Optical probe might find missed breast cancers

A light-sensitive probe is being developed to help doctors spot breast cancer in women whose malignancies fail to show up in needle biopsies.

The technology also holds the potential of minimising 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 Whitaker investigator Nirmala Ramanujam, PhD, 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 have developed thin, fibre-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. Tumours 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% accuracy. Further testing will begin in August on 250 patients.

The research group has fine-tuned the optical probe in preparation for the new study and has won $1.2 million in support for the ongoing research from the US National Cancer Institute and the National Institute of Biomedical Imaging and Bioengineering.

The probes can be trimmed thin enough to fit through a needle smaller than the current 1/4-inch biopsy device. This would make the entire procedure less invasive. Ramanujam has also simplified the analysis by carefully reducing the number of light wavelengths needed to make a diagnosis.

‘Minimizing the number of wavelengths analyzed is advantageous clinically because it lends speed to the process and should require a less complex, more economical instrument,’ Ramanujam’s group reported in a recent issue of the journal Annals of Surgical Oncology.

Ramanujam received a Whitaker Foundation Biomedical Engineering Research Grant in 2001 for research in this area.