A photosensitising (light activated) drug is first administered to patients followed by irradiation of cancerous tissue with laser light, which converts the drug into a powerful cytotoxic (cell destroying) agent. This therapy is applicable to a wide range of solid tumours, the limiting factor often being access to the tumour to perform the procedure.
Photodynamic Therapy takes advantage of a chemical interaction between light and a light-activated drug (photosensitiser) to start a series of chemical reactions that kill tumours. With modern photosensitisers, certain physiological properties of tumour tissue can be exploited to retain high concentrations of the drug in cancerous tissues only.
Cytoluminescent Therapy (CLT) is a recent development in the field of Photodynamic Therapy that uses a specific extract of chlorophyll A, trade name Photoflora as its photosensitiser. Photoflora can be given to a patient orally and accumulates selectively in tumour sites and is cleared from the skin between 24-48 hours so that sun sensitivity is not a problem as it can be in some other photosensitisers.
Previous photosensitisers required the use of lasers, but Photoflora is a whole body therapy with the use of a specialised light bed to sensitise the agent. The agent used is sensitive to ultrasound as well as to red light, therefore allowing deeper penetration. The therapy can be often repeated as Photfloras abiity to keep photosensitive can last up to 90 days. Advanced tumours are treated slowly to avoid rapid breakdown. This method shows promise but would still be described by medical authorities as experimental and unproven. Due to lack of penetration, its effectiveness is limited to lesions on or close to the surface of the body.
PDT has now an established evidence base whilst CLT is largely untrialled.
Therapeutic properties of light have been known and used for thousands of years. Indian, ancient Egyptian and Chinese civilizations have used light to treat various diseases such as psoriasis, rickets and types of skin cancer.
In Denmark at the end of the nineteenth century, Niels Finsen developed the use of red light to treat smallpox and ultraviolet light to treat tuberculosis. This was the start of modern Light Therapy. Finsen was awarded a Nobel Prize in 1903 for his work. Two German medical students, Oscar Raab and Herman Von Tappeiner went on to further develop this therapy using certain wavelengths.
Photodynamic Therapy is available on the NHS but will not often be offered as an option. If you are interested in considering PDT then you may need to ask for a referral. The charity Killing Cancer (see listing below) can be very helpful in obtaining a referral, if appropriate.