Studying the heterogeneity of brain tumors using medium throughput LOH analysis

Temozolomide single-agent chemotherapy for newly diagnosed anaplastic oligodendroglioma

The treatment of patients with anaplastic oligodendroglioma (AO) has been significantly impacted by the molecular detection of loss of sequences on chromosomes 1p and 19q. We performed a clinical trial to prospectively evaluate the safety of treating patients with AO with temozolomide (TMZ) alone in patients with chromosome 1p/19q loss and with chemo-radiation in patients not harboring this loss. Forty-eight patients were enrolled, 36/48 (75%) with evidence of chromosome 1p/19q loss treated with TMZ alone and 12/18 (25%) without such losses, treated with pre-radiation TMZ followed by chemo-radiation. Despite more aggressive treatment, patients without 1p/19q loss had a shorter progression-free survival (PFS) of 13.5 months. With a median follow-up time of 32 months, patients with 1p/19q LOH had a median TTP of 28.7 months. Patients with AO with 1p/19q LOH can be safely treated with single-agent TMZ and do not appear to experience earlier or more frequent tumor progression. This treatment regimen should be studied as part of a formal randomized clinical trial.

Gliomas: advances in molecular analysis and characterization

BACKGROUND

Gliomas represent the most common primary brain tumor. Despite recent advances in diagnostic imaging, neurosurgical technique, radiation therapy, and chemotherapy, significant advances in accurate prognosis and improved survival have not been achieved. Nevertheless, new developments in molecular biology could have potential impact on the clinical management of patients with these brain tumors. This review will describe the technological advances being used to enrich the classification of gliomas, present specific studies that have successfully used the new technologies to identify molecular subtypes of glioblastoma, and discuss the implications of such enhanced classification and molecular characterizations for the prediction of therapeutic response and the design of future brain tumor therapies.

RESULTS

Innovative techniques using complementary DNA and oligonucleotide microarrays (gene chips), tissue microarrays (tissue chips), and differential immunoabsorption have provided high throughput and potentially comprehensive approaches for the molecular characterization of human gliomas. Alterations of several tumor suppressor genes and oncogenes have already been identified as being critical to glioma transformation and progression. These approaches have led to the subclassification of glioblastoma multiforme into distinct subtypes based on the molecular signatures of the tumors.

CONCLUSIONS

Classifications of gliomas can now be enhanced with new techniques for comprehensive molecular characterization. Improved and efficient molecular profiling of brain tumors is advancing diagnosis/prognosis and identifying targets for novel and rational therapeutic approaches. Neurosurgeons and neuro-oncologists should be aware of these new developments so they can better advise and treat their patients.