A light-sensitive probe is being developed to help doctors spot breast cancer in some of the 70,000 American women each year whose malignancies fail to show up in needle biopsies.

The technology also holds the potential of minimizing the trauma associated with the procedure, in which a hollow needle the width of a pencil is used to collect small tissue samples for testing.

Doctors now rely on X-rays or ultrasound images to guide the needle to the area in question. They may take a dozen tissue samples to be sure they do not miss anything. Yet sometimes they do.

"If you're in the wrong spot and you don't get the cancer, then you're basically concluding that this woman doesn't have a disease that needs to be treated," said Nirmala Ramanujam, Ph.D., assistant professor of biomedical engineering at the University of Wisconsin-Madison.

Missed diagnoses occur in as many as 70,000 American women each year, she said. Another 60,000 women have repeat biopsies because the initial results are inconclusive.

Ramanujam, graduate students Carmalyn Lubawy and Changfang Zhu, and radiologist Elizabeth Burnside, M.D., have developed thin, fiber-optic probes that can be threaded through the hollow channel of a biopsy needle to its tip. The probe, together with X-ray or ultrasound images, could ensure that the biopsy needle accurately reaches its target. If successful, Ramanujam's optical probes could be used as an adjunct to standard biopsies.

The probe emits light at specific wavelengths and then collects the reflected light and fluorescence for analysis. The researchers look at how much light is absorbed by tissue and reemitted as fluorescence. They also measure how much light is scattered. Various components of tissue-such as amino acids, proteins, enzymes and blood-absorb and scatter light in specific ways. Tumors interact with light differently than normal tissue does.

Preliminary testing in 56 breast tissue samples from 37 women showed that the optical analysis correctly identified cancer with more than 90 percent accuracy. Further testing will begin in August 2004 on 250 patients.

SOURCES:
Annals of Surgical Oncology, January 2004
The Whitaker Foundation (http://www.whitaker.org)