Photodynamic therapy (PDT) destroys cancer cells with a drug called a photosensitizer, which makes cells sensitive to light. For non-melanoma skin cancer, PDT may be used:
- as a standard treatment for precancerous conditions (Bowen’s disease and actinic keratosis) and superficial basal cell carcinoma
- in place of surgery to treat:
- large skin cancers that are not too deep
- several skin cancers in one area
- areas of skin cancer directly over a bone
PDT is done in 2 stages:
- The crust and scales may be removed from the area and a photosensitizer cream is applied to the skin. It is left on the skin for a specific period of time (3–6 hours) so that it penetrates the skin. Sometimes the photosensitizer may be injected into the body or given in tablet form. Over time, the photosensitizer leaves most normal cells, but stays in cancer cells.
- Once the photosensitizer is absorbed by the cancer cells, the area is exposed to a low-intensity laser light. The light treatment lasts up to 45 minutes, depending on the light source. The photosensitizer in the cancer cells absorbs the light and a chemical reaction occurs that kills the cancer cells without affecting most normal cells.
PDT only destroys cancer cells near the surface of the skin that can be reached by the light. PDT cannot be used for basal cell carcinoma that has spread into deeper layers or for invasive squamous cell carcinoma because the risk of recurrence is too high.
Usually only one treatment of PDT is needed, but 2–3 more treatments may be given for a thicker skin cancer.
People treated with PDT may need close follow-up after treatment to check if the cancer has returned.
After treatment, people need to take special precautions because the photosensitizer makes the skin sensitive to light. A dressing is put on the area to cover and protect it from light. This is usually kept on for about 36 hours.
PDT may not be available at all treatment centres.
See a list of questions to ask your doctor about photodynamic therapy.