Response to prostate cancer treatment can be tracked

By David Douglas

NEW YORK (Reuters Health) - Based on experiments in mice, an MRI-based map showing the diffusion of water inside cells can be used to track treatment response in men with metastatic prostate cancer, investigators report in the current issue of Cancer Research.

Imaging tests are useful for detecting cancer that has spread to the bone, senior investigator Dr. Brian D. Ross told Reuters Health, but they do not easily detect response to treatment.

He explained that "the use of diffusion MRI provides an opportunity to follow the random motion of water molecules within the tumor mass. Changes in the diffusion values occur in concert with the underlying treatment-induced changes in tissue."

Ross and colleagues at the University of Michigan Medical School tested the approach in mice injected with prostate cancer cells tagged with a luminescent agent.

The animals were then given chemotherapy or received no therapy. Using functional diffusion map, the researchers were able to detect regions with significantly increased diffusion values after 7 days. This indicated inactivation of the tumor cells.

"As tumor cells are killed," continued Ross, "the space becomes less crowded and the movement or diffusion of water increases, reflecting a less crowded environment."

"In other words, the diffusion of water within tumor tissue can be used as a surrogate for the number of living tumor cells. If a treatment is successful and kills tumor cells, a significant increase in diffusion occurs."

If these findings in mice can be repeated in a clinical trial, he concluded, "then there would be a strong potential for using this approach to follow treatment in individual patients, which could allow for more individualized treatment."

SOURCE: Cancer Research, April 15, 2007.