SUN worshippers could soon be slapping on a cream that screens them for skin
cancer. Developed in Scotland, the cream makes tumour cells glow, allowing them
to be spotted by a very sensitive camera.
Australians have a 70 per cent chance of developing skin cancer in their
lifetime, and even the sun-starved British have a 15 per cent chance. The new
test, which was devised by a dermatologist at Ninewells Hospital in Dundee and
physicists from the universities of Glasgow and St Andrews, will make it easier
to catch skin cancer at an early, treatable stage.
The cream contains a compound called 5-aminolaevulinic acid (ALA), which
accumulates in cancer cells and is converted to a fluorescent chemical called
protoporphyrine IX. So while collagen in skin glows a healthy green in
ultraviolet light, cancer cells containing protoporphyrine IX glow red. Because
the fluorescence is too faint to see with the naked eye, the team has also
developed a sensitive camera that鈥檚 cheap enough for screening.
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Protoporphyrine IX is a photosensitiser, making people burn at the slightest
exposure to sunlight, says Miles Padgett, a physicist at Glasgow. However,
unlike other photosensitisers used to detect cancer, which stay in the body for
several weeks, forcing patients to avoid direct sunlight, ALA and
protoporphyrine IX are cleared from the body within a day.
The camera uses a microchip-based charge coupled device (CCD) sensor to scan
different colours, so the team can pick up the telltale red light from cancer
cells. So far the team have built two prototype cameras and are working on a
third version with a much higher resolution. At present they can detect tumours
just a millimetre across but they hope to be able to pick up individual cancer
cells.
Tony Chu, head of dermatology at Imperial College, London, and a consultant
at the Hammersmith Hospital, believes the technique could work. But he says the
cost of equipment makes it impractical for widespread screening. Ferguson
agrees, but says that, at under 拢10 000, the system is cheap enough to
screen high-risk groups.
Ultimately, Ferguson and Padgett would like to see ALA being used to treat
tumours using what鈥檚 known as photodynamic therapy: when cells contain high
levels of photosensitisers, shining light at them releases enough oxygen free
radicals to kill the cells.