Cancer surgery could soon become more precise and more successful.
Scientists in Australia say they have invented a probe that distinguishes between healthy and cancerous breast tissue.
The optical fiber device could make surgery more precise and help surgeons avoid removing too much healthy tissue, they say.
This new capability also means that a patient may be able to avoid future operations to remove unhealthy tissue left from the initial surgery.
Currently, 15 to 20 percent of patients who undergo breast cancer surgery need an additional procedure to remove residual cancer tissue, the researchers said.
Measuring pH levels
The University of Adelaide researchers call their device — which pinpoints the margin between normal tissue and breast cancer — the Cancer Margin Probe.
This technology breakthrough was unveiled November 30 in Cancer Research, the journal of the American Association for Cancer Research.
Erik P. Schartner, Ph.D., is co-author of the report, and a postdoctoral researcher at the School of Physical Sciences and the ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP) at The University of Adelaide.
He worked in collaboration with the Breast Endocrine & Surgical Oncology Unit at the Royal Adelaide Hospital.
“The probe works by measuring the difference in pH on the tissue surface, which actually correlates really well to whether the tissue is healthy or cancerous,” Schartner told Healthline. “The probe has a pH indicator attached to the tip, which changes the color of the light it emits depending on how acidic or basic the surface is.”
The researchers tested four mastectomy specimens. They included one example of axillary clearance (removal of lymph nodes and surrounding fat) from a patient with recurrent breast cancer, and three other samples of metastatic melanoma (stage 4 skin cancer that has spread to lymph nodes, organs, or other areas).
“We place the probe in contact with the surface for a few seconds, remove it, and perform our measurement, which we then correlate to post-operative pathology to give us an indication of how well our probe compares to existing methods,” said Schartner.
Being more precise
The researchers said contemporary cancer surgery techniques lack precision.
Procedures rely on a surgeon’s experience and judgment to determine how much tissue to remove around the margins of a tumor.
This inexact approach means surgeons often must perform “cavity shaving,” which can lead to removing excessive healthy tissue, Schartner said.
The result is many surgeons are not able to remove the entire tumor during the initial surgery. Follow-up surgery is often needed to remove residual cancer tissue.
Schartner said current surgical techniques generally rely on radiology and pathology before the operation to give the surgeon information.
Surgeons currently have no reliable techniques to identify tissue types during surgery. The main input during surgery, Schartner said, is from an X-ray scanner located in an operating facility.
“This isn't perfect,” Schartner said. “In up to 15 to 20 percent of cases post-operative pathology shows that some of the tumor was missed in the first surgery. This is quite traumatic to the patient and has been shown to have long-term detrimental effects on the patient's outcome.”
Schartner said their probe could reduce the incidence of negative results.
“Our probe gives a real-time indication of whether cancer tissue remains on the surface,” he said. “If so, the surgeon should likely excise more tissue from the cavity.”
Physicians see potential value in the probe.
Dr. LaMar McGinnis, senior medical advisor for the American Cancer Society, said surgical margins are of great importance to surgeons with regard to local recurrence of the primary tumor and diminished overall survival.
“This has been a particular problem in the era of lumpectomy for breast cancer, from both the oncologic and economic perspectives, not to mention the patient’s psychological distress brought on by return to the operating room,” McGinnis told Healthline.
He said margin requirements have been shrinking as multidisciplinary approaches to cancer therapy have become the norm.
“So, any progress toward resolving this issue would be greeted with enthusiasm by all parties. This in vivo approach offers much,” added McGinnis. “This is a preliminary study that requires further investigation, which should be encouraged. Accuracy, sustainability, and the ability to replicate techniques in a variety of clinical settings is always a requirement.”
Dr. Hani Sbitany, assistant professor of surgery in the Division of Plastic and Reconstructive Surgery at the University of California, San Francisco, said the probe is “potentially of huge significance.”
The device would be a crucial improvement over current technology, he told Healthline, because at the moment there is no way to differentiate between healthy and cancerous cells in surgery.
“Currently, most breast tumors are marked prior to surgery with a wire placed through the breast skin and into the area of the breast tumor,” Sbitany said. “This is done with real-time MRI guidance, on which the tumor can be visualized. Then, in surgery, the surgeon can dissect toward the tumor, using the wire as a guide. Once the end of the wire is reached, the surgeon knows that the tumor is in this area, and the necessary amount of tissue is removed, based on size of the tumor on MRI. However, it is difficult to know whether the removed specimen contains all the breast cancer cells.”
With such a tool, Sbitany said the rate of follow-up operations to remove remaining breast cancer cells could drop significantly.
Preparing for more tests
The Cancer Margin Probe needs specific improvement before clinical tests can begin.
The probe’s first set of tissue measurements showed 90 percent specificity, Schartner said. In a small fraction of cases, however, the probe results showed a tumor where the sample tissue location was actually healthy, and vice versa.
“In the next phase of trials, we’re looking to improve the experimental methods we're using to work out exactly what's going on here,” he said, “to identify in what cases the probe shows an incorrect result and what we can do to fix this.”
The researchers knew their probe was effective the first time they tested it.
In the early phases of the project, Schartner and his colleagues experimented with spectroscopy (analysis of emitted light), and autofluorescence (natural emission of light by biological structures) and biomarkers (measurement of disease or infection). These yielded limited success.
“The big moment occurred when we did the first trial with our pH probe and were able to visually pick up the differences in the signal between the tissue types before we even did any data analysis or statistics,” he said. “Having something that gave such a large difference in signal between the two types was fantastic, as we knew this was a much less complex method than we'd tried earlier.”
Schartner and his colleagues are applying for early-stage commercial funding for medical devices available from their university and from the government.
Eventually, he said they hope to collaborate with a large medical instrument company during clinical testing and regulatory phases.
The goal is to begin trials within six months of acquiring funding for the next phase of the work, and to get a device to market within two to three years.
Schartner is optimistic about the probe’s future.
“We're hoping it'll make a big difference to current surgical practices,” he said. “Having a vastly experienced surgeon working on the project from day one meant that we were always pushed toward practical solutions. We think we've developed something that should transition well to clinical applications, and will fill a space where the existing technology isn't up to the task.”