For cancer patients, consider the advantages of being able to tell, just halfway into treatment, whether it will successfully shrink the tumor or if the cancer will continue to grow.

That’s what University of Michigan researchers are finding with a special type of M-R-I scan for patients with deadly brain tumors.

After only three weeks of chemotherapy or radiation, the test identifies who is responding to the treatment and who isn’t. That’s more than two months sooner than traditional tests.

The new test is called a functional diffusion map. In a study of thirty-four patients with a type of brain tumor called high-grade glioma [glee-oh-mah], doctors used a magnetic resonance imaging scan that tracks the diffusion, or movement, of water through the brain.

The researchers mapped the changes in water movement at the start of therapy, then compared it with water movement patterns three weeks later. The tumor cells restrict the movement of water, so as those cells die, water diffusion changes. The predictions of treatment response corresponded to patients’ survival.

An early measure of tumor response like this could help doctors identify during the course of treatment who might benefit from a second-line therapy. That could spare patients from a grueling treatment regimen that’s not working.

The study results appeared recently in the Proceedings of the National Academy of Sciences.

Researchers believe this special M-R-I imaging test also could apply to other cancer types, including breast, head and neck, prostate and liver.