THURSDAY, March 27, 2008 (HealthDay News) -- A sophisticated imaging technique can detect the changes in blood flow in the brain that often herald the emergence of highly malignant brain tumors, researchers report.
The British researchers said the discovery could one day help doctors time the treatment of brain tumors known as low-grade gliomas by using MRI technology to measure changes in "relative cerebral blood volume."
"The clinical treatment of low-grade gliomas is controversial because none of the therapeutic options is curative and patients are often young and clinically well," said Adam D. Waldman, one of the lead investigators and imaging research director at Imperial College National Health Service Trust in London.
"Almost all low-grade gliomas, however, transform into aggressive high-grade tumors, although the timing of that is unpredictable," Waldman added. High-grade tumors are considered very malignant and grow quickly, he explained.
Finding a "marker" for that transformation was the goal of a three-year study by Waldman and his colleagues. Using perfusion MRI imaging with 13 patients, they found that increases in relative cerebral blood volume are a signal that the low-grade glioma is turning into a high-grade glioma. For brain tumors to grow, new blood vessels are formed during a process known as angiogenesis. These abnormal vessels increase blood flow to the tumor, according to the study.
"Essentially what we think perfusion imaging is demonstrating are the earliest changes in the tumor that go along with malignant change," Waldman said.
The findings will be published in the April issue of Radiology.
Perfusion MRI can detect the progression of malignant brain tumors at least 12 months earlier than current monitoring, the study authors suggested. They recommend that it be used routinely to identify patients who could benefit from early treatment.
Dr. Annick Desjardins, a neuro-oncologist and associate in the department of medicine at Duke University Medical Center, said low-grade gliomas occur less frequently than high-grade gliomas and are difficult to treat. The lowest level of gliomas -- grade one -- hasn't infiltrated the brain yet and can be cut out, she explained. But grade two gliomas -- the type studied by Waldman and his team -- have infiltrated the brain and aren't easy to remove, she said.
A doctor who is following a patient has no way to tell if the tumor will be stable for 10 years or progress in the next three months, Desjardins said. "Early detection will probably allow us to control those tumors over a longer period of time," she said, before adding, "We don't have those data at this particular time to prove that."
Dr. Paul Graham Fisher, an associate professor of neurology and pediatrics at Stanford University School of Medicine, said perfusion MRI technology is widely available at bigger city and academic medical centers. The use of perfusion MRI detailed in the new study provides a noninvasive technique and "the less invasive you can be, the better it will be for patients in the long run," he said.
But, Fisher added, "The only sad part is that the imaging and diagnostics are advancing much faster than the therapeutics. Hand-in-hand, they are critical to each other." While the new ability to detect changes in low-grade gliomas suggested by Waldman's group doesn't promise better therapies or cure rates, "it is encouraging," he said.
More information
To learn more about brain tumors, visit the U.S. National Institute of Neurological Disorders and Stroke.
