Neuroimaging clinics of North America
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As an immunization platform for brain tumors, dendritic cells supply an impressive host of advantages. On the simplest level, they provide the safety and tumor-specificity so wanted by current therapeutic options. ⋯ Directions to take now include the identification of new tumor-specific and tumor-associated antigens; the determination of the optimal dendritic cell subtype, generation, loading method, maturation state, dose, and route of delivery for immunizations; the further characterization of dendritic cells and their activities; and, potentially, the discovery of ways to pulse dendritic cells efficiently in vivo. Preclinical studies continue to play an important role in refining this form of active immunotherapy.
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Neuroimaging Clin. N. Am. · Nov 2002
ReviewMolecular abnormalities and correlations with tumor response and outcome in glioma patients.
Molecular analysis approaches hold promise to refine the management of patients with malignant gliomas. An important step in the application of these techniques to guide clinical decision-making involves transitioning these approaches from the research setting into the clinical diagnostic arena, using methods that can be performed rapidly and reliably on surgically obtained tumor specimens. ⋯ An associated challenge involves demonstrating that biological stratification can support therapeutic stratification that will influence, rather than merely predict, the outcome of patients with brain tumors. The realization of this long-range goal will require the identification of novel therapeutic strategies that hold promise for improving the outcome of molecularly defined subsets of high-grade gliomas, which as a group remain largely resistant to conventional therapies.
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Neuroimaging Clin. N. Am. · Nov 2002
ReviewImportance of hypoxia in the biology and treatment of brain tumors.
The resistance of gliomas to treatment with radiation and antineoplastic drugs may result in part from the effects of the extensive, severe hypoxia that is present in these tumors. It is clear that brain tumors contain extensive regions in which the tumor cells are subjected to unphysiological levels of hypoxia. Hypoxic cells are resistant to radiation. ⋯ During the past 50 years, many attempts have been made to circumvent the therapeutic resistance induced by hypoxia, by improving tumor oxygenation, by using oxygen-mimetic radiosensitizers, by adjuvant therapy with drugs that are preferentially toxic to hypoxic cells, by using hyperthermia, or by devising radiation sources and regimens that are less affected by hypoxia. Past clinical trials have provided tantalizing suggestions that the outcome of therapy can be improved by many of these approaches, but none has yet produced a significant, reproducible improvement in the therapeutic ratio, which would be needed for any of these approaches to become the standard therapy for these diseases. Several ongoing clinical trials are addressing other, hopefully better regimens; it will be interesting to see the results of these studies.
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Neuroimaging Clin. N. Am. · Nov 2002
ReviewAnti-angiogenic agents for the treatment of brain tumors.
It is accepted that novel therapeutic approaches are needed for the majority of patients with malignant brain tumors. The vascularity of many primary brain tumors and the encouraging preclinical studies suggest that antiangiogenic agents have the potential to become an important component of multimodality treatment of patients with brain tumors. The understanding of the biology of angiogenesis is improving rapidly, offering the hope for more specific vascular targeting of brain tumor neovasculature. Neuroimaging techniques evaluating the angiogenic process and the impact of antiangiogenic agents will be an important tool for the rapid development of these novel therapeutic agents.
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A wide variety of metabolic features of brain tumors can be imaged using PET, including glucose metabolism, blood flow, oxygen consumption, amino acid metabolism, and lipid synthesis. Currently, FDG is the most widely available PET tracer for body imaging and brain imaging. Malignant brain tumors, like many other soft tissue tumors, show increased glucose metabolism, which is reflected on FDG-PET imaging. ⋯ Other tracers, such as 11C-methionine and FCH, also avidly accumulate in brain tumors and have the advantage of low background cortical activity. The relationship between degree of uptake of these agents and tumor grade is not established. These tracers may be useful in specific clinical situations, however, such as tumor localization for treatment planning or evaluation of low-grade tumors.