Probe made to determine if all cancer is removed

WASHINGTON, D.C. — Patients emerging from cancer surgery want to know: “Did you get it all?” Now, scientists are developing a pen-like probe to help surgeons better tell when it’s safe to stop cutting, or if stray tumour cells still lurk.

The device is highly experimental, but tests show it uses molecular fingerprints to distinguish between cancerous cells and healthy ones far faster than today’s technology, Texas researchers reported this week.

“That’s really anyone’s worst nightmare, to go through surgery and know there’s a chance” some cancer remains, said assistant chemistry professor Livia Eberlin of the University of Texas at Austin, who is leading the work. “By providing realtime molecular information, we could really improve accuracy.”

Her team aims to begin testing the device during surgeries, starting with breast cancer, early next year.

When surgeons think they’ve removed all of a tumour, they often also remove a thin layer of surrounding tissue, called the margin, to be sure no cancer cells linger at the edge and increase the risk of relapse.

The problem is that such a check takes time, for pathologists to process the tissue and examine it under the microscope. For certain especially tricky tumours, surgeons sometimes pause for a half-hour to more than an hour, the patient still under anesthesia, to await the results. For breast cancer and certain other types, often the answer doesn’t arrive until a few days after surgery, raising the possibility of repeat operations.

In contrast, “our device is able to give an immediate read-out in under a minute,” said UT research engineer Noah Giese.

Cells produce unique sets of small molecules that perform various functions, and thus also act as fingerprints.

Researchers place the penlike device directly onto tissue, press a foot pedal to switch it on, and a tiny amount of water emerges to gently pull molecules from the cells in that spot.

A tube carries the droplet to a machine called a mass spectrometer that identifies molecules by calculating their mass. Software then analyzes whether the resulting fingerprint matches cancer or healthy tissue.

In lab tests of samples that had been taken from 253 patients with lung, ovary, thyroid or breast tumours, the so-called MasSpec Pen was more than 96 per cent accurate in diagnosing cancer, researchers reported in the journal Science Translational Medicine. They also successfully used the pen during a handful of operations on mice.

If it pans out, doctors would have to place the pen on several spots to check an entire wound. Researchers noted it doesn’t appear to harm tissue, meaning pathologists still could doublecheck with standard techniques when human testing begins.