Despite recent improvements in traditional mammography¿among them computer-aided detection (CAD) and digital mammography¿too many breast cancers go undiscovered for too long. This is especially true for young women: their denser breast tissue makes small tumors difficult, if not impossible, to find. But a team of scientists from the University of Pennsylvania and Harvard University is working to develop an entirely new way of testing for tumors before they spread. Yesterday Britton Chance, an emeritus professor of biochemistry and biophysics at Penn, described their novel approach at the annual meeting of the American Physical Society in Seattle.

The detection method relies on tricarbo-cyanine, a contrast agent normally used for testing liver function. The researchers inject fluorescent tricarbo-cyanine molecules coated with a special peptide into the bloodstream. The mixture travels to the breast, where it is specifically taken up by malignant cells. These cells, in turn, crack open the peptide cloak to expose the glowing tricarbo-cyanine, which can be detected by a circle of tiny laser diodes in a hand-held sensor.

"In our preliminary test, we had a success rate in the percentage range of the high 80s," Chance says. And the procedure is about to enter phase-II clinical trials in a larger group of women. These trials are being conducted at Dartmouth University and the University of California, Irvine¿as well as at such pharmaceutical companies as Phillips, Siemens, ART and Imaging Diagnostic Systems, Inc. Chance adds that the technique should offer advantages over traditional mammography not only for younger women at risk, but also for women in remote areas. "The proposed hand-held unit has outreach possibilities," he says, "for under-served populations of women who can't get to a clinic or hospital for an X-ray."