ORLANDO — Light may soon take a place in the diagnostic and surgical armamentarium for breast cancer.
Researchers at the Technical University of Munich, Germany, 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, Dr. Volker Jacobs said at a meeting on laparoscopy and minimally invasive surgery.
The prototype chosen for study uses a 300-watt 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, said Dr. Jacobs, a research and clinical consultant in obstetrics and gynecology at the university.
This picture isn't optimal for diagnostic evaluation, however, he said in an interview. “We needed a more sophisticated way of viewing the information. So a complex data processing was performed to invert the picture [healthy areas diminish and suspicious areas are highlighted], and then we overlay 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. The paper describes five patients 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 ductoscopy 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. Since the procedure uses only light, there was no need for intravenous administration of any contrast agent.
The paper notes that areas of suspicion reflected distinctly different light values than did 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 open the door to an impressive array of applications for autofluorescent ductoscopy, he said. “It 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.”
Similarly, he said, these color gradations could someday benefit women at high risk of breast cancer. “We might be able to develop this into an early screening procedure for these patients,” Dr. Jacobs said. “This is hypothetical at this stage, but we are convinced it can be done.”
Since the initial feasibility study included only five patients, there weren't enough data to characterize ductal lesions according to imaging color. But Dr. Jacobs hopes to publish a larger case series within a year; this study 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.
This type of interventional ductoscopy is under investigation in Europe. Miniature instruments only 0.8–0.4 mm in diameter are used in the procedures, passing through an additional working channel of the ductoscope.
Instruments include cytology brushes, microforceps, and a titanium basket for grabbing and removing intraductal papillomas. “All of these devices are either already in clinical use or are being investigated in Europe,” Dr. Jacobs said. “But interventional ductoscopy is still an experimental procedure. We do not yet know, for example, if the removal of a papilloma by this means is as effective as the removal by traditional surgery. This needs further evaluation in trials.”
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. Jacobs said.