Photodynamic therapy

Photodynamic therapy
Side effects

Photodynamic therapy (PDT) is a medical treatment for some types of cancer. PDT uses a combination of laser light of a specific wavelength, oxygen and a light-sensitive drug to destroy cancer cells.

The light-sensitive drug (the photosensitizing agent) is injected into the bloodstream and is taken up by the cells throughout the body. The drug gathers preferentially in cancer cells, but is not activated until exposed to laser light of the appropriate wavelength. When a laser is shone onto the cancer, the drug is triggered to interact with oxygen and form a transitory substance, known as singlet oxygen, which then destroys the cancer cells.

There is a delay between injection and activation of the drug using the laser light. The laser light used in PDT is focused through a fibre-optic, and is shone for only a few minutes. The doctor holds the fibre-optic very close to the cancer so that the correct amount of light is delivered. This means that PDT causes the minimum amount of damage to normal, healthy cells.

In early-stage disease, the aim of treatment with PDT may be to completely remove and cure the cancer. In advanced disease, however, the goal may be to shrink the cancer in order to alleviate symptoms. In this scenario, PDT cannot cure the cancer.

New, normal cells replace those cells killed by PDT allowing rapid healing to occur post-treatment and avoiding the scarring disfigurement that may occur with other types of tissue removal.

Even patients who have had surgery, radiotherapy or chemotherapy in the past can be treatment safely with PDT.