MRI combo spots prostate cancer treatment failure

NEW YORK (Reuters Health) - Two imaging modalities used in combination -- dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and diffusion-weighted imaging (DWI)-MRI -- can accurately spot residual or recurrent prostate cancer in patients treated with a fairly new treatment called high-intensity focused ultrasonic ablation, a new study shows.

Together these two imaging modalities are better than either modality alone, researchers say.

High-intensity focused ultrasonic ablation is becoming more common as a prostate cancer treatment option, particularly in patients who can't or don't want to undergo a radical prostatectomy (removal of the prostate), they note.

Dr. Chan Kyo Kim, from Samsung Medical Center in Seoul, Korea, and colleagues evaluated these imaging modalities in 27 patients whose prostate-specific antigen (PSA) levels rose after treatment -- a sign that the cancer may have returned.

In 18 of these patients, biopsy confirmed local tumor progression after treatment.

DCE-MRI and DWI-MRI had about a 72 percent accuracy rate in determining which patients needed additional treatment because they had residual or recurrent cancer.

DWI-MRI had fewer false positives than DCE-MRI, but DCE-MRI had fewer false negatives.

"After high-intensity focused ultrasonic ablation, the normal anatomy of the prostate gland is completely lost or deformed, making it difficult to distinguish benign tissue from cancer," Dr. Kim said in a statement.

The present findings suggest that the combination of DCE-MRI and DWI-MRI, which only takes about 7 minutes to perform, is best for this purpose.

SOURCE: American Journal of Roentgenology, May 2008.