With its high rate of melanoma, Australia is deeply involved in research into a possible cure, and a new treatment involving a dye called Rose Bengal has seen interesting results, writes Pádraig Collins, in Sydney.
AUSTRALIA HAS the world's highest rate of melanoma, the most serious form of skin cancer, with nearly 10,000 new cases diagnosed each year, so it is not surprising that Australian doctors are leading the world in melanoma research.
With those most at risk of melanoma being people with fair-coloured skin, red or fair hair and blue eyes, there are a lot of cases in Ireland each year too. The most recently available figures show that 360 women and 238 men in Ireland contracted malignant melanoma in 2005.
The traditional treatment is highly invasive - surgery and chemotherapy - but Australian researchers are working on an alternative.
Doctors in the Sydney Melanoma Unit, which is part of the University of Sydney's department of surgery, are pioneering a new, non-invasive, approach to the treatment of melanomas, which involves injecting a dye called Rose Bengal into the tumour.
Rose Bengal, which is named after the dye Bengali women use to signify that they are married, is being used with remarkable success to treat melanomas, and the researchers are hopeful it can be used in other cancers.
Prof John Thompson is leading the investigation on behalf of US pharmaceutical company Provectus. "There were some animal studies done several years ago, and it was found that injection of the substance [ Rose Bengal] into tumours in animals had a selective effect in destroying the tumours but not destroying the surrounding normal tissues," he told The Irish Times.
Human studies began under Thompson in Sydney a year ago, with a phase one clinical trial which involved injecting 20 patients with Rose Bengal and observing the effects. "It was very small doses initially and very dramatic effects were observed," he says.
"You can inject almost anything into tumours, you can inject drain cleaner into tumours and it will kill the tumours, but it also damages the surrounding tissues. The difference with Rose Bengal is that it appears to spare the normal tissues and just kill the tumour cells."
All 20 patients in the first clinical trial were in Australia, and 25 of the 30 so far recruited for the second trial are also in Australia. Eventually the second stage will include 80 patients.
Thompson is encouraged by the results so far. "We are able to use bigger doses of the agent and we are able to treat multiple tumours. For the initial study it was very cautious; just a maximum of three tumours and limited dose of the agent," he says.
"It's not for every patient with melanoma, and that's important to understand. It's only for a small proportion of people with recurrent tumours in accessible places, mainly on or immediately under the skin.
"But when you inject them with the substance it does exactly what it did in the animal studies - the tumours by and large disappear, they just necrose."
Despite the success - almost half the tumours injected with the Rose Bengal treatment disappeared completely, and another 30 per cent either shrank or stopped growing - Thompson is cautious.
"Anything that's a local treatment is never going to be the sort of silver bullet we require. What we require is something that will circulate through the whole body and home in on tumour cells wherever they happen to be.
"It is possible that Rose Bengal might do that, but that, of course, would require high dose intravenous administration and we've got a lot of studies to do before we reach that point," he adds.
Rose Bengal is also being tested on other forms of cancer.
"It looks as though it's fairly non-selective in which tumours it's effective for. Tumour cells are different from ordinary cells and there's something in the coating of the cells which allows Rose Bengal to enter the cells," says Thompson.
"They've looked at a number of other cancers, including breast cancer and, I believe, lung cancer, and it works."
Despite the success with injecting Rose Bengal into melanomas, the treatment will remain a specialist pursuit, rather than something available from every GP.
"I don't think it will ever do that. I don't think it's ever going to be suitable for primary melanoma.
"I think it will always be a specialised technique conducted in cancer centres by oncologists, whether they are surgical oncologists or medical oncologists," notes Thompson.
Provectus wants to expand the testing of Rose Bengal to Europe, but the European Union is currently holding this up.
"We're looking to use it in Europe, but there are very strange regulations which were introduced last year in Europe which mean that it will probably be the middle of next year before we can get permission to use it there," says Thompson.
"[ The EU regulations] have to do with pyrogen testing of the containers in which the substance is placed. As far as we know, nowhere else in the world has those requirements," he claims.
"Every substance is pyrogen tested, all drugs, all things that you inject or even put on patients have to be pyrogen tested and that's routine, but this is some strange regulation that involves testing of the containers in which the agent is held . . . It's delaying the introduction of new agents [ into the EU]," he says.
When the testing of Rose Bengal in Europe is allowed by the EU, Ireland, with a high proportion of people most at risk of melanoma, will likely become part of the study.
What is melanoma?
Melanoma is a cancer in the skin cells that produces melanin. Melanoma tumours are often brown or black moles, but can also be present in normal-looking skin.
Exposure to ultraviolet rays from the sun or from sunbeds can damage the skin and can lead to melanoma.
It usually starts on the skin surface, but, in rare cases, it may develop in other parts of the body such as the eye, mouth, under fingernails or toenails or inside the body.
Having fair-coloured skin, with red or fair hair and blue eyes increases the risk of melanoma.
It can almost always be cured in its early stages, but is likely to spread to other parts of the body if not caught early.
For more information, see www.cancer.ie and www.smu.org.au
The National Cancer helpline number is 1800 200 700.