Malignant tumor strongholds and their microscopic spies can’t hide in the thicket of flesh much longer, for surgeons have a new weapon: a device that sheds light on their location. Literally.
“Any state of disease will alter the cells and molecules in our body,” said Dr. Stephen Boppart, a professor of bioengineering at the University of Illinois who invented the device. Every molecule scatters light different ways, he said, “leaving a distinct optical scattering signature.” The new device senses cancer cells’ unique signatures, letting surgeons know which areas around the tumor are cancerous and which are safe to leave alone.
The tissues surrounding a tumor, known as the margin, are a hot spot for cancerous cells. Since the malignant parts of the margin are invisible to the naked eye, surgeons have to use their judgment to determine how much of it to remove. If they abscind too much, the patient loses healthy tissue, too little and the cancer cells that remain could quietly form a new tumor.
Today, surgeons send samples from the margin to the lab, and unfortunately results often come back positive for cancer cells. Breast cancer patients run a 30-50% chance of getting called back to the hospital for repeat surgeries.
Boppart’s team built upon existing imaging techniques, which often require large equipment, and repackaged them into a microscope the size of a flashlight, allowing the device to be used during procedures to guide a surgeon’s hand.
The device works because tumors are much more densely packed than healthy tissue and cancerous cells are organized differently than healthy ones. When certain wavelengths of light are shone on them, cancerous areas light up like cellular cities at night. The technology Boppart used, known as optical coherence tomography (OCT), has successfully identified malignant and healthy tissue in breast tissue samples outside of the body. However, Boppart points out, “it’s more important to look at what’s inside and not removed.”
Surgeons can glide the probe in the tumor cavity and see a cross-sectional map of tissue on a nearby monitor, similar to an ultrasound. OCT, though, offers surgeons a ten- to 100-times greater resolution than ultrasound technology.
The probe has important advantages over other imaging techniques that have been used in cancer surgery patients. One involves labeling the margin with a fluorescent dye that can highlight patches of malignant tissue. But even then there is a chance that the dye won’t label everything. Further, Conor Evans, who researches OCT at Harvard Medical School, emphasized the difficulty in researching contrast dyes and getting them approved by the FDA. OCT doesn’t require a dye to be injected into the patient, which makes it easier to get approved.
Another existing technique—using radio frequency waves—is label-free, but it is slow compared with OCT. With a radio frequency device, the surgeon must point the probe, wait a few minutes to get results, and then repeat the process.
OCT’s instant feedback means surgeons will not have to wait hours or days for results from the histology lab, where tissue samples are typically sent to determine whether they are malignant.
So far, Boppart’s probe can successfully distinguish apart healthy and cancerous tissue with 92% sensitivity and detection. Though it has only been tested on breast tumors, he claims the device will be useful with any sort of solid tumor removal. Boppart now hopes to develop algorithms that will automatically flag for surgeons suspicious areas in the margin.
The new OCT probe is FDA approved and will likely available in 2016. Soon, it may help catch cancer’s rogue microscopic spies in their tracks, helping patients avoid further operations.
Photo credit: Alex Jerez and Stephen Boppart/Beckman Institute for Advanced Science and Technology