Can Non-Invasive Imaging Differentiate Benign from Malignant Brain Tumors?
Abstract & Commentary
By Andrew B. Lassman, MD, Assistant Attending, Department of Neurology, Memorial Hospital for Cancer and Allied Diseases. Dr. Lassman reports no financial relationship relevant to this field of study.
Synopsis: When biopsy of a brain tumor is not possible due to high surgical risk, perfusion MRI can help distinguish tumor types with high sensitivity and specificity.
Source: Weber MA, et al. Diagnostic Performance of Spectroscopic and Perfusion MRI for Distinction of Brain Tumors. Neurology. 2006;66:1899-1906.
The availability of an accurate, non-invasive test for diagnosing tumors of the brain is a holy grail of neuro-oncology. Two tests currently in use or development include magnetic resonance spectroscopy (MRS) and magnetic resonance perfusion (MRP). MRS analyzes metabolic signatures to differentiate necrosis, tumor, or demyelination from normal brain and each other. Various subsets of MRP imaging analyze relative cerebral blood flow, based on the premise that high-grade tumors will exhibit increased cerebral perfusion relative to low-grade tumors, normal brain, and necrosis.
Weber and colleagues performed MRS and MRP on 79 consecutive patients with newly diagnosed primary or metastatic brain tumors, and correlated findings with histology. MRP was superior to MRS, possibly because of false spectroscopic signals resulting from analysis of necrotic areas within high grade gliomas. The sensitivity of MRP for differentiating various lesions from each other was well over 90% in several instances, such as glioblastomas vs CNS lymphomas and glioblastomas vs metastases. However, the specificity in these comparisons did not exceed 80%. While the sensitivity is impressively high, the sensitivity remains too low for routine replacement of biopsy in diagnostic evaluations. Similar results were obtained when attempting to differentiate high grade from medium- and low-grade gliomas.
Commentary
Histological confirmation by a trained neuropathologist remains the gold standard for diagnosis of mass lesions in the brain. However, for patients with surgically inaccessible tumors or with significant comorbidities that increase the risks of surgical intervention, MRP is an important advance that may allow therapeutic planning in the absence of histology in the context of a high false negative rate. An additional question, not addressed in this study, is the utility of MRP (and MRS) in evaluating response of brain tumors to novel anticancer drugs. Several ongoing studies are using MRP to assess the molecular effects of pathway inhibitors on brain tumors, when obtaining tissue during therapy is difficult or impossible for both practical and ethical reasons.
When biopsy of a brain tumor is not possible due to high surgical risk, perfusion MRI can help distinguish tumor types with high sensitivity and specificity.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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