Photodynamic therapy uses a light-sensitive drug (a photosensitizer) that is taken up by cells and, after a waiting period, is activated by aiming a specific wavelength of light at the treatment area. The activated drug creates a form of oxygen that kills nearby cells and can damage tumor blood vessels. Because the light must reach the target, PDT is best for cancers and precancers on or just under the skin, or in the lining of organs a light source can reach (via endoscope), such as the esophagus and airways. It is used for actinic keratoses and some skin cancers, Barrett’s esophagus with dysplasia, and certain early or obstructing esophageal and lung cancers.
The photosensitizer is applied to the skin or given intravenously; after a set interval, a laser or other light source is directed at the area (on the skin, or through an endoscope for internal sites). It may be done in a clinic or as a short procedure.
With systemic photosensitizers, the skin and eyes become very sensitive to light for a period, so patients must avoid bright light and sun. Local reactions (redness, swelling, soreness) in the treated area are common and settle over days to weeks.