Neuroimaging clinics of North America
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Neuroimaging Clin. N. Am. · Nov 2002
ReviewInnovations in design and delivery of chemotherapy for brain tumors.
Effectiveness of chemotherapy in patients with brain tumors is hampered by the presence of the blood-brain barrier and drug resistance. In recent years, significant progress has been made in devising innovative methods of design and delivery of chemotherapy for brain tumors. This article has surveyed the issues of blood-brain barrier and drug resistance and explored some of the strategies used to circumvent problems associated with chemotherapy failure in patients with brain tumors.
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The grave outlook for malignant glioma patients in spite of improvements to current modalities has ushered in new approaches to therapy. Viruses have emerged on the scene and gained attention for their ability to play essentially two roles: first, as vectors for therapeutic gene delivery and second, as engineered infectious agents capable of selectively lysing tumor cells. ⋯ Clinical oncolytic studies, on the other hand, have evaluated a conditionally replicating HSV as an antineoplastic agent. Despite some promise afforded by these trials, further studies are warranted; the investigation of additional viruses to play these roles is inevitable and is now precedented.
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Neuroimaging Clin. N. Am. · Nov 2002
ReviewViral imaging in gene therapy noninvasive demonstration of gene delivery and expression.
Gene therapy is a rapidly developing modality of treatment, with applications in acquired and inherited disorders. Gene delivery vehicles ("vectors") are the main impediment in the evolution of gene therapy into a clinically acceptable mainstream therapy. Vectors based on viral particles are the most commonly used vehicles to carry genes to the organs and tissues of interest. ⋯ Recent progress in viral vector production and better understanding of molecular aspects of vector delivery and targeting issues has created the need for imaging techniques that would be useful in addressing the problems and opportunities inherent in viral gene therapy development. Two integral components of gene therapy monitoring, the imaging of gene delivery and the imaging of resultant exogenous gene expression, are recognized. These molecular imaging components provide a realistic means for assessment of safety and efficacy of preclinical and clinical development of gene therapy.
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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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Assessment of the oxygenation status of brain tumors has been studied increasingly with imaging techniques in light of recent advances in oncology. Tumor oxygen tension is a critical factor influencing the effectiveness of radiation and chemotherapy and malignant progression. Hypoxic tumors are resistant to treatment, and prognostic value of tumor oxygen status is shown in head and neck tumors. ⋯ Quantification of cerebral blood oxygen saturation using MR imaging has promising clinical applications; however, technical difficulties have to be resolved. Blood oxygen level dependent MR imaging is an emerging technique to evaluate the cerebral blood oxygen saturation, and it has the potential and versatility to assess oxygenation status of brain tumors. Upon improvement and validation of current MR techniques, better diagnostic, prognostic, and treatment monitoring capabilities can be provided for patients with brain tumors.