Functional MR predicts prostate cancer response to treatment

Measuring the diffusion of water within bone tumors may indicate whether the tumors, caused by the metastasis of prostate or breast cancer, are responding to treatment, according to preclinical research at the University of Michigan Comprehensive Cancer Center.

The developers of the technique have previously carried out MR functional diffusion mapping in people with brain tumors, finding that the test can identify patients who are responding to chemotherapy or radiation after only three weeks of therapy - more than two months earlier than traditional tests. If their most recent work can be translated to the clinic, the newly developed technique could fill a gap in the management of patients with cancers that have spread to the bone.

"Currently, we have no way of detecting bone tumor response to therapy," said Brian D. Ross, Ph.D., a professor of radiology and biological chemistry. "The magnitude of this problem is huge - as many as 500,000 people in the U.S. have metastatic breast or prostate cancer to the bone."

Ross, codirector of the molecular imaging program at the UM Comprehensive Cancer Center, and Alnawaz Rehemtulla, Ph.D., a professor of radiation oncology and environmental health sciences, have founded a company in Ann Arbor, called ImBio, that has licensed the commercialization rights of the diffusion technique from the university. Their software, which tracks the movement of water in bone, runs on Cedara Software's I-Response workstation, which is being developed by the Merge Healthcare subsidiary specifically to serve as a platform on which radiologists and radiation oncologists can work together.

The UM researchers used I-Response in their preclinical studies. Cedara continues to develop the platform for commercial release to OEMs later this year, according to Chris Wiedmann, Cedara product manager for oncology.

"I-Response will provide the framework for the technology and workflow of functional diffusion mapping," he told DI SCAN.

In studies on mice, functional diffusion mapping using MR and the specially designed software tracked bone water diffusion during the course of the animals' chemotherapy. Because tumor cells slow the movement of water, the death of these cells is accompanied by an increase in water diffusion. An increase in diffusion, therefore, indicated effectiveness of the treatment in this animal model of prostate cancer metastasis.

In the study, which was reported in the April 15 issue of Cancer Research, untreated mice showed little or no change in water diffusion, while the functional diffusion map changed increasingly in the treated mice over the three weeks of their therapy. Using functional diffusion map analysis, the researchers identified a statistically significant change in diffusion as early as seven days after the start of treatment. At the end of the study, they removed the tumors and found the functional diffusion map predicted the tumors' response to treatment.

Tumors or portions of a tumor that showed no change on the functional diffusion map showed no changes in specimens removed from the animals. The map accurately predicted the cells that were responsive to the chemotherapy.

"The functional diffusion map could serve as an early biomarker indicating that a tumor is responding to treatment," said author Dr. Kenneth Pienta, director of the urologic oncology program at the UM Comprehensive Cancer Center. "This could allow patients to switch to an alternative therapy without wasting time on a treatment that is not working."