June 13, 1992

Article at Toronto Star

Method ‘safer, cheaper’ than radiation

Photodynamic therapy uses special dyes and beams of light to kill cancers

By WILSON da SILVA
Reuters

SYDNEY, Australia – Blasting cancer tumors with radiation or injecting them with poisons can kill them, but it can also end up killing the patient.

But Professor David Phillips of London’s Imperial College says he and his team of researchers have developed a “magic bullet” technique that uses special dyes and beams of light to kill cancers without harming the patient.

This is how it works: First, harmless “sensitizer” dyes are injected into cancer patients. Two or three days after injection, the dyes have soaked the inside of the tumor and even individual cancer cells.

Next, an optical fibre carrying a particular wavelength of red light is then inserted into the body and the tumor is illuminated.

This activates the sensitizer dye, releasing a lethal element that reacts with lipids on the surface of tumor cells and ruptures them, killing the tumor.

Known as “photodynamic therapy,” it is a technique which scientists around the world are working to perfect.

It is safer, cleaner, quicker and cheaper than using radiation and has applications in dentistry, unblocking clogged arteries and in rapid diagnosis.

It is still experimental but has successfully destroyed tumors in mice, rats and rabbits since animal trials began in Britain late last year, Phillips said.

Based on his research, Phillips said the technique would probably be applied to tumors in the bladder, colon, breast, brain and surface tissue, but not in lung cancer.

Professor Andrew Kaye of Melbourne University has for the past few years used the experimental technique with his own concoction of dyes on patients with brain tumours at the Royal Melbourne Hospital. He said it has great promise.

“We’re more advanced (than Phillips’ group) in some areas, not as advanced in others,” he said by telephone from Melbourne. “But we’ve treated quite a lot of patients with brain tumors.”

In Britain, the Phillips dyes, developed over the past eight years, have successfully killed tumors in the pancreas of animals.

“It destroyed pancreas tumors totally,” Phillips said. “Some normal tissue was also killed but some normal tissue was also regenerated.”

Clinical trials on humans have now begun in Britain and results are expected around mid-1993, Phillips said.