Surgical Probe Determines Where Tumors End

University of Illinois at Urbana-Champaign Champaign, IL

New tool uses light to image tissue in real time.

An interdisciplinary team of researchers at the University of Illinois has performed a clinical study comparing a new surgical tool that uses light to ensure that surgeons are completely removing cancerous tumors against traditional pathologists’ diagnoses. Their results were positive, and could lead to the tool enabling reliable, real-time guidance for surgeons. The team, led by Stephen Boppart, a professor of electrical and computer engineering and of bioengineering, performed the study on 35 patients with breast cancers.

It can be difficult but crucial for surgeons to determine where a tumor ends. A solid tumor may be easily identifiable, but the margin tissue around the tumor may contain cancerous cells, too. So, excess tissue surrounding the tumor is typically removed, but it’s often unclear whether any cancer cells remain.

“In almost all solid-tumor surgeries, there’s a question of margins,” said Boppart, who also is a medical doctor. “Typically, surgeons will remove the tissue mass that contains the tumor and will send it to the lab. The pathologist will process, section, and stain the tissue, then examine the sections…The diagnosis is made based on subjective interpretation and often other pathologists are consulted. This is what we call the gold standard for diagnosis.”

The new device consists of a handheld probe based on optical coherence tomography (OCT) that uses light for real-time tissue imaging. Cancer cells and normal tissue scatter light differently because they have different microstructural and molecular features, Boppart explained, so OCT gives physicians a way to quantitatively measure the cellular feature of a tumor. Surgeons can pass the OCT wand over a section of tissue and see a video on a screen, with no special chemical stains or lengthy tissue processing required. (See Figure 1)

“In many cases, you can’t tell the difference between cancer cells and normal tissue with the naked eye, but with OCT they’re very different,” said Boppart.

In the clinical study, surgeons treated patients according to the standard surgical procedure, but OCT data were collected from the margin of the tumor cavity and the margin of the removed tissue mass during surgery so that the results could be compared later. The study found that the OCT device analysis identified the differences between normal and cancerous tissue with 92 percent sensitivity and 92 percent specificity. They also found that the way that OCT spotted cancer in the removed tissue was closely correlated with the results from the postoperative pathology reports, which often came days later.

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