New Techniques Outline Tumors' Location in the Brain

Early trials show promise of scans to help surgeons in the OR, or to track the effect of treatments

Friday, February 13, 2015

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FRIDAY, Feb. 13, 2015 (HealthDay News) -- Brain tumors are notoriously tricky for surgeons, who may leave too much cancerous tissue behind or cut into vital, healthy brain tissue.

However, two new studies describe devices that help surgeons and nonsurgical physicians better understand the outline and location of cancerous tissue in the brain, potentially improving outcomes for patients.

One device, a handheld fiber optic probe, could help surgeons see cancer cells lying at the margins of brain tumors in real time, so they can be removed with more accuracy.

The other device is a PET scan that allows doctors to gauge the size and area of a brain tumor. Seeing the outlines of tumors more accurately might help physicians better assess the benefits of chemotherapy or radiation treatment, the researchers explained.

Both studies came as welcome news to experts.

"We are always happy to see new research that is aimed at directly impacting clinical care," said Tom Halkin, a spokesman for the National Brain Tumor Society.

The studies were published this week in Science Translational Medicine.

In the first study, a team led by Dr. Kevin Petrecca of McGill University in Montreal, turned to a technology called Raman spectroscopy. This scan measures the way molecules scatter light and produces an image that is unique to the object.

"The probe allows you to identify cancer cells that normally a surgeon would think would not be there," explained Petrecca, who is an assistant professor of neurology and neurosurgery.

Directing the probe at the brain during an operation produces an image in real time that helps surgeons spot cancer cells they otherwise might have missed, he said.

When the device was tested on brain tissue from 17 patients with advanced brain cancers, it accurately detected not only the tumor itself, but also individual cancer cells that had invaded surrounding healthy tissue, the researchers report.

"With this tool, the surgeon will know if there are cancer cells present or not. Like all cancer, the more you can remove the better for the patient's survival," Petrecca said.

A larger clinical trial is planned. However, the researchers said it's not yet known when the technique might be available to patients, or how much it might cost.

"As the ability to remove as much cancerous tissue as possible plays a critical role in brain tumor patient care and survival, these results are promising," Halkin said. He agreed that more study is needed to confirm that the technology outperforms current surgical techniques.

The second study was led by Dr. Sriram Venneti, assistant professor of anatomic pathology at the University of Michigan in Ann Arbor. His team used PET scans, along with a radioactive tracer chemical, to image brain tumors by tracking how nutrients were being used in the brain.

"This could help diagnose brain tumors," Venneti said. "It might also be a way of monitoring whether therapies like chemotherapy and radiation are working or not, and it may also be able to detect whether the cancer is aggressive."

In a trial of six patients with a type of deadly brain cancer called glioma, the tracer -- which tracked a nutrient called glutamine -- clearly showed the edges of tumors. It even distinguished fast-growing tumors from those that were inactive and no longer growing, Venneti said.

Focusing the scan on particular types of nutrients is key, he added. Both healthy and cancerous brain tissue use glucose, so standard PET scans (which focus on glucose) have not been able to separate out brain tumors. However, by targeting glutamine -- which cancer cells use a lot of compared to healthy tissue -- the PET scan can now highlight the outlines of a particular tumor.

However, Venneti stressed that the technique is still experimental and more testing is needed before it can become a regular part of cancer diagnosis and care. The cost of the scan is also not yet clear.

People advocating for brain tumor care should also understand, "that this imaging approach would complement, not replace, the current standard of care MRI methods widely used for clinical evaluation of brain tumor patients," Halkin said.

Additional studies, in larger numbers of patients, will be needed to validate the accuracy of using PET imaging to detect brain tumors, for measuring patient responses to treatment, and to define the clinical value and application of this new imaging technique, he added.

SOURCES: Sriram Venneti, M.D., assistant professor, anatomic pathology, University of Michigan, Ann Arbor; Kevin Petrecca, M.D., Ph.D., assistant professor, neurology and neurosurgery, McGill University, Montreal, Canada; Tom Halkin, spokesman, National Brain Tumor Society, Newton, Mass.; Feb. 11, 2015, Science Translational Medicine

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