June 27, 2003

Experimental imaging technique details spread of prostate cancer

A study conducted at the MGH and a Dutch hospital finds that a new MRI technique may be able precisely to identify the spread of prostate cancer to lymph nodes. Published in the June 19 issue of the New England Journal of Medicine, the report details how high-resolution MR studies using an iron-oxide-containing contrast agent accurately localized tumor metastases. The imaging agent currently is being evaluated for FDA approval.

"These techniques allow us to clearly distinguish between benign and malignant nodes and to construct three-dimensional maps to guide surgical planning," says lead author Mukesh Harisinghani, MD, of MGH Radiology.

Standard practice in treating prostate cancer has been for lymph nodes adjacent to the prostate gland to be analyzed for the presence of cancer, but metastases can appear in nodes beyond the area of analysis. Standard imaging can only identify enlarged nodes that may contain tumor cells; but some enlarged nodes prove benign, and metastases can occur in very small nodes.

Eighty participants, all of whom had been diagnosed with prostate cancer, had preliminary high-resolution abdominal MR studies done before receiving intravenous infusions of the iron-containing contrast agent. A second set of MR studies was taken 24 hours later. After the imaging studies, the patients received standard prostate cancer treatment, and nine patients had additional lymph nodes removed based on results of the imaging. The MR studies found cancer in 63 of the 334 nodes imaged. Pathologic examination confirmed that no tumor had been missed by the technique; in fact more than 70 percent of the metastases were so small they would not have been identified as malignant by current imaging techniques. 

"The experimental aspects of this technique have been tested and validated at the MGH during the last decade, and we believe it has the potential of revolutionizing cancer staging," says Ralph Weissleder, MD, PhD, director of the MGH Center for Molecular Imaging Research and the senior author. The research team — which includes Shahin Tabatabaei, MD, and Peter Hahn, MD, PhD — also is optimistic that this approach could be applied to several other forms of cancer.