The Lamp that Kills Cancer Cells
Like A Low Cost Laser
by John Newell
Photodynamic therapy ( PDT ) is not a new idea. But it has taken five years' work by Dr. Colin Whitehurst of the Paterson Cancer Research Institute in Manchester to find a way to make PDT widely available. Dr. Whitehurst says: "This lamp treatment is part of a two pronged attack on cancer. A light-sensitive cream or paste is applied to the cancer and is absorbed by it. Then a light source producing light of special qualities, my lamp, is used to irradiate the cancer that has been coated with the cream. And within a few weeks the cancer has gone."
Two or three different chemicals have been discovered that are readily absorbed by living cells and are harmless until intense light is shone on them. Then they break down and release deadly cell-killing poisons such as free oxygen radicals which are so reactive that they react with, and break down, vital structures in the cells, tearing them to pieces and destroying the cells. Among the photoactivated chemicals are those which are to some extent selectively absorbed by cancer cells. Research has focused on finding ways to deliver these chemicals selectively to cancer cells and to concentrate light upon them so as to kill the cancer cells without damaging normal cells.
Colin Whitehurst explains: "The light, which has to be tuned to a specific wavelength, which is critical, kills the cancer cells but does not harm the normal cells surrounding them. This allows the body to regenerate healthy tissue to fill the gap that was once occupied by the turnour. So at the end of the treatment there's no scarring, no ulceration, you'd never know the cancer had been there in the first place."
So far the lamp has been used in PDT in hospitals in Leeds and Glasgow to treat more than 150 patients, including some affected by the scarring skin disease called Bowens disease as well as two of the most common forms of skin cancer. Like laser-based PDT, it is not effective against melanoma, the most deadly form of skin cancer.
"Results from those first two or three trials (says Dr. Whitehurst) have been very promising, the doctors are well pleased with the results and the ease of operation . After one treatment, twelve months later more than 90% of had been eliminated. And because, unlike conventional cancer chemotherapy, the cancers do not build up resistance to the treatment, tumours that were not killed can be treated with the same effectiveness as with the first treatment. So there is no excuse for failing to destroy these cancers."
"We are planning further trials against breast, ovarian, gullet and bowel cancers and against some non-cancer diseases such as the skin disease psoriasis. That is in the pipeline now. The use of PDT has been held back by the cost of the lasers required, around úl00,000 a piece plus expensive servicing. My light source costs about one-twentieth of that, and should allow a lot more people to benefit."
The lamp has been patented and medical equipment companies are now negotiating to manufacture on a large scale for use in hospitals worldwide. Dr. Gordon McVie, director-general of the UK Cancer Research Campaign who supported the development of the Paterson Lamp, says the lamp should be in production by the end of the year.
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