The best way to cure most cases of cancer is to surgically remove the tumor. The Achilles heel of this approach, however, is that the surgeon may fail to extract the entire tumor, leading to a local recurrence.
With a new technique, researchers at the University of Pennsylvania have established a new strategy to help surgeons see the entire tumor in the patient, increasing the likelihood of a positive outcome. This approach relies on an injectable dye that accumulates in cancerous tissues much more so than normal tissues. When the surgeon shines an infrared light on the cancer, it glows, allowing the surgeon to remove the entire malignancy.
“Surgeons have had two things that tell where a cancer is during surgery: their eyes and their hands,” said David Holt, first author on the study and professor of surgery in Penn’s School of Veterinary Medicine. “This technique is offering surgeons another tool, to light tumors up during surgery.”
Holt collaborated with a team from Penn’s Perelman School of Medicine led by Sunil Singhal, an assistant professor of surgery. Their paper appears in the journal PLOS ONE.
Between 20 and 50 percent of cancer patients who undergo surgery end up experiencing a local recurrence of their cancer, indicating that the surgeon failed to extract all of the diseased tissue from the site. Identifying the margins of a tumor can be difficult to do during a procedure, and typically surgeons have had to do this by simply looking at the tumor and feeling for differences with their fingers.
Seeking an alternative, Holt, Singhal and colleagues turned to near-infrared, or NIR, imaging. They chose to test the only Food and Drug Administration-approved contrast agent for NIR, a dye called indocyanine green, or ICG, that fluoresces a bright green under NIR light. ICG concentrates in tumor tissue more than normal tissue because the blood vessels of tumors have so-called “leaky” walls from growing quickly.
“Since 1958 when ICG was initially FDA approved, it has been used to examine tissue perfusion and clearance studies,” Singhal said. “However, our group has been experimenting with new strategies to use ICG to solve a classic problem in surgical oncology: preventing local recurrences. Our work uses an old dye in a new way.”