Scientists create better marker for breast cancer

Researchers at the University of California said the new tiny silica microbubbles they have created could also reduce the need for second surgeries and minimise pre-surgical discomfort for patients.

Describing their work in forthcoming issue of the journal MedChemComm, they said the microscopic gas-filled spheres of silica, a porous glass, can pin point the location of early-stage tumours using ultrasound imaging in the operating room.

Generally, the X-rays carried to to locate the tumours reveal calcium deposits associated with breast cancer even in tumours too small to be felt. But surgeons can't use X-rays while operating. Instead, radiologists place guide wires into tumours hours or even the day before surgery.

The wires don't mark depth well and can shift. Patients find them both uncomfortable and unsettling.

As an alternative, the researchers created spheres of silica and filled them with perfluoropentane, a gas that has been used before in short-lived contrast materials for medical imaging. The rigid silica shells help the new material last longer.

"These little gas-filled microbubbles stick to human breast tissue for days and can be seen with ultrasound," said William Trogler, professor chemistry at the university, who led the study.

"If doctors placed them in early stage breast cancer, which is difficult to see during surgery, they could help surgeons remove all of it in the first operation."

In the past few years, radiologists have tried implanting radioactive "seeds" instead of wires to mark tumours, but the seeds last only a few hours and must be inserted with a large-bore needle, which is painful.
The seeds also expose both patient and staff to radiation, can't been imaged in three dimensions and create radioactive medical waste.

At just two micrometers in diameter -- half the width of a strand of spider silk -- the small silica microbubbles can be precisely injected into clusters of abnormal cells using a thin needle, the scientists said.

Radiologists would be able to inject the durable material days before surgery and ultrasound scans can reveal the position of the bubble in three dimensions on the operating table, they said.

"Instead of just using a Geiger-counterlike device to say you're getting closer to the radioactive seed, you could actually see where to carve," said Andrew Kummel, professor of chemistry. The increased precision should help surgeons avoid the need for second surgeries.

"By outlining the tumour more completely in multiple directions, the particles could potentially help surgeons remove non-palpable tumours in a single operation," said Sarah Blair, a surgeon at Moores UCSD Cancer Center.

"They will definitely make the operation more comfortable for patients."