Functional magnetic resonance imaging that measures flow of water molecules can help predict early in the course of therapy if a patient’s malignant brain tumor will respond to chemotherapy or radiation, according to an article posted online March 28th by the Proceedings of the National Academy of Sciences (USA).

Researchers at the University of Michigan Comprehensive Cancer Center developed the assessment, which they call a functional diffusion map. They used a magnetic resonance imaging scan that tracks diffusion of water through the brain and mapped changes in diffusion from the start of therapy to three weeks later. Tumor cells block the flow of water, so as those cells die, water diffusion changes.

In the study of 20 people with malignant brain tumors, researchers found that any change in the functional diffusion map predicted 10 weeks before traditional techniques if the tumor was responding to chemotherapy or radiation therapy. This has potential to spare patients from weeks of a grueling treatment regimen that is not working and gives doctors the opportunity to switch patients to a therapy that may be more effective.

With use of diffusion MRI and the functional diffusion map, the American researchers were able to predict with 100 percent accuracy after three weeks of treatment whether therapy would be effective ? 10 weeks before traditional methods would show a response.

“This is an important issue in terms of patient quality of life. Do you want to go through seven weeks of treatment only to find two months later that it had no effect? Using MRI tumor diffusion values to accurately predict the treatment response early on could allow some patients to switch to a more beneficial therapy and avoid the side effects of a prolonged and ineffective treatment,” said Brian Ross, PhD.

In the study, 20 participants with brain tumors underwent diffusion MRI before beginning a new treatment involving chemotherapy, radiation therapy or a combination. Three weeks later, they had another diffusion MRI. After finishing their treatment, the participants underwent standard MRI to determine whether their tumor responded to the therapy.

After three weeks - more than two months before the final MRI scan - researchers found significant differences between the patients’ scans. Some areas reflected an increase in water diffusion, suggesting tumor cell death; other areas saw a decrease in diffusion, which Ross said could be accounted for by the swelling some cells undergo before dying; and in some participants, researchers saw no change in diffusion.

“In the end, we found if the diffusion changes in any way, up or down, it correlates to a positive outcome. The magnitude or amount of change relates to the effectiveness of treatment. This indicates a different mixture of cell death pathways within the tumors. In the end, any change is good. When you think about it, if the treatment is not having an effect, the tumor will continue to grow without any change to water diffusion,” Ross said.

Researchers plan to test the technique with breast cancer and head and neck cancer.