The results of two UB studies being presented this week at the annual meeting of the American Society for Laser Medicine and Surgery, Inc. demonstrate two new procedures that may help cancer specialists diagnose malignancies at the very earliest stages, when they are most treatable.

One new technique, called optical spectroscopy, allows cancer specialists to determine the malignant status of tissue without using a chemical photosensitizer used in companion studies by building on a tissue's autofluorescence, or natural response to light.

Photodynamic therapy, one of the most recent and promising forms of cancer treatment, relies on the propensity of cancer cells to absorb a chemical photosensitizer more readily than normal cells. When light activates the chemical, causing it to fluoresce, cancer cells stand out from surrounding tissue. Now hyper-light-sensitive, the cancer cells can be destroyed by exposure to light.

UB researchers demonstrated in a companion study that by subjecting precancerous tissue to small doses of a photosensitizer that is usually used in large doses in photodynamic therapy and observing tissue uptake of the drug during transformation to malignancy-a procedure called in vivo fluorescence photometry-they could predict the timeframe when the transformation begins.

This advancement will allow cancer specialists to detect microscopic malignancies that would be undetectable by any other means. Once thoroughly studied, the procedure ultimately will allow specialists to diagnose a malignancy in its earliest stages-when it is most readily treatable-and will help cancer surgeons define the margins of a tumor with pinpoint accuracy prior to surgery.

"Ultimately, we hope to use this procedure routinely to diagnose early changes, which will result in better outcomes, said Thomas S. Mang, UB research associate professor of oral surgery and lead researcher on the study. "We also think it can be used to perform fluorescence-guided biopsies, which will be much more accurate than any method we have now."

Depending on the drug dosage, however, patients would be sensitive to natural light from days for diagnostic use to a few weeks for treatment dosages.

Now, UB laser researchers have demonstrated in animal studies that they can make a "first approximation" characterization of suspicious tissue without injecting chemical photosensitizers.

In this study, the new, diagnostic technique-optical spectroscopy-is based on the natural and unique light spectrum produced by each tissue in response to light.

"When light goes into a tissue, it interacts with tissue components and structures in a specific way," said Mang, who also was lead author on this study. "Each tissue gives you a fingerprint. As a tissue starts to undergo change, its fingerprint changes."

Mang and colleagues tracked and characterized the changing fingerprints as tissue underwent the transformation from normal to malignant, using an animal model. In this manner, they were able to detect when early tissue change begins.

Results showed that stages of tissue transformation showed up in two different ways using laser-induced autofluorescence-the ratio of red-to-green in the normal versus abnormal tissue, and the intensity of the response. Both changed markedly as tissue became malignant. "The most striking feature is the change in the intensity of the signal of the malignant tissue," Mang stated. "This result indicates that the intensity index is a good indication of tissue status, and could be a real aid to early cancer detection."

The research is a cooperative effort of members of the Great Lakes Biomedical Laser Center. Contributing to the investigation were James Kost and Brian C. Wilson of Princess Margaret Hospital, Ontario Cancer Institute in Toronto, and Charles Liebow, UB professor of oral surgery.

The companion study was a joint effort of the UB School of Dental Medicine, Roswell Park Cancer Institute in Buffalo and Buffalo General Hospital, site of a new Photodynamic Therapy Center, which Mang directs.

Other researchers involved in that study were Liebow; Seema Khan, assistant professor of surgery at Syracuse University, and Jean Haar, UB clinical professor of otolaryngology and oral surgery.