New imaging technique may predict prostate tumor response to therapy

A new imaging technique, known as a functional diffusion map, can measure the effectiveness of treatment for prostate cancer metastatic to bone. The technique involves measuring diffusion of water within tumors.

Detecting bone tumor response to therapy currently is not possible, even with all of the available imaging options. As many as 500,000 people in the United States have metastatic breast or prostate cancer to the bone, according to study author Brian D. Ross, PhD, of the University of Michigan Medical School.

The team studied metastatic prostate cancer in mice. Half the mice were given chemotherapy to treat the cancer, while the remaining mice served as controls. A functional diffusion map analysis, using special software and MRI scans of bone tumors, found the mice that did not receive therapy had little or no change in tumor water diffusion, while the treated mice had progressively increasing changes in the functional diffusion map over the 3 weeks of treatment (Cancer Res 2007; 67:3524-8). Researchers could identify a statistically significant change in diffusion as early as 7 days after treatment began.

At the end of the study, the researchers removed the tumors and found the functional diffusion map had predicted the tumors' response to treatment. Tumors or portions of tumors that had appeared not to change on the functional diffusion map had not responded to treatment, while the map accurately predicted which cells had responded to chemotherapy.