Photodynamic therapy (PDT) is a treatment that uses a light-sensitive drug and a laser or light source to destroy cancer cells.
The light-sensitive drug is sometimes called the photosensitising agent. It is a drug that makes cells more sensitive to light. This is called photosensitivity.
The drug is attracted to the cancer cells. It does not become active until it is exposed to a particular type of light. When the light is directed at the area of the cancer, the drug is activated and the cancer cells are destroyed. Some healthy, normal cells in the body will also be affected by PDT, but these cells will usually heal after the treatment.