NEW ORLEANSDiffusion-weighted MRI reveals rapid changes in tumor
water diffusion values after successful therapeutic intervention in solid
tumors. It therefore appears capable of predicting treatment response within
days of initiating therapy, Brian D. Ross, PhD, of the University of Michigan,
said at the 92nd Annual Meeting of the American Association for Cancer Research
Diffusion-weighted MRI yields information by testing the integrity of tumor
cell membranes. The system tracks the ease with which water travels microscopic
distances. The unbroken outer membranes of normal cells slow the movement of
the water molecules, but "punctured" membranes around dead or dying
cells allow water to diffuse more freely.
The diffusion-weighted MRI follows the random motion of water in the body,
and yields a number that describes changes in tumor water diffusion values, Dr. Ross explained at a press
Dr. Ross and his colleagues, including Thomas L. Chenevert, MD, who
presented the findings, evaluated the method in rodents and have also obtained
preliminary results in 12 primary brain tumor patients.
One patient, a 13-year-old female, had less than 20% tumor shrinkage after 8
weeks of therapy, which corresponded with a small increase in the diffusion
coefficient of the tumor. "In this case, we could detect what we think is
very small cell kill, even though it is not a significant therapeutic effect.
In a clinical trial, this might indicate that a dose escalation or different
route of administration should be tried," Dr. Ross said.
A second patient in the series had no regression of tumor, which correlated
well with the total lack of change in diffusion, he reported. Outcomes are
pending on other patients.