Fluorescent Probe Helps Surgeons Find Ovarian Cancer Cells ► NCI Cancer Bulletin for September 20, 2011 - National Cancer Institute

NCI Cancer Bulletin for September 20, 2011 - National Cancer Institute: Fluorescent Probe Helps Surgeons Find Ovarian Cancer Cells

In a proof-of-concept study, a fluorescent probe designed to bind to epithelial ovarian cancer cells was used safely to visualize small deposits of cancer in the abdominal cavity during surgery, thus helping the surgeon remove the cells. The target of the probe, called folate receptor-alpha, is found in 90 to 95 percent of ovarian cancers but not in normal tissue. The study, the first in of its kind in humans, was led by Dr. Gooitzen M. van Dam of the University of Groningen in the Netherlands and published online September 18 in Nature Medicine.

Ovarian cancer often spreads widely throughout the abdominal cavity, and small deposits of cancer can be difficult to see with the naked eye or detect during surgery. To improve the visualization of tumor cells and allow surgeons to remove more tumor tissue, the researchers tested the imaging agent, which consists of folate linked to a compound (fluorescein isothiocyanate) that glows green under fluorescent light.

The researchers injected 10 women with the probe before surgery. During surgery, the surgeon performed a standard inspection of the abdominal cavity for tumor tissue; the researchers then captured and examined fluorescent images with a three-camera system that did not interfere with the surgical procedure. After the surgeon removed all suspected tumor tissue identified by eye and by the fluorescent probe, the researchers captured a second set of fluorescent images to look for remaining tumor cells. The surgeon then took biopsy specimens of remaining fluorescent tissue to make sure the probe did not give false-positive results (that is, did not mark normal tissue as tumor tissue).

Nine of the patients had tumors that expressed folate receptor-alpha, and the researchers detected fluorescence in tumor tissue in all of these patients during surgery. No fluorescence was seen in adjacent normal tissue. “Real-time image-guided excision of fluorescent tumor deposits [less than 1 mm in diameter] was feasible, and all fluorescent tissue was confirmed to be malignant,” wrote the authors. One woman’s tumor did not express folate receptor-alpha, and the camera system could not detect the tumor cells in her abdomen.

“The use of targeted fluorescent agents could provide a paradigm shift in surgical imaging,” stated the authors, potentially improving the outcomes for patients after surgery by allowing for more thorough removal of tumor tissue. Large studies are needed to confirm these results and determine whether use of the probe can improve diagnosis and surgical treatment, Dr. van Dam and his colleagues concluded.

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