Photodynamic therapy (PDT)
What is photodynamic therapy (PDT)?
PDT utilises cream and light to kill off superficial basal cell skin cancers or pre-cancers, such as actinic keratoses and Bowen’s disease. It can also be used in cases of moderate to severe acne. In the case of acne, PDT is thought to work by shrinking the skin’s oil glands and killing the bacteria that cause flare ups. Its beneficial action on the skin’s overall texture may assist in repairing acne scarring. PDT is non-invasive, i.e. it does not involve any surgery.
A cream is applied some three hours or so before the light is shone on it. In this time it becomes selectively absorbed by the abnormal cells and is converted into a drug, known as PPIX. When a red light is shone on PPIX, free radicals and singlet oxygen are created and these destroy the targeted cells. Healthy skin is left unharmed in this process. Normally treatment consists of two sessions, one week apart.
What happens during a PDT session?
PDT is administered as an Out Patient procedure and takes up most of the day. The session begins in the morning. Before the Metvix is applied, the area to be treated is thoroughly cleaned and any crust is removed, to aid maximum penetration of the cream. Following application, a dressing is put in place to protect the area from normal light. Usually a period of three hours is needed to ensure optimal absorption and patients can return home if they wish during this time.
In the afternoon, the dressing and any excess cream are removed. The area is then exposed to the red light for around nine minutes.
When treatment is complete, a further dressing will be applied and this must be kept in place for some 36-48 hours to protect the treated area from exposure to daylight. Some blistering or ooze for a few days following treatment is normal but this should be mild.
The skin that has been treated must be kept clean and dry. Patients may have a bath or shower, but should use water only and avoid soap or bath lotion while the area is oozing. Following washing, careful drying by gently patting with a clean towel is advised. Daily application of a moisturising cream, such as Diprobase, is recommended. When there is no ooze, it is not necessary to apply dressings.
Follow-up appointments are usually scheduled for 3 and 12 months following PDT treatment and these are an opportunity for progress to be reviewed and any concerns to be addressed.