Metabolic, molecular imaging useful in predicting brain tumor treatment response

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Researchers detailed how the use of metabolic or molecular imaging in brain tumor measurement can help determine a patient's response to treatment and is an effective predictor of survival, according to a study presented at SNM 2007 in Washington, D.C.

"Our study opens the door to the possibility that brain tumor patients may live longer and respond better to drug treatments," said Wei Chen, assistant professor in the Department of Molecular and Medical Pharmacology at the David Geffen School of Medicine, University of California, Los Angeles. "Malignant brain tumors are very difficult to treat. Typically, patients live for three months without treatment and up to a year with treatment."

Using positron emission tomography (PET) imaging—with the radiotracer FLT (fluorothymidine)—the researchers were able to determine within one or two weeks whether patients were responding well to the drugs bevacizumab and irinotecan. Bevacizumab is an antiangiogenic agent, which inhibits the development of blood vessels that supply blood and oxygen that contribute to a tumor's growth.

"Until this study, there were no reliable predictors of therapeutic response for patients with primary brain tumors undergoing treatment with these types of drugs," said Chen.

This type of quick response time is much more rapid than what can be expected with the traditionally used magnetic resonance imaging (MRI). Using MRI, it can be difficult to tell tumor growth from changes caused by treatment, and it could take months before it's known whether a patient is responding to treatment, said Chen.

"We studied the predictive value of PET with FLT, a marker of cell proliferation, in patients with recurrent malignant brain tumors,” said Chen. "We used molecular imaging to measure the changes of metabolism in tumor cells," and FLT-PET provided much higher response rates than MRI, she explained.

Additionally, the research shows the FLT-PET imaging is predictive of patients' outcomes—indicating that in those cases where patients responded to drug treatment, they lived three times as long as those who did not, she added.

"FLT-PET—as an imaging biomarker—is strongly predictive of overall survival for these patients with brain cancer," she noted. "No matter one's age, number of times cancer recurred or number of prior drug treatments—FLT-PET was the most powerful independent predictor of survival," she said.