Needle-free 'biopsy'
BRAIN tumors could be diagnosed without the need for tissue samples by looking at a "fingerprint" of the chemicals they produce.
While an MRI scan can image a brain tumor, in most cases a biopsy is needed to confirm the type of tumor and how aggressive it is. Inserting a needle into the brain is not only unpleasant for the patient, but also can cause strokes or paralysis in up to 2% of cases, and even death.
Now, John Griffiths at Cancer Research UK's Cambridge Research Institute and his colleagues have put an MRI scanner to an additional use. Certain chemicals are found at much higher levels in tumors than in normal tissue, and their distribution also varies between different types of tumors.
Using a technique called magnetic resonance spectroscopy (MRS), which relies on the fact that the atomic nuclei of different chemicals resonate at different frequencies when stimulated by a magnet, they've established chemical fingerprints for a variety of brain tumors. The technique could potentially be used to diagnose brain tumors and choose the best way to treat them without the need for a biopsy, Griffiths says.
The researchers have built up a database of fingerprints from 91 of the most common types of brain tumors and created software that can diagnose the type and grade of the major tumor types with up to 93% accuracy when used in combination with an MRI scan, which creates an image based on the water content of the patient's tissues. An MRI scan alone is about 80% accurate. The results were presented at a meeting of the European Society for Magnetic Resonance in Medicine and Biology in Warsaw, Poland, in September, 2006.
"The holy grail would be to be able to say we are 95% certain that this is a low or a high- grade tumor and that there is therefore no need for a biopsy," says Jeremy Rees, a neurologist at University College London. Many types of brain tumor can be treated using chemotherapy or radiotherapy, but most radiotherapists are reluctant to proceed without a biopsy. More work is needed before MRS can replace biopsies completely, Rees says.
In time, Griffiths hopes MRS might also be used to look at the chemical fingerprints of other cancer types, such as non-Hodgkin's lymphoma, to see whether they will respond to chemotherapy. "At the moment, a patient can go through months of horrible treatment that isn't going to work," he says.
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