ORLANDO — Light may soon take a place in the diagnostic and surgical armamentarium for breast cancer.
Researchers at the Technical University of Munich have developed and are currently evaluating the world's first autofluorescence ductoscope, which has the potential to diagnose the earliest forms of intraductal breast cancer and guide surgical treatment.
The instrument combines an autofluorescence light source and camera already approved in Europe for diagnostic bronchoscopy with a 1.3-mm diameter ductoscope. Like autofluorescence bronchoscopy, it operates on the principle that healthy and dysplastic tissues reflect different percentages of light, Dr. Volker R. Jacobs said at a meeting on laparoscopy and minimally invasive surgery.
Light-induced fluorescence bronchoscopy has been used for several years to identify early lung lesions: A helium cadmium blue laser stimulates the lining of the bronchi to autofluoresce in a range of colors. Normal, healthy tissue is shown as being bright green, and suspicious tissue looks reddish-brown. A summary of studies with this technique concluded that it can increase the detection rate of premalignant lesions by up to six times, compared with conventional, white-light bronchoscopy (Lung Cancer 2004;45[suppl. 2]:S29–37).
In 2003, Dr. Jacobs, a research and clinical consultant in obstetrics and gynecology at the university, and Dr. Stefan Paepke began investigating the scientific and clinical potential of autofluorescence ductoscopy for use in small-lumen endoscopy.
The prototype chosen for study uses a 300-W xenon lamp that emits white light; a foot switch adds a blue filter to change it to a fluorescent excitation light. Under this spectrum, healthy tissue shines brightly, reflecting 100% of the light, while dysplastic tissue reflects a reduced amount, or even none, and fades into blackness. However, this picture isn't optimal for diagnostic evaluation, Dr. Jacobs said in an interview. So the investigators inverted the picture so that healthy areas diminish and suspicious areas are highlighted, then overlaid it with an image from the red-violet spectrum to improve detection of potential lesions. In this final image, suspicious areas and potential intraductal lesions appear blue-violet.
The journal Clinical Breast Cancer has accepted Dr. Jacobs' technical feasibility study for publication. In the paper, he describes five patients who were examined intraoperatively with this technique. All had either histologically confirmed ductal carcinoma in situ or papilloma that had been discovered with other imaging methods or fine-needle biopsies.
Diagnostic and autofluorescence ductoscopies were performed before segment or duct excision or lumpectomy. The additional time required for the ductoscopy was minimal, ranging from 5 to 15 minutes, and there were no associated complications. There was no need for intravenous administration of any contrast agent because the procedure uses only light.
The paper notes that areas of suspicion reflected light values distinctly different from those of normal tissue. “The degree of blue-violet color appears to be proportional to the degree of alteration in this tissue, just as it is in bronchoscopy,” Dr. Jacobs said at the meeting sponsored by the Society of Laparoendoscopic Surgeons. “The more light we see, the more dysplastic the tissue should be.”
This observation, if confirmed in prospective trials, could “lead us to be able to intraoperatively differentiate between benign and nonbenign lesions, and maybe even to have semiquantitative visual differentiation that would allow us to make some instant conclusions about the lesion. This could really improve the diagnostic value of the procedure and might even allow earlier therapeutic intervention,” said Dr. Jacobs. “We might also be able to develop this into an early screening procedure for [high-risk] patients.”
Dr. Jacobs hopes to publish a larger case series that will include more data on color gradations, and compare the autofluorescent imaging to standard imaging techniques.
The most immediate application of autofluorescent ductal imaging would probably be surgical, he said. “If we could take a biopsy under autofluorescent visualization, we might be able to use the color as a guide to getting clear margins. This might cut down on the number of R1 resections, and also reduce the need for consecutive operations to ensure clear tumor margins.”
In fact, Dr. Jacobs said, autofluorescent diagnostic ductoscopy would combine very well with interventional ductoscopy. The color gradations would guide the surgeon to the suspicious area, which could be treated endoscopically.
Neither investigator claims a financial interest in either the procedure or the unit.
Dr. Volker R. Jacobs is shown with a display of images obtained on his prototype autofluorescent ductoscopy. Courtesy Dr. Volker R. Jacobs