Photodynamic therapy (PDT) is a treatment in which a special light-sensitive drug is taken i.v. or by mouth or applied to cancer on the skin as a cream. The drug accumulates extensively in the cancer cells, and minimally in the normal surrounding cells. The cancer is then exposed to intense light of a specific colour causing a reaction with the drug which results in rapid death of the cancer cells. Blood vessels that feed the tumour are also damaged. In some cases, the immune system may be activated into detecting the cancer, and destroying it in other areas of the body (called photoimmunotherapy). There is minimal damage to the healthy cells surrounding the cancer.

Scientists at the University of Oklahoma have achieved apparent cures in a small number of patients who have metastatic melanoma using photoimmunotherapy. There is a potential to also apply this treatment to other cancers.

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