By Wilson da Silva
SYDNEY – A team of scientists claim they have found a new way of killing cancer tumours without using harmful radiation or poisons.
Professor David Phillips, of London’s Imperial College, says he and his team have developed a “magic bullet” technique that, using only special dyes and harmless light, kills cancers without harming the patient.
Along with University of London colleague Professor Stephen Brown, Phillips has perfected “sensitiser” dyes which are harmless when first injected into people.
Two or three days after injection, the dyes have drained from normal tissue in the body, but stay soaked inside tumour tissue and even in individual cancer cells.
An optical fibre carrying a particular wavelength of red light is then inserted into the body and the tumour illuminated.
This activates the sensitiser dye, releasing a lethal element that reacts with lipids on the surface of tumour cells and ruptures them open, killing the tumour.
“When it absorbs light, the dye becomes excited, releasing singlet oxygen which is lethal to the tumour,” Phillips told Reuters.
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 tumours in mice, rats and rabbits since animal trials began in Britain late last year, Phillips said.
Professor Andrew Kaye of Melbourne University, who has used the experimental technique on patients with brain tumours at the Royal Melbourne Hospital, said it has great promise.
“We’re more advanced (than Phillips’ group) in some areas, not as advanced in others,” Kaye said. “But we’ve treated quite a lot of patients with brain tumours.”
In Britain, the Phillips’ dyes, developed over the past eight years, have successfully killed tumours in the pancreas of animals, a cancer that is not surgically operable at present.
“It destroyed pancreas tumours totally,” Phillips said. “Some normal tissue was also killed, but some normal tissue was also regenerated.” He said the technique would likely be applied on tumours in the bladder, colon, breast, brain and surface tissue tumours, but not in lung cancer.
Clinical trials on humans have now begun in Britain and results are expected around mid-1993, Phillips said.
These would show the validity of the process, said Dr Ian Forbes of Queen Elizabeth Hospital in Adelaide.
“I was involved in the research for 10 years,” he said. “I think it needs a lot of development and needs the human trials to see if the animal experiments hold true. Whether it works in humans is another case.”
Phillips’ research, funded by a British cancer charity, has not been patented in the hope it will be brought into commercial application quickly.
“We’d like to see these things get into the clinics as soon as possible,” he said. “The sensitisers (dyes) are not expensive to make, but realistically they are another three years away (from medical application).”
The technique is on the leading edge of the little-known branch of science, photochemistry. “It’s undergone somewhat of a resurrection in the last 10 years. It’s been discovered, forgotten and rediscovered a few times,” he said.
Using light in medical treatment has been around since the 1880s, when physician Neils Finsen cured winter sores on the faces of tuberculosis sufferers by using filtered light.
