Despite scientific advances in understanding the causes and treatment of human malignancy, a persistent challenge facing basic and clinical investigators is how to adequately treat primary and metastatic brain tumors. The blood-brain barrier is a physiologic obstruction to the delivery of systemic chemotherapy to the brain parenchyma and central nervous system (CNS). A number of physiologic properties make the endothelium in the CNS distinct from the vasculature found in the periphery. Recent evidence has shown that a critical aspect of this barrier is composed of xenobiotic transporters which extrude substrates from the brain into the cerebrospinal fluid and systemic circulation. These transporters also extrude drugs and toxins if they gain entry into the cytoplasm of brain endothelial cells before they enter the brain. This review highlights the properties of the blood-brain barrier, including the location, function, and relative importance of the drug transporters that maintain this barrier. Primary and metastatic brain malignancy can compromise this barrier, allowing some access of chemotherapy treatment to reach the tumor. The responsiveness of brain tumors to systemic treatment found in past clinical research is discussed, as are possible explanations as to why CNS tumors are nonetheless able to evade therapy. Finally, strategies to overcome this barrier and better deliver chemotherapy into CNS tumors are presented.

https://clincancerres.aacrjournals.org/content/clincanres/13/6/1663.full.pdf

The blood-brain barrier and cancer: transporters, treatment, and Trojan horses.

Cytostatic antibiotics of the anthracycline class are the best known of the chemotherapeutic agents that cause cardiotoxicity. Alkylating agents such as cyclophosphamide, ifosfamide, cisplatin, carmustine, busulfan, chlormethine and mitomycin have also been associated with cardiotoxicity. Other agents that may induce a cardiac event include paclitaxel, etoposide, teniposide, the vinca alkaloids, fluorouracil, cytarabine, amsacrine, cladribine, asparaginase, tretinoin and pentostatin. Cardiotoxicity is rare with some agents, but may occur in >20% of patients treated with doxorubicin, daunorubicin or fluorouracil. Cardiac events may include mild blood pressure changes, thrombosis, electrocardiographic changes, arrhythmias, myocarditis, pericarditis, myocardial infarction, cardiomyopathy, cardiac failure (left ventricular failure) and congestive heart failure. These may occur during or shortly after treatment, within days or weeks after treatment, or may not be apparent until months, and sometimes years, after completion of chemotherapy. A number of risk factors may predispose a patient to cardiotoxicity. These are: cumulative dose (anthracyclines, mitomycin); total dose administered during a day or a course (cyclophosphamide, ifosfamide, carmustine, fluorouracil, cytarabine); rate of administration (anthracyclines, fluorouracil); schedule of administration (anthracyclines); mediastinal radiation; age; female gender; concurrent administration of cardiotoxic agents; prior anthracycline chemotherapy; history of or pre-existing cardiovascular disorders; and electrolyte imbalances such as hypokalaemia and hypomagnesaemia. The potential for cardiotoxicity should be recognised before therapy is initiated. Patients should be screened for risk factors, and an attempt to modify them should be made. Monitoring for cardiac events and their treatment will usually depend on the signs and symptoms anticipated and exhibited. Patients may be asymptomatic, with the only manifestation being electrocardiographic changes. Continuous cardiac monitoring, baseline and regular electrocardiographic and echocardiographic studies, radionuclide angiography and measurement of serum electrolytes and cardiac enzymes may be considered in patients with risk factors or those with a history of cardiotoxicity. Treatment of most cardiac events induced by chemotherapy is symptomatic. Agents that can be used prophylactically are few, although dexrazoxane, a cardioprotective agent specific for anthracycline chemotherapy, has been approved by the US Food and Drug Administration. Cardiotoxicity can be prevented by screening and modifying risk factors, aggressively monitoring for signs and symptoms as chemotherapy is administered, and continuing follow-up after completion of a course or the entire treatment. Prompt measures such as discontinuation or modification of chemotherapy or use of appropriate drug therapy should be initiated on the basis of changes in monitoring parameters before the patient exhibits signs and symptoms of cardiotoxicity.

Cardiotoxicity of chemotherapeutic agents: incidence, treatment and prevention.

The blood-brain barrier (BBB) excludes the vast majority of cancer therapeutics from normal brain. However, the importance of the BBB in limiting drug delivery and efficacy is controversial in high-grade brain tumors, such as glioblastoma (GBM). The accumulation of normally brain impenetrant radiographic contrast material in essentially all GBM has popularized a belief that the BBB is uniformly disrupted in all GBM patients so that consideration of drug distribution across the BBB is not relevant in designing therapies for GBM. However, contrary to this view, overwhelming clinical evidence demonstrates that there is also a clinically significant tumor burden with an intact BBB in all GBM, and there is little doubt that drugs with poor BBB permeability do not provide therapeutically effective drug exposures to this fraction of tumor cells. This review provides an overview of the clinical literature to support a central hypothesis: that all GBM patients have tumor regions with an intact BBB, and cure for GBM will only be possible if these regions of tumor are adequately treated.

/pdf/is-the-blood-brain-barrier-really-disrupted-in-all-oze6c9iodb.pdf

Is the blood-brain barrier really disrupted in all glioblastomas? A critical assessment of existing clinical data.

Mitoxantrone is a dihydroxyanthracenedione derivative which as intravenous mono- and combination therapy has demonstrated therapeutic efficacy similar to that of standard induction and salvage treatment regimens in advanced breast cancer, non-Hodgkin's lymphoma, acute nonlymphoblastic leukaemia and chronic myelogenous leukaemia in blast crisis; it appears to be an effective alternative to the anthracycline component of standard treatment regimens in these indications. Mitoxantrone is also effective as a component of predominantly palliative treatment regimens for hepatic and advanced ovarian carcinoma. Limited studies suggest useful therapeutic activity in multiple myeloma and acute lymphoblastic leukaemia. Regional therapy of malignant effusions, hepatic and ovarian carcinomas has also been very effective, with a reduction in systemic adverse effects. Mitoxantrone inhibits DNA synthesis by intercalating DNA, inducing DNA strand breaks, and causing DNA aggregation and compaction, and delays cell cycle progression, particularly in late S phase. In vitro antitumour activity is concentration- and exposure time-proportional, and synergy with other antineoplastic drugs has been demonstrated in murine tumour models. Leucopenia may be dose-limiting in patients with solid tumours, whereas stomatitis may be dose-limiting in patients with leukaemia. Other adverse effects are usually of mild or moderate severity although cardiac effects, particularly congestive heart failure, may be of concern, especially in patients with a history of anthracycline therapy, mediastinal irradiation or cardiovascular disease. Mitoxantrone displays an improved tolerability profile compared with doxorubicin and other anthracyclines, although myelosuppression may occur more frequently. Thus, mitoxantrone is an effective and better tolerated alternative to the anthracyclines in most haematological malignancies, in breast cancer and in advanced hepatic or ovarian carcinoma. Further studies may consolidate its role in the treatment of these and other malignancies.

Mitoxantrone. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential in the chemotherapy of cancer.

Mitoxantrone, a synthetic anthracenedione, was developed in the 1980s as a doxorubicin analogue in a program to find a cytotoxic agent with decreased cardiotoxicity compared with doxorubicin. It was approved by the FDA in 1987 for the treatment of adult acute myeloid leukemia and in 1996 for symptomatic hormone-refractory prostate cancer. In 2000, mitoxantrone was approved by the FDA for the treatment of worsening relapsing-remitting multiple sclerosis (MS), secondary progressive MS, and progressive-relapsing MS. Mitoxantrone is taken up rapidly by tissues, from which it is released slowly, and the terminal half-life ranges from 8.9 hours to 9 days. The highest concentrations of the drug are typically found in the thyroid, liver, and heart, and the drug persists in the body for as long as 272 days. Mitoxantrone is effective in reducing disease progression through a variety of different mechanisms of action. For example, it suppresses the proliferation of T cells, B cells, and macrophages. It impairs antigen presentation and decreases the secretion of proinflammatory cytokines. Mitoxantrone enhances T-cell suppressor function and inhibits B-cell function and antibody production. Finally, it inhibits macrophage-mediated myelin degradation. Compared with interferon betas, mitoxantrone has a broad range of actions and has effects on many different types of immune cells.

Mechanism of action of mitoxantrone

A sensitive high-performance liquid chromatography method was used to measure mitoxantrone in autopsy tissue samples of 11 patients who had received the drug iv 10-272 days antemortem. Mitoxantrone was readily detectable in tissues from all patients. Tissue concentrations were proportional to lifetime cumulative dose of mitoxantrone, and decreased very slowly with time. The thyroid and the liver had the highest mitoxantrone concentrations, followed by the heart. These high cardiac concentrations of mitoxantrone could be partially responsible for the occasional case of cardiotoxicity seen with mitoxantrone. The brain had the lowest mitoxantrone concentrations. Organ mitoxantrone concentrations did not conform to a flow-limited model. Tumor mitoxantrone concentrations varied quite markedly from one site to another in the same patient. Tumors generally had lower mitoxantrone concentrations than did surrounding normal tissues. Mitoxantrone concentrations were consistently highest in intrahepatic tumors and lowest in intracerebral tumors. It is unclear whether the low concentrations in brain tumors were due to a partially intact blood-brain barrier or to the fact that most brain tumors had been irradiated prior to mitoxantrone administration. Further studies are warranted to more fully explore the relationship between human tissue mitoxantrone concentrations and efficacy and toxicity.

Human autopsy tissue concentrations of mitoxantrone.

Mitoxantrone 5–6 mg/m2 was administered IV to 10 consenting patients prior to surgical resection of an intracerebral tumor. Plasma pharmacokinetic parameters were calculated and concentration of mitoxantrone in intracerebral tumors was determined. Concentrations of mitoxantrone were also determined in autopsy tissues of one of the patients who expired 192 days after receiving the drug. The plasma pharmacokinetics were best described by a 3 compartment model, with a t1/2γ of 4.74±5.53 h. Mitoxantrone concentrations in the intracerebral tumors were potentially cytotoxic and ranged from 4 to 322 ng/g. In all but one case, mitoxantrone concentration was higher in tumor than in concurrent plasma samples. There was no obvious relation between tumor mitoxantrone concentration and peak plasma mitoxantrone concentration or time from mitoxantrone administration to tumor removal. Low grade gliomas and viable tumors tended to have lower mitoxantrone concentrations than did other tumor types and necrotic tumors. In the patient undergoing autopsy, highest mitoxantrone concentrations were found in liver, thyroid and heart.

Human central nervous system and plasma pharmacology of mitoxantrone.

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Human autopsy tissue concentrations of mitoxantrone.

Human central nervous system and plasma pharmacology of mitoxantrone.