumulating evidence that peptides and proteins in the periphery exert potent effects in the CNS. Not only can peptides and proteins serve as carriers for selective therapeutic agents, but they themselves may directly cross the BBB after delivery into the bloodstream. Their passage may be mediated by simple diffusion or specific transport, both of which can be affected by interactions in the blood compartment (outside the BBB) and within the endothelial cells (at the BBB level). Although the majority of current delivery strategies focuses on modification of the molecule to be delivered, understanding the mechanisms of transport will eventually facilitate regulation of the BBB directly. We review the different aspects of interactions and discuss recent advances in the cell biology of peptide/protein transport across the BBB. Better understanding of the nature and regulation of the transport systems at the BBB will provide a new direction to enhance the interactions of peripheral peptides and proteins with the CNS.

Blood-brain barrier opened by stimulation of the parasympathetic sphenopalatine ganglion: a new method for macromolecule delivery to the brain

OBJECT

Drug delivery across the blood-brain barrier remains a significant challenge. Based on earlier findings, the authors hypothesized that parasympathetic innervation of the brain vasculature could be used to augment drug delivery to the brain.

METHODS

Using a craniotomy-cerebrospinal fluid superfusate paradigm in rats with an intravenous injection of tracer the authors demonstrated that stimulation of the postganglionic parasympathetic fibers of the sphenopalatine ganglion (SPG) increased the concentration of fluorescein isothiocyanate-dextran (4-250 kD) in the superfusate by two- to sixfold. A histological examination indicated the presence of dextran in the parenchyma. In another experiment the amount of Evans blue dye in the brain following SPG activation was similarly significantly elevated. The chemotherapeutic agents anti-HER2 monoclonal antibody and etoposide were also delivered to the brain and reached therapeutic concentrations. Brain homeostasis was not disturbed by this procedure; a measurement of nicotinamide adenine dinucleotide reduction did not show a decrease in the tissue metabolic state and brain water content did not increase significantly.

CONCLUSIONS

Sphenopalatine ganglion activation demonstrates a promising potential for clinical use in the delivery of small and large molecules to the brain.

[The blood-brain barrier should not be underestimated in neuro-oncology]

INTRODUCTION

Limited therapeutic success in the treatment of CNS neoplasia with chemotherapy is generally attributed to two factors: natural or acquired resistance to chemotherapy expressed by tumor cells, and delivery impediment related to the blood-brain barrier.

STATE OF ART

The anatomic and physiological properties of the normal blood-brain barrier prevent passage of ionized water-soluble compounds with a molecular weight greater than 500 Daltons. Although complex, the blood-brain barrier basically functions at the level of the tight junctions of the cerebral vascular endothelial cells. Different approaches have been advocated to improve delivery across the blood-brain barrier. One such approach, transient osmotic permeabilization of the blood-brain barrier, is an invasive procedure offering the potential of global delivery. This strategy involves cerebral intravascular infusion of a hypertonic solution to produce, in a given cerebral distribution (carotid or vertebral), producing a transient increase in blood-brain barrier permeability. Two parameters are paramount in the ability to mediate a hyperosmolar modification of the barrier: the osmolality of the solution, and the infusion time. The procedure has been found to produce a marked increase (10- to 100-fold) in brain and cerebrospinal fluid concentrations of methotrexate and of other markers.

PERSPECTIVES

Pre-clinical studies are underway to assess the use of this procedure to improve delivery of different molecules, including standard chemotherapy, monoclonal antibodies and gene therapy molecules. This approach has been standardized for clinical use. It has been extensively used in patients. Using a standard protocol of osmotic blood-brain barrier disruption to enhance chemotherapy delivery with three different chemotherapy regimens, more than 3000 procedures have been performed in more than 300 patients across the blood-brain barrier distribution consortium, an entity which includes six university centers coordinated by the Oregon Health Sciences University. The procedure has been found to be safe, with very limited toxicity. As part of this consortium, the Sherbrooke University center has been offering this treatment modality since November 1999. We have performed more than 500 procedures in 122 patients with various histologies (malignant gliomas, primary central nervous system lymphoma and metastasis) with low toxicity.

CONCLUSIONS

In our view, the median survival rate of 138 weeks obtained with glioblastoma multiforme patients is promising; further research to improve these results is needed.

Mannitol opening of the blood-brain barrier: regional variation in the permeability of sucrose, but not 86Rb+ or albumin

Clinically, infusion of hyperosmolar solutions is used to enhance chemotherapeutic drug penetration of the blood-brain barrier (BBB) in patients with malignant brain tumors or metastases. We examined the effect of hyperosmolar BBB disruption on brain permeability of three compounds, 86Rb+, a marker for K+ permeability and transport, [14C]sucrose and Evans blue albumin, using a rat in situ perfusion model. 86Rb+ and [14C]sucrose had increased permeability 20 min after BBB disruption with 1.6 M mannitol. There was no change in Evans blue albumin permeability. Only [14C]sucrose showed regional variation in permeability after mannitol-induced BBB disruption, with the cortex and midbrain having higher sucrose permeability then either the cerebellum or brainstem. These data suggest that the clinical efficacy of hyperosmolar disruption therapy in conjunction with chemotherapeutic agents, of a similar molecular weight to sucrose, may be affected by the location of the tumor within the brain.

Modulation of the blood–brain barrier in oncology: therapeutic opportunities for the treatment of brain tumours?

Systemically administered chemotherapy is not very effective in the treatment of primary or metastatic brain tumours. An important reason for this low efficacy is insufficient drug delivery to the tumour site due to the presence of the blood-brain barrier (BBB). In this review, we give an overview of strategies that were tested to bypass the BBB or to increase its permeability for anticancer drugs. Local drug administration through intracerebral implants offers only little benefit to patients with brain tumours, probably due to the limited diffusion of the drugs in brain tissue. Temporary disruption of the BBB can be achieved with intracarotid infusions of hypertonic mannitol. This method has been used with some success; however, toxic side effects and the high complexity of the surgical procedure limit its usefulness. More recently, the use of the bradykinin agonist cereport was shown to be useful in preclinical studies, but unfortunately clinical studies did not show improved efficacy. Since P-glycoprotein in the BBB restricts the brain entry of many anticancer drugs, inhibition of this drug transporter may be an option for improved drug delivery to brain tumours. Pre-clinical studies have shown the feasibility to enhance the penetration of paclitaxel into the brain by co-administration with a potent P-glycoprotein inhibitor and further clinical research is warranted.

Prospects for gene therapy in the fragile X syndrome

"If politics is the art of the possible, research is the art of the soluble. Both are immensely practical-minded affairs." P. B. Medawar.Gene therapy is unarguably the definitive way to treat, and possibly cure, genetic diseases. A straightforward concept in theory, in practice it has proven difficult to realize, even when directed to easily accessed somatic cell systems. Gene therapy for diseases in which the central nervous system (CNS) is the target organ presents even greater challenges and diverse vectors and brain delivery approaches are under investigation. We argue that in the case of the fragile X syndrome the approach most likely to have a chance of being effective should consist of a small, diffusible vector derived from the adeno-associated virus, carrying an FMR1 cDNA comprising the 5' promoter region and the 3' untranslated region of the gene, delivered to the entire brain by osmotic blood-brain barrier disruption. The approach can be tested in Fmr1 knockout mice, although changes in their neurobehavioral abnormalities may be difficult to evaluate. A defect in the expression of GABA(A) receptors in these mice-if shown to be a direct consequence of the Fmr1 defect-promises to be a more readily assessable marker of restored FMRp function on gene transfer.

Current advances in the diagnosis and management of intracranial germ cell tumors

Central nervous system (CNS) germ cell tumors (GCT) account for less than 5% of primary brain tumors in children and young adults, but they continue to attract much attention. Over the past decade, two advances have led to re-evaluation of what constitutes conventional therapy for CNS GCT. For pure germinomas, the challenge remains the determination of the optimal field and dose of irradiation and whether or not the use of chemotherapy can lead to a reduced dose or elimination of irradiation altogether without compromising disease control or survival. For non-germinomatous germ cell tumors, an improvement in the current dismal prognosis is imperative.

A vibrator prevents streaming during close-arterial infusion into the kidney

Close-arterial infusion of test substances allows one to study the responses of a selected vascular bed without inducing confounding systemic effects. Unfortunately, laminar flow patterns within the artery cause streaming of the injected factor, so that distribution within the target organ is not homogeneous. We describe a reliable method of overcoming these problems. Specifically, we attach a vibrator (i-Vibe egg) to the syringe containing the test substance. We showed that, without vibration, infusion of a solution of Evans blue (0.5% wt/vol) results in uneven distribution of the dye in the kidney. Vibration of the syringe during infusion allows for uniform coloration of the kidney surface. There is also functional improvement of drug distribution during vibration. Renal blood flow was measured during intrarenal infusion of phenylephrine (150 μl, 0.05–0.5 μg). Vibration caused a significant leftward shift in the dose-response curve, i.e., the phenylephrine-induced reduction in renal blood flow was enhanced by vibration. This cheap, simple method for ensuring adequate mixing of intra-arterially infused substances will facilitate not only the study of renal function in the rat but also infusion of test and therapeutic substances into other organs.

Quantitative analysis of hyperosmotic and hypothermic blood-brain barrier opening

Hyperosmotic opening of the blood-brain barrier (BBB) by mannitol is being used to enhance drug transport in human brains. Recently, cooling of the solution has been reported to have potential to open the BBB. However, the mechanism in barrier opening and closure remains elusive. We studied the rapid changes in cerebrovascular permeability after hyperosmotic and hypothermic BBB opening in rats, and then demonstrated that the Na+/Ca++ exchange blocker (KB-R7943) prolongs opening. BBB opening was attained by using intra-arterial infusion of hyperosmotic mannitol (1.6 M) and 1.1 M mannitol (which is less hyperosmotic than commonly used mannitol) at 4 degrees in Sprague-Dawley (SD) rats. To measure the changes in cerebrovascular permeability, perfusate-containing [14C]-sucrose was infused intra-arterially at different time points following hyperosmotic and hypothermic stress. Cerebrovascular permeability was then measured with the in situ brain perfusion technique. 1.6 M Mannitol produced opening of the BBB but the duration of the opening was less than 30 minutes. Use of 1.1 M Mannitol at 4 degrees indicated the same results. We then investigated the effect of a Na/Ca ion exchange blocker (KB-R7943) in both hyperosmotic and hypothermic BBB opening. KB-R7943 extended BBB opening up to 30 min without affecting the peak level of BBB permeability at 5 minutes. Our findings represent important experimental information regarding pharmacological manipulation of BBB opening. The possibility of prolonging the transient opening of the BBB has major clinical implications.

Bone Marrow Chemoprotection without Compromise of Chemotherapy Efficacy in a Rat Brain Tumor Model

Thiol chemoprotective agents can reduce chemotherapy side effects, but clinical use is limited due to concerns of impaired chemotherapeutic efficacy. We evaluated whether an optimized bone marrow chemoprotection regimen impaired the efficacy of enhanced chemotherapy against rat brain tumors. Nude rats with intracerebral human lung carcinoma xenografts were treated with carboplatin, melphalan, and etoposide phosphate delivered intra-arterially with osmotic blood-brain barrier disruption (n = 8/group). Thiol chemoprotection was N-acetyl-L-cysteine (1000 mg/kg) 60 min before chemotherapy and/or sodium thiosulfate (8 g/m(2)) 4 and 8 h after chemotherapy, when the blood-brain barrier is reestablished. Blood counts were obtained before treatment on day 3 and at sacrifice on day 9. N-acetylcysteine serum clearance half-life was 9 to 11 min. Pretreatment with N-acetylcysteine combined with delayed administration of sodium thiosulfate protected against toxicity toward total white cells, granulocytes, and platelets (P = 0.0016). Enhanced chemotherapy reduced intracerebral tumor volume to 4.3 +/- 1.0 mm(3) compared with 29.1 +/- 4.1 mm(3) in untreated animals (P < 0.0001). Tumor volume was 3.7 +/- 0.6 mm(3) in rats that received N-acetylcysteine before and sodium thiosulfate after chemotherapy. The data indicate the efficacy of enhanced chemotherapy for rat brain tumors was not affected by thiol chemoprotection that provided excellent protection for hematological toxicity. Negative interactions of thiols with antitumor efficacy were avoided by temporal and spatial separation of chemoprotectants and chemotherapy.

BR96-DOX immunoconjugate targeting of chemotherapy in brain tumor models

An immunoconjugate of doxorubicin (adriamycin) and a tumor-specific monoclonal antibody, BR96-DOX (now SGN-15) targets chemotherapy to cells that express the LewisY antigen. This immunoconjugate is internalized into lysosomes in antigen-expressing cells, with release of free doxorubicin after hydrolysis of the acid-labile linker. We review our studies using BR96-DOX in a human small-cell lung carcinoma intracerebral xenograft model in nude rats. We have found that the immunoconjugate is effective against intracerebral tumors when delivery is enhanced with osmotic disruption of the blood-brain barrier (BBB). Enhanced delivery of BR96-DOX with BBB opening can work together with radiotherapy to increase antitumor efficacy, which is maximally effective if immunoconjugate is administered prior to radiotherapy. In heterogeneous brain tumors, enhanced delivery of BR96-DOX significantly reduced tumor volumes, but local release of doxorubicin by targeting antigen expressing cells shows modest cytotoxicity against adjacent non-expressor cells. Although BR96-DOX is not effective against glioma cells tested, it does provide a model for drug-immunoconjugate therapy of gliomas. Our studies in a rat brain tumor model point out the importance of optimized delivery, antigenic heterogeneity, and bystander effect for brain tumor therapy. We review additional studies of drug-mAb immunoconjugates pertinent to the treatment of gliomas.

MRI investigation of the threshold for thermally induced blood-brain barrier disruption and brain tissue damage in the rabbit brain

The ability of MRI-derived thermometry to predict thermally induced tissue changes in the brain was tested, and the thermal thresholds for blood-brain barrier (BBB) disruption and brain tissue damage were estimated. In addition, the ability of standard MRI to detect threshold-level effects was confirmed. These safety thresholds are being investigated to provide guidelines for clinical thermal ablation studies in the brain. MRI-monitored focused ultrasound heating was delivered to 63 locations in 26 rabbits. Tissue changes were detected in T(2)-weighted imaging and T(1)-weighted imaging (with and without contrast) and with light microscopy. The probability for tissue damage as a function of the accumulated thermal dose, the peak temperature achieved, the applied acoustic energy, and the peak acoustic power was estimated with probit regression. The discriminative abilities of these parameters were compared using the areas under the receiver operator characteristic (ROC) curves. In MRI, BBB disruption was observed in contrast-enhanced T(1)-weighted imaging shortly after the ultrasound exposures, sometimes accompanied by changes in T(2)-weighted imaging. Two days later, changes in T(2)-weighted imaging were observed, sometimes accompanied by changes in T(1)-weighted imaging. In histology, tissue damage was seen at every location where MRI changes were observed, ranging from small (diameter <1.0 mm) areas of tissue necrosis to severe vascular damage and associated hemorrhagic infarct. In one location, small (diameter: 0.8 mm) damage was not detected in MRI. The thermal dose and peak temperature thresholds were between 12.3-40.1 equivalent min at 43 degrees C and 48.0-50.8 degrees C, respectively, and values of 17.5 equivalent min at 43 degrees C and 48.4 degrees C were estimated to result in tissue damage with 50% probability. Thermal dose and peak temperature were significantly better predictors than the applied acoustic energy and peak acoustic power (P < 0.01). BBB disruption was always accompanied by tissue damage. The temperature information was better than the applied acoustic power or energy for predicting the damage than the ultrasound parameters. MRI was sensitive in detecting threshold-level damage.

Intensive methotrexate and cytarabine followed by high-dose chemotherapy with autologous stem-cell rescue in patients with newly diagnosed primary CNS lymphoma: an intent-to-treat analysis

PURPOSE

To assess the safety and efficacy of intensive methotrexate-based chemotherapy followed by high-dose chemotherapy (HDT) with autologous stem-cell rescue in patients with newly diagnosed primary CNS lymphoma (PCNSL).

PATIENTS AND METHODS

Twenty-eight patients received induction chemotherapy using high-dose systemic methotrexate (3.5 g/m2) and cytarabine (3 g/m2 daily for 2 days). Fourteen patients with chemosensitive disease evident on neuroimaging then received high-dose therapy using carmustine, etoposide, cytarabine, and melphalan with autologous stem-cell rescue.

RESULTS

The objective response rate to the induction-phase chemotherapy was 57%, and median overall survival is not yet assessable, with a median follow-up time of 28 months. The overall median event-free survival time is 5.6 months for all patients and 9.3 months for 14 patients who underwent transplantation. Six of these 14 patients (43%) remained disease-free at last follow-up. Treatment was well tolerated; there was one transplantation-related death. Prospective neuropsychologic evaluations have revealed no evidence of treatment-related neurotoxicity.

CONCLUSION

This treatment approach is feasible in patients with newly diagnosed PCNSL without evidence of significant related neurotoxicity. Although the transplantation results are similar to those achieved in patients with aggressive or poor-prognosis systemic lymphoma, the low response rate to induction chemotherapy and the significant number of patients who experienced relapse soon after HDT suggest that more aggressive induction chemotherapy may be warranted.

Selective opening of the blood-tumor barrier by a nitric oxide donor and long-term survival in rats with C6 gliomas

OBJECT

The response of brain tumors to systemic chemotherapy is limited by the blood-tumor barrier (BTB). Nitric oxide (NO) has been implicated in the regulation of vascular permeability and blood flow. The authors evaluated the effects of exogenous NO, which was released from a short-acting NO donor (Proli/NO), and those of NO metabolites on the capillary permeability of tumors and normal brain tissue by using quantitative autoradiography in a C6 glioma model in rats.

METHODS

The Proli/NO was infused at a wide dose range (10(-2) to 10(-12) M) either intravenously or into the internal carotid artery (ICA) and demonstrated substantial tumor-selective increases in blood-brain barrier (BBB) permeability in response to various-sized tracers ([14C]aminoisobutyric acid, [14C]sucrose, [14C]dextran). Internal carotid artery or intravenous administration of sodium nitrite had a comparable effect on BTB permeability. The NO effect on microvascular permeability could be obtained without causing hemodynamic side effects. The effect of NO on the efficacy of carboplatin chemotherapy was investigated in intracerebral C6 gliomas. Simultaneous intravenous infusions of Proli/NO (10(-6) M) and carboplatin (20 mg/kg) led to long-term survival in 40% of rats harboring intracerebral C6 gliomas compared with control animals receiving ICA or intravenous infusions of carboplatin, Proli/NO, or vehicle alone. No residual tumor was demonstrated on histological or magnetic resonance imaging studies performed in rats treated with Proli/NO and carboplatin, and no toxicity was observed.

CONCLUSIONS

This new approach demonstrated the in vivo efficacy and safety of NO and nitrite in enhancing the delivery of systemically delivered radiolabeled tracers and carboplatin into rat gliomas. The NO-induced tumor-selective BBB disruption and intravenous carboplatin chemotherapy may be more efficacious than current chemotherapy strategies against brain tumors.

Alkylglycerol opening of the blood-brain barrier to small and large fluorescence markers in normal and C6 glioma-bearing rats and isolated rat brain capillaries

1. The blood-brain barrier (BBB) represents the major impediment to successful delivery of therapeutic agents to target tissue within the central nervous system. Intracarotid alkylglycerols have been shown to increase the transfer of chemotherapeutics across the BBB. 2. We investigated the spatial distribution of intracarotid fluorescein sodium and intravenous lissamine-rhodamine B200 (RB 200)-albumin in the brain of normal and C6 glioma-bearing rats after intracarotid co-administration of 1-O-pentylglycerol (200 mm). To elucidate the mechanisms involved in the alkylglycerol-mediated BBB opening, intraluminal accumulation of fluorescein isothiocyanate (FITC)-dextran 40,000 was studied in freshly isolated rat brain capillaries using confocal microscopy during incubation with different alkylglycerols. Furthermore, 1-O-pentylglycerol-induced increase in delivery of methotrexate (MTX) to the brain was evaluated in nude mice. 3. Microscopic evaluation showed a marked 1-O-pentylglycerol-induced extravasation of fluorescein and RB 200-albumin in the ipsilateral normal brain. In glioma-bearing rats, increased tissue fluorescence was found in both tumor tissue and brain surrounding tumor. Confocal microscopy revealed a time- and concentration-dependent accumulation of FITC-dextran 40,000 within the lumina of isolated rat brain capillaries during incubation with 1-O-pentylglycerol and 2-O-hexyldiglycerol, indicating enhanced paracellular transfer via tight junctions. Intracarotid co-administration of MTX and 1-O-pentylglycerol (200 mm) in nude mice resulted in a significant increase in MTX concentrations in the ipsilateral brain as compared to controls without 1-O-pentylglycerol (P<0.005). 4. In conclusion, 1-O-pentylglycerol increases delivery of small and large compounds to normal brain and brain tumors and this effect is mediated at least in part by enhanced permeability of tight junctions.

The expression and functional characterization of ABCG2 in brain endothelial cells and vessels

Delivery of drugs to the brain is impeded by the activity of efflux pumps expressed by endothelial cells of brain vasculature. The ATP binding cassette (ABC) transporters, among which ABCB1/MDR1 P-glycoprotein and ABCC1/multidrug resistance-associated protein 1 are expressed in brain endothelial cells, participate in drug efflux properties of the blood-brain barrier (BBB). Searches of the EST (expressed sequence tags) database with the conserved ABC domain, conducted to identify other ABC transporters expressed in the BBB, recovered 15 ABC transporter sequences expressed in human brain cDNA libraries. One of these sequences, identical to ABCG2, was highly expressed in cultured human cerebromicrovascular endothelial cells and human brain tissue at both mRNA and protein levels. Overexpression of human ABCG2 in immortalized rat brain endothelial cells resulted in enhanced polarized abluminal to luminal transport of various substrates tested in the in vitro BBB model. Brain vessels extracted from tissue sections of nonmalignant human brain and glioblastoma tumors by laser capture microdissection microscopy and analyzed by real-time polymerase chain reaction showed higher expression of ABCG2 relative to ABCB1/MDR1 and ABCC1/MRP1. ABCG2 was up-regulated in both glioblastoma vessels and parenchymal tissue. These studies suggest a role for brain endothelial ABCG2 transporter in modulating drug delivery to the brain and in conferring drug resistance to glioblastomas.

Summary statement on primary central nervous system lymphomas from the Eighth International Conference on Malignant Lymphoma, Lugano, Switzerland, June 12 to 15, 2002

Under the sponsorship of the International Extranodal Lymphoma Study Group, a Multidisciplinary Workshop on primary CNS lymphoma (PCNSL) with over 50 participants from Europe, North America, Israel, and Australia was held as part of the Eighth International Conference on Malignant Lymphoma in Lugano, Switzerland (June 12 to 15, 2002). The main purposes of the Workshop were to exchange the latest scientific information, to analyze methodologic issues in the design of clinical trials, to reach a consensus on treatment recommendations and prognostic factors, to discuss clinical and molecular targets for future studies, and to establish an international collaborative group to conduct laboratory and clinical investigations in PCNSL. This article summarizes the contents of the Workshop, analyzes the current knowledge on the most relevant biologic and clinical issues in PCNSL, and focuses on fundamental challenges to be addressed in future studies.

Intracarotid administration of short-chain alkylglycerols for increased delivery of methotrexate to the rat brain

1 The intracarotid administration of alkylglycerols has been reported previously by us to be a novel strategy for increased delivery of various chemotherapeutic drugs to the normal brain and brain tumors in rats. 2 Effectiveness and structure-activity relations of the most promising pentyl- and hexylglycerol derivatives have been elucidated in vivo by analyzing the transfer of methotrexate (MTX) across the blood-brain barrier (BBB) in normal rats. The effects were compared with BBB disruption using hypertonic mannitol or intracarotid infusion of bradykinin. Furthermore, toxicity of the alkylglycerols has been studied in long-term experiments. 3 Apart from 1-O-pentyldiglycerol, all alkylglycerols induced a concentration-dependent increase in MTX delivery to the brain varying from 1.1 to more than 300-fold compared to intra-arterial MTX alone. Enhanced barrier permeability rapidly approached baseline values within 5 and 120 min at the latest. Chemical structure, concentration, time schedule of injections and combination of different alkylglycerols were identified as instruments suited to regulate the MTX accumulation within a wide range. Mannitol 1.4 M resulted in very high MTX levels in the brain as observed using the highest concentrations of alkylglycerols. Intracarotid infusion of bradykinin had only a minor effect on the BBB. Using 1-O-pentylglycerol or 2-O-hexyldiglycerol, both cell culture experiments and long-term in vivo analyses including clinical, laboratory and histopathological evaluations revealed no signs of toxicity. 4 In summary, intracarotid short-chain alkylglycerols constitute a very effective and low toxic strategy for transient opening of the BBB to overcome the limited access of cytotoxic drugs to the brain.

Intra-arterial Chemotherapy for Malignant Tumors of Head and Neck Region Using Three Types of Modified Injection Method

SUMMARY

Relatively higher infusion rate in the intra-arterial chemotherapy (IA chemotherapy) could induce the higher concentration and the more sufficient distribution of chemotherapeutic agents on tumors. To get the relatively higher infusion rate in IA chemotherapy, we used three types of injection method: high-flow injection, high-dose injection with detoxification and flowcontrolled injection method for the treatment of malignant brain tumors, skull base tumors and head and neck tumors. Between January 1997 and October 2001, twenty-seven patients (mean age 61 y.o.) with supratentorial glioblastoma (4 cases), supratentorial anaplastic astrocytoma (1), CNS lymphoma (2), matastatic skull base tumors (3), and neck tumors (15 squamous cell carcinoma, 1 malignant melanoma and 1 neuroblastoma) received our three types of IA chemotherapy. Sixty- five consecutive procedures were performed. Conventional radiation therapy and/or surgical removal were performed in some of these patients. The median follow-up period was 10 months ranging 2 to 56 months. Fifteen (55.6%) and 6 (22.2%) of 27 patients achieved complete response (CR) and partial response (PR) respectively after initial treatment [CR+PR: 21 (77.8%)]. All responded patients showed clinical improvement. The response rate declined to 55.6% at the end of follow-up period. Eighteen patients are still alive and 15 of them show no evidence of local recurrence. The median post treatment survival was 12 months. There was no serious complication except transient nausea in 4 of 27 (14%) patients, vertigo and granulocytopenia in 1 each (3%) of 27 patients. Our modified IA chemotherapy has provided favorable clinical and radiological results without technical difficulties and serious complications.

Current status and future of relapsed primary central nervous system lymphoma (PCNSL)

The treatment of primary central nervous system lymphoma (PCNSL) has centered around high-dose methotrexate and radiotherapy (RT). Methotrexate administered intra-arterially (IA) with blood-brain barrier disruption (BBBD) and without RT, has been a highly effective treatment with a 5 year survival of 42% without cognitive loss. The purpose of this analysis is to determine responses for patients with relapsed PCNSL treated with second line IA carboplatin-based chemotherapy with BBBD. Between February 1991 and April 2000, 37 relapsed PCNSL patients, most who failed front line therapy with methotrexate based chemotherapy, were treated at Oregon Health & Science University (OHSU) and Hadassah Hebrew University Hospital (HHUH) with IA carboplatin-based chemotherapy with BBBD. Nine patients had prior RT. The mean age was 57.5 years, and all but 1 patient were treated within 8 months after relapse. The median time for survival from first IA carboplatin/BBBD treatment was 6.8 months;however, 7 out of 37 patients survived > or = 27 months. Nine patients had radiographic complete response (CR), 4 patients had radiographic partial response (PR), 12 had stable disease (SD), 10 had progressive disease (PD), and 2 were non-evaluable. The median time to failure for patients with CR and PR was 9.1 months. One long-term survivor is alive at 91.0 months from first carboplatin/BBBD treatment. In conclusion, we show that relapsed PCNSL has shown sensitivity to second line IA carboplatin-based chemotherapy with BBBD. We have developed a new protocol using i.v. rituximab prior to BBBD with IA carboplatin, i.v. cyclophosphamide and i.v. etoposide phosphate. The long-term program goal is to consolidate dose-intensive chemotherapy with monoclonal antibody directed radiation. Because patients with recurrent PCNSL commonly continue to relapse even after obtaining a complete response to enhanced chemotherapy treatment, patients w ho complete or fail the above carboplatin/BBBD treatment regimen will be offered consolidation with radioimmunotherapy using zevalin (Ibritumomab tiuxetan), IDEC-2B8 conjugated with yttrium-90 (90Y).

Zonula occludens toxin increases the permeability of molecular weight markers and chemotherapeutic agents across the bovine brain microvessel endothelial cells

The purpose of this study was to examine the ability of Zonula occludens toxin (Zot) to reversibly open tight junctions in bovine brain microvessel endothelial cells (BBMECs) to enhance drug delivery via the paracellular pathway. Transport across BBMEC monolayers was examined for molecular weight markers and chemotherapeutic agents ([(14)C]sucrose, [(14)C]inulin, [(3)H]propranolol, [(3)H]doxorubicin, and [(14)C]paclitaxel) with Zot (0.0-4.0 microg/mL). TEER of monolayers was measured to assess effect and reversibility of Zot. Cell viability of BBMEC in the presence of Zot was assessed by trypan blue exclusion staining. Apparent permeability (P(app)), enhancement ratio (R), and percent increase in transport determined were statistically compared by ANOVA. A significant increase (p < 0.05) in P(app) was observed for the transport of [(14)C]sucrose, [(14)C]inulin, [(3)H]doxorubicin, and [(14)C]paclitaxel at a 4.0 microg/mL concentration of Zot. A significant concentration-dependent decrease in TEER was observed on treatment with Zot with rapid reversal to baseline after removal. Zot (4 micro/ml) was found to be nontoxic to the BBMECs after 2 hours incubation. In conclusion, Zot increased paracellular transport across the BBMEC in a reversible, concentration-dependent manner. Modulation of paracellular transport with Zot may be used to increase the brain permeability of potent central nervous system-active drugs, including anticancer agents.

Targets for pharmacological intervention of endothelial hyperpermeability and barrier function

Many diseases share the common feature of vascular leakage, and endothelial barrier dysfunction is often the underlying cause. The subsequent stages of endothelial barrier dysfunction contribute to endothelial hyperpermeability. Vasoactive agents induce loss of junctional integrity, a process that involves actin-myosin interaction. Subsequently, the interaction of leukocytes amplifies leakage by the leukocyte-derived mediators. The processes mainly occur at the postcapillary venules. The whole microvascular bed, including the capillaries, becomes involved in vascular leakage by the induction of angiogenesis. Plasma leakage results from gaps between endothelial cells as well as by the induction of transcellular transport pathways. Several mechanisms can improve endothelial barrier function, depending on the tissue affected and the cause of hyperpermeability. They include blockade of specific receptors and elevation of cyclic AMP (cAMP) by agents such as beta(2)-adrenergic agents. However, current therapies based on these principles often fail. Recent research has identified several new promising targets for pharmacological therapy. Endogenous compounds were also found with barrier-improving characteristics. Important insights were obtained in the different pathways involved in barrier dysfunction. Such insights regard the regulation of endothelial contraction and endothelial junction integrity: inhibitors of RhoA activation and Rho kinase represent a potentially valuable group of agents with endothelial hyperpermeability reducing properties, and strategies to target vascular endothelial growth factor (VEGF)-mediated edema are under current investigation. In clinical practice, not only tools to improve an impaired endothelial barrier function are necessary. Sometimes, a controlled, temporal, and local increase in permeability can also be desired, for example, with the aim to enhance drug delivery. Therefore, vessel leakiness is also being exploited to enable tissue access of liposomes, viral vectors, and other therapeutic agents that do not readily cross healthy endothelium. This review discusses strategies for targeting signaling molecules in therapies for diseases involving altered endothelial permeability.

Chemotherapy for the treatment of metastatic brain tumors

Metastatic brain tumors are the most common complication of systemic cancer and affect 20-40% of all adult cancer patients. Whole-brain radiotherapy and surgical resection of accessible, solitary lesions have been the mainstay of treatment. Recently, chemotherapy has become a more viable treatment option for metastatic brain tumors. Many different drugs and administrative approaches have been shown to be clinically active. Traditional chemotherapy given before or during irradiation can be effective with agents such as cyclophosphamide, cisplatin and etoposide. Nontraditional approaches, such as tempozolomide and intra-arterial administration of carboplatin, have demonstrated activity against recurrent metastatic disease. In early clinical trials of interstitial chemotherapy, biodegradable polymers have shown some clinical efficacy and have been well-tolerated. Molecular approaches are also under investigation in response to new information regarding the metastatic phenotype. Potential targets include growth factor receptors and other protein tyrosine kinases, internal signal transduction pathways, ras activation and matrix metalloprotease activity. New clinical trials will be needed to investigate these new molecular-based therapeutics, alone and in combination with currently available treatment options, to determine the optimal application of chemotherapy to metastatic brain tumors.

Is intra-arterial chemotherapy useful in high-grade gliomas?

Low delivery of common chemotherapeutic drugs to the brain is considered to be a major obstacle for obtaining durable disease control in patients with high-grade gliomas. Intra-arterial drug injection after selective catheterization of cerebral arteries has been performed in some small clinical trials in order to achieve higher drug concentration in the tumor while minimizing systemic exposure. We reviewed the results in terms of response and toxicity from studies with intra-arterial administration of nitrosoureas and platinum derivatives, as well as the principal aspects and perspectives of the new strategy of blood-brain barrier disruption with osmotic agents or bradykinin analogs. No superiority of intra-arterial chemotherapy over its intravenous counterpart has been demonstrated so far and although the incidence of serious neurotoxicity is reduced, the risk of untoward acute complication still contraindicates internal carotid or vertebral artery catheterization for chemotherapy administration outside the setting of well-controlled clinical trials.

Strategies for increasing drug delivery to the brain: focus on brain lymphoma

The blood-brain barrier (BBB) is a gate that controls the influx and efflux of a wide variety of substances and consequently restricts the delivery of drugs into the central nervous system (CNS). Brain tumours may disrupt the function of this barrier locally and nonhomogeneously. Therefore, the delivery of drugs to brain tumours has long been a controversial subject. The current concept is that inadequate drug delivery is a major factor that explains the unsatisfactory response of chemosensitive brain tumours. Various strategies have been devised to circumvent the BBB in order to increase drug delivery to the CNS. The various approaches can be categorised as those that attempt to increase delivery of intravascularly administered drugs, and those that attempt to increase delivery by local drug administration. Strategies that increase delivery of intravascularly injected drugs can manipulate either the drugs or the capillary permeability of the various barriers (BBB or blood-tumour barrier), or may attempt to increase plasma concentration or the fraction of the drug reaching the tumour (high-dose chemotherapy, intra-arterial injection). Neurotoxicity is a major concern with increased penetration of drugs into the CNS or when local delivery is practised. Systemic toxicity remains the limiting factor for most methods that use intravascular delivery. This review evaluates the strategies used to increase drug delivery in view of current knowledge of drug pharmacokinetics and its relevance to clinical studies of chemosensitive brain tumours. The main focus is on primary CNS lymphoma, as it is a chemosensitive brain tumour and its management routinely utilises specialised strategies to enhance drug delivery to the affected CNS compartments.

A model of blood-brain barrier permeability to water: accounting for blood inflow and longitudinal relaxation effects

A noninvasive technique for measuring the permeability of the blood-brain barrier (BBB) to water could help to evaluate changes in the functional integrity of the BBB that occur in different pathologies, such as multiple sclerosis or growth of brain tumor. Recently, Schwarzbauer et al. (Magn Reson Med 1997;37:769-777) proposed an MR method to measure this permeability based on the T(1) reductions induced by injecting various doses of paramagnetic contrast agent. However, this method may be difficult to implement in a clinical environment. Described here is a two-point technique, in which a spatially selective inversion is used to measure T(1) prior to and after injection of an intravascular contrast agent. Measurements made in the rat brain are compared to numerical simulations generated with a physiological model that accounts for blood flow and includes two different blood volumes: nonexchanging and exchanging blood volumes. Our results suggest that BBB permeability could be evaluated from the change in T(1) caused by the vascular contrast agent. This technique might provide an approach for monitoring changes in BBB permeability to water in clinical studies.

Mixing during intravertebral arterial infusions in an in vitro model

Regional delivery of drugs can offer a pharmacokinetic advantage in the treatment of localized tumors. One method of regional delivery is by intra-arterial infusion into the basilar/vertebral artery network that provides local access to infratentorial tumors, which are frequent locations of childhood brain cancers. Proper delivery of drug by infused solutions requires adequate mixing of the infusate at the site of infusion within the artery lumen. Our mixing studies with an in vitro model of the vertebral artery network indicate that streaming of drug solution is likely to occur at low, steady infusion rates of 2 ml/min. Streaming leads to maldistribution of drug to distal perfused brain regions and may result in toxic levels in some regions while concurrently yielding subtherapeutic levels in adjacent regions. According to our model findings, distribution to both brain hemispheres is not likely following infusion into a single vertebral artery even if the infusate is well-mixed at the infusion site. This outcome results from the unique fluid flow properties of two converging channels, which are represented by the left and right vertebral branches converging into the basilar. Fluid in the model remains stratified on the side of the basilar artery served by the infused vertebral artery. Careful thought and planning of the methods of intravertebral drug infusions for treating posterior fossa tumors are required to assure proper distribution of the drug to the desired tissue regions. Improper delivery may be responsible for some noted toxicities or for failure of the treatments.

Chemotherapeutic dose intensification for treatment of malignant brain tumors: recent developments and future directions

Despite a large amount of research on malignant brain tumors over the past 70 years, the prognosis for most tumor types is poor. One current focus of research is increasing dose intensity of chemotherapeutic agents. Various ways to increase dose intensity include high-dose chemotherapy followed by stem cell rescue (eg, bone marrow transplant), blood-brain barrier disruption or use of RMP7 to increase transvascular drug delivery, local delivery of chemotherapeutic agents (convection enhancement or clysis, antibody conjugates, and biodegradable polymers), chemoprotective agents, and tumor sensitizers. Improved identification of patients likely to respond to a given regimen may also increase the effectiveness of chemotherapy. We also discuss approaches to improve the design of nonrandomized trials by identifying and controlling potential confounding variables. This will improve the quality of individual studies and perhaps the comparability across studies.