ASBS 2009: Seeking to Evaluate Breast Cancer Tissue Margins During Surgery

Nick Mulcahy

April 28, 2009

April 28, 2009 — Of the estimated 150,000 lumpectomies performed every year in the United States in the treatment of breast cancer, about 40% of cases require reoperation because of positive margins that are found postoperatively, according to researchers at Duke University in Durham, North Carolina.

In an effort to reduce the need for resurgery and improve on cosmetic results, these researchers developed a novel optical imaging technique that quickly evaluates tumor margins. The technique could eventually enable surgeons to review tumor-margin status during surgery.

Interim results of a pilot study of the new technique, called optical intraoperative margin imaging, were presented at the American Society of Breast Surgeons 10th Annual Meeting, being held in San Diego, California.

The researchers found that in 48 patients and 55 margins, the technique correctly identified 80% of the pathologically positive/close margins and 67% of the pathologically negative margins.

The optical imaging technique takes advantage of the fact that light has distinct interactions with different biochemical substances and that cancerous and noncancerous cells have different biochemistry, said Quincy Brown, PhD, a postdoctoral researcher in the Department of Biomedical Engineering at Duke University, during a meeting press conference.

Notably, analysis of the margins in the pilot study was not performed during surgery, which is the ultimate goal of the technique. In the study, the technique was used on the excised breast tissue. Because it was used postoperatively, the technique had no influence on clinical decision-making, explained Nimmi Ramanujam, PhD, associate professor of biomedical engineering at Duke, in a press statement.

During the news conference, Dr. Brown said that the technology is not appropriate for breast cancer screening.

"The shallow light depth of the technique is not good for screening for breast cancer but is good for margins," he explained, noting that the "sensing depth" of the light's wavelength was not powerful enough to adequately analyze unexcised tissue.

How It Works

In the study, the researchers evaluated tumor margins using optical intraoperative margin imaging and compared the findings with pathology results. Positive margins were found in 34 of the tumors with standard pathology, 13 of which were clearly positive and 21 of which were close (less than 2 mm) to the margin. Optical intraoperative margin imaging identified 27 of these 34 margins (80%) as positive/close, said the researchers.

Less impressively, the technique only correctly identified 14 of the 21 negative margins (67%).

The mean invasive tumor size was 1.78 cm, and the specimens had up to 3 margins evaluated.

The new technique employs a hand-held fiber-optic imaging probe connected to a computer console. "Our device consists of a broadband light source for illumination, an imaging spectrograph and charged-couple device camera for detection, and an imaging fiber-optic probe to relay light to and from margins of the tumor," write the researchers.

Breast specimens are physically evaluated in a Plexiglass box designed to expose and evaluate the margins.

Optical intraoperative margin imaging captures images of different biochemical substances with varying colors and intensities, and uses mathematical models developed at Duke to characterize the underlying tissue composition in the margins of the tumors.

The imaging has the ability to reveal areas of high cell density and low fat content — these are suspicious of disease, said Dr. Ramanujam. Areas with low cell density and high fat content are expected to be negative for disease, he continued.

The technology is "fast," said Dr. Brown. For instance, the imaging requires about 30 seconds to produce an analysis of an area that is 3 cm × 2 cm, according to the researchers. The speed of the computerized evaluation will allow the technique to be used intraoperatively and could potentially enable surgeons to correct margins as needed during the initial lumpectomy.

In addition to quickly producing an evaluation of tissue margins, the imaging technique is portable and of moderate cost, said Dr. Brown, and does not require any staining of tissue samples, as is the case with standard tumor tissue pathology.

This noninvasive imaging device is expected to undergo clinical trials with the goal of commercialization for surgical applications, according to the press statement.

The researchers have disclosed no relevant financial relationships.

American Society of Breast Surgeons 10th Annual Meeting: Abstracts 10. Presented April 24, 2009.


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