Photodynamic therapy, or PDT, is a treatment that combines the use of a light-sensitive drug called a photosensitizing agent with a certain type of light, states the National Cancer Institute. When photosensitizers are exposed to a precise wavelength of light, they generate a form of oxygen that destroys adjacent cells.
Each specific photosensitizing agent is actuated by light of a certain wavelength that determines how far into the body it penetrates. A combination of particular photosensitizers and wavelengths is used to treat different parts of the body, according to the National Cancer Institute. PDT treatment is more effective on tumors on the skin or slightly under the skin, on cavities, or on the lining of internal organs. Treatment of larger tumors is ineffective as the light necessary to activate the photosensitizers is unable to penetrate more than 1 centimeter into tissue. PDT cannot be used to treat metastasized cancer.
PDT helps to clear precancerous actinic keratosis on sun-exposed surfaces of the skin and moderate-to-severe acne, states the American Society of Dermatologic Surgery. PDT can also be used to treat several other conditions such as superficial basal cell carcinoma, hidradenitis suppurativa and Bowen’s disease.
The side effects of photodynamic therapy are normally temporary and are in relation to the treated area. They can include stomach pain, painful breathing, coughing, trouble swallowing or shortness of breath. PDT can also cause swelling, pain, burns and scarring in adjacent healthy tissue, notes the National Cancer Institute.