Photodynamic therapy uses light and has been used to treat other forms of cancer, mainly in the head and neck.
Researchers at University College London are assessing the use of photodynamic therapy for prostate cancer.
Photodynamic therapy uses a drug based on chlorophyll, which is injected into the bloodstream and makes the whole body sensitive to light. The drug only works when it is activated by special light from a laser. Thin optical fibres are put into the prostate to deliver the laser light. The activated drug then acts to block blood vessels and cause the death of prostate cells (normal cells and cancer cells).
Hopefully, this treatment could offer fewer side effects than current treatments, such as surgery and radiotherapy. It can be done with a 24-hour hospital visit, and if it proves successful, it could be repeated if necessary.
What is photodynamic therapy?
Photodynamic therapy (PDT) can be used as a treatment for many diseases, for example, prostate cancer. It uses a drug called a photosensitiser, activated by light, usually from a laser. The activated drug can kill the cells around the light fibre by producing reactive oxygen species. These are potent forms of oxygen which can either kill cells directly or attack the blood vessels which supply the cells.
In photochemical terms, the photosensitiser changes energy levels, moving from the ground state, which is at low energy, to the singlet state, which is at higher energy level, when it is activated by light from the laser. This singlet state photosensitiser can either lose energy as light (fluorescence) or heat or be converted to an intermediate state known as a triplet state. In this form, it can undergo one of two types of reaction with oxygen. This produced the high-energy oxygen products that cause the photodynamic therapy effect.
Does photodynamic therapy only kill cancer cells?
Photodynamic therapy, like all of the other treatments for prostate cancer, can kill normal cells as well as cancer cells. However, it seems that cancer cells are more sensitive to PDT, and normal cells can recover or be repaired much better than cancer cells. Vascular-targeted photodynamic therapy with Tookad is thought to work on the blood vessels supplying cancer cells more effectively than on normal blood vessels. This is one of the aspects of the treatment that is being investigated in current studies.
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