A simple magnetic resonance imaging (MRI) test involving breathing oxygen might help oncologists determine the best treatment for some cancer patients, report researchers at UT Southwestern Medical Center.
Prior research has shown that the amount of oxygen present in a tumor can be a predictor of how well a patient will respond to treatment. Tumors with little oxygen tend to grow stronger and resist both radiotherapy and chemotherapy. Until now, however, the only way to gauge the oxygen level in a tumor, and thus determine which treatment might be more effective, was to insert a huge needle directly into the cancerous tumor.
The new technique, known as BOLD (blood oxygen level dependent) MRI, can detect oxygen levels in tumors without the need for an invasive procedure. The patient need only be able to breathe in oxygen when undergoing an MRI.
"The patient simply inhales pure oxygen, which then circulates through the bloodstream, including to the tumors," said Dr. Ralph Mason, professor of radiology, director of the UT Southwestern Cancer Imaging Center and senior author of a study appearing online and in a future edition of Magnetic Resonance in Medicine. "Using MRI, we can then go in and estimate how much oxygen a particular tumor is taking up, providing us some insight into how the tumor is behaving and what sort of treatment might be effective."
The most important finding, Dr. Mason said, is that BOLD MRI performed as well as the standard yet more invasive procedure for viewing tumors. That method, known as FREDOM (fluorocarbon relaxometry using echo planar imaging for dynamic oxygen mapping) MRI, requires the injection of a chemical called a reporter molecule directly into the tumor.
"The BOLD technique appears to indicate accurately the oxygen levels in tumors," Dr. Mason said. "Because BOLD is immediately applicable to patients, this holds promise as a new method for predicting response to therapy."
BOLD MRI has been used extensively in studying brain function, but the procedure has only recently begun to be used to assess blood oxygenation and vascular function in tumors.