SAN DIEGO—Eben Rosenthal, MD, medical director of the Stanford Cancer Center, described a case involving a lesion in the oral cavity. It was resected, but there was a surprise: a separate lesion, with a focus of less than 3 mm of tumor. The lesion was discovered only because the Stanford surgeons were using a fluorescent tag attached to an anti-epithelial growth factor antibody that homes in on tumors. The fluorescent dye lit up the satellite lesion, which, after testing, was found to be pathologically positive for tumor.
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March 2020“We wouldn’t have even known to look for it,” he said.
The use of fluorescent light to see through normal tissues down to head and neck tumors is showing promise as a way of guiding surgeons and improving margins and outcomes—and occasionally discovering other tumors that weren’t even anticipated, Dr. Rosenthal said here during a panel discussion at the Triological Combined Sections Meeting.
How It Works
Detection of tumor close to the surgical margin on resected specimens is a key advantage of fluorescent light technology, Dr. Rosenthal said. The approach is based on the passage of light through normal tissue. The tumor glows bright from the contrast media. The intensity of light that can be seen shining through depends on the depth of the normal tissue on the deep surface of the surgical specimen.
“The deeper the tumor is from the cut surface of the specimen, you see less fluorescent light,” he said.
The approach doesn’t provide exact distances and depths of the tumor, but in a trial of more than 20 patients, researchers found a high correlation between fluorescence intensity and tumor location, with sensitivities and specificities greater than 89% (Cancer Res. 2018;78:5144-5154). The main goal is to find the “sentinel margin,” or margins, the area of the specimen where the tumor is closest to the cut surface (the smallest margin) and, therefore, most likely to be a close or positive margin. Then surgeons assess the depth of that one area of the specimen on frozen section to ensure the margins are clear, he said.
“You can translate that to where you’re going to sample, where you’re going to take your frozen section,” Dr. Rosenthal said.
Reducing Positive Margins
The field could use new ways to reduce the rate of positive margins, which has been flat over the past 20 years. Dr. Rosenthal noted that this is particularly true for oral cavity cancer, which has one of the higher overall positive-margin rates, according to data from the National Cancer Database. Many labs are working on perfecting the technology, but it is still several years from approval, he said.
“The impact of this technology is very high,” Dr. Rosenthal said. “It’s going to be probably another five years before these agents are commercially available—but hopefully sooner.”