Photodynamic therapy Photodynamic therapy is being increasingly used for sun damaged skin, pre- malignant and superficial skin cancer.

How does it work in the skin?

PDT utilisesphotosensitising agents, oxygen and light to create a photochemical reaction that preferentially destroys pre- malignant and malignant skin cells. A photosensitising cream is applied for a few hours prior to the procedure. This cream concentrates in the abnormal cells and becomes active when light of a certain wavelength is directed at the area where the abnormal cells are.The photodynamic reaction between the photosensitising agent, the light and oxygen kills the abnormal/ malignant cells.

What will prompt my dermatologist to suggest this treatment?

If there are large areas of sun damaged and pre-malignant skin change eg. on the scalp. PDT can treat these areas and prevent the development of subsequent skin cancer. Some areas of skin (for example the chest) can scar more than others. A large area of superficial skin cancer in this area can be treated effectively with PDT, minimising the risk of subsequent scarring. Again the anterior tibial area (skin over the shin) is very thin and can be difficult to operate on and has poor healing. Larger areas of superficial skin cancer or pre-malignant change can be treated successfully here with PDT. The risk of poor healing and possible ulceration is much reduced.

What can I expect when having this treatment?

On the day of treatment the area will be carefully examined by the practitioner. The lesion in question may be scraped (to increase drug absorption) and a margin of skin is marked around. The photosensitising cream is applied and then covered with an opaque dressing. You will then asked to wait for 3- 6 hrs to allow the cream to absorb into the relevant cells. On your return the light is shone directly for several minutes onto the area being treated. During this time many patients feel some discomfort, possibly burning and stinging. A cool spray may be applied for this.

After treatment a dressing is applied. The skin will remain photosensitive for 24hrs, after which the skin may crust and bleed. Skin care advice is given. The 2nd cycle of treatment is given 7 to 10 days afterwards. It may take several weeks for the skin to return to normal.

Should all skin cancers be treated this way?

Absolutely not. The success of this treatment depends very much on careful selection of suitable cases. Deeper and infiltrative non-melanoma skin cancers for example are not suitable for this modality of treatment.