Optical biopsy studied as breast cancer treatment aid

An OBS is a real-time probe based on white-light interaction with tissue, which can be used either through an endoscope or a biopsy needle. The system consists of small optical fibers that shine tiny bursts of light onto tissue and then collect the scattered light traveling through the tissue. A computer then analyzes the scattered light.

OBS technology works because cancerous tissue scatters and absorbs light differently than normal tissue. A computer uses artificial intelligence and pattern recognition codes to analyze the scattered light spectra and discern the spectra of normal tissue from diseased tissue.

"Breast cancer is very complicated because breast tissue consists of a wide variety of tissue types," said Irving Bigio, formerly with the Laboratory's Bioscience Division and now at Boston University. "Types of cancer tissues from the breast vary greatly, as do types of normal tissue, so it's a difficult process doing diagnos- tics." Bigio and Paul Ripley, a post doc at the Laboratory from the United Kingdom, are currently working with doctors at the University College of London Medical School on the OBS clinical breast cancer studies.

So far, data from the clinical studies being conducted by the UK collabo- rators are promising. The OBS data agree with findings from standard pathology more than 80 percent of the time, based on two parameters: sensitivity and specificity. Sensitivity refers to the instrument's ability to find cancer when there is cancer, and specificity refers to the instrument's ability to discern cancerous tissue from healthy tissue.

"We're very encouraged by these results, although preliminary," said Bigio." The fact that we're getting this level of agreement with results from pathology means that the OBS has excellent potential for aiding doctors during breast cancer surgery."

In another aspect of the research, Bioscience Division's Judith Mourant is studying the properties of tissue that affect light scattering and make systems like OBS predictors of cancerous tissue. Light scatters from an object depending on its composition and shape. Consequently, one might expect that the scattering of light from tissue would change when the form and structure of the tissue changes. Mourant has had a National Institutes of Health-funded program since 1996 to study how changes in cell structure that accompany carcinogenesis affect light scattering. "One of our first tasks was to determine what structures in the cells scatter light. We now have strong evidence that light is scattered by small, internal cellular structures," Mourant said.

The light scattering from these small, internal cellular structures is particularly important when the light illumination point and the scattered-light detection point are located close to each other on the surface of the tissue. Further, Mourant has studied the light-scattering properties of tumor-causing cells grown in a 3-D culture. She is now using this information to develop more sensitive methods to noninva- sively measure properties of tissue related to cancer-causing cells.

Mourant now is developing fiber optic probes that deliver and detect polarized light, because this provides additional information than garnered with traditional methods.