Photodynamic therapy (PDT) is a technique that was invented to treat skin cancers and sun-damaged skin, which might one day turn cancerous (pre- cancers). In PDT, a special light activates a cream, which was applied to the lesion (affected area of skin). This treatment kills the abnormal cells in the skin.
Photodynamic therapy is an exciting and innovative non-surgical treatment for selected superficial skin cancers, avoiding the scar and potential problems of traditional surgery.
It involves the application of a photosensitising cream for three hours to the tumour site. A specialised light is then applied for about ten minutes, which activates the absorbed chemical to create reactions that destroys tumour cells. If used in the correct circumstances, the cure rate is high, without the scarring associated with surgery.
Please discuss the possibility of photodynamic therapy with your dermatologist to determine whether photodynamic therapy would be of benefit.
How does photodynamic therapy work?
PDT involves the use of a light-sensitive chemical (called a photosensitiser). This photosensitiser is, by itself, inactive.
When light of a certain wavelength (usually red light) shines onto skin to which the photosensitiser was applied before, the photosensitiser is activated. This causes changes in the oxygen molecules within the sun-damaged skin cells. These “excited” oxygen molecules kill the abnormal cells. Only the area of skin exposed to the light source will be affected and inflamed. After the inflammation clears, it will be cured in most cases.
What skin conditions can be treated with photodynamic therapy?
PDT can be used to treat various skin conditions including:
- Superficial multifocal basal cell carcinomas
- Squamous Cell Carcinoma in situ – aka Bowen’s disease
What does photodynamic therapy for skin lesions involve?
PDT is an outpatient procedure. It takes several hours to complete. The first step is to apply a cream containing the photosensitiser to the area that needs to be treated. If necessary, any loose scale or crusts are removed first. A dressing is then applied over the cream and you will be asked to return in about 3 hours.
For Daylight full face PDT we generally recommend that you remain in the waiting room for this time as it is very hard to get an appropriate cover for a full face (short of some type of modified balaclava), but for small, discrete areas of treatment that can be covered, it is possible for you to go away for the three hours and then return for treatment.
This wait is to allow the photosensitiser to be absorbed and to convert into the active chemical by the skin. The cream is then wiped off and the area cleaned. When you return there are two options for activating the cream – either using a bright coloured light is then shone onto the treatment area for approximately 8-10 minutes (the precise time will be determined by your doctor or nurse depending on the light source). This technique is called “redlight pdt”.
In some cases, when carefully selected, daylight – such as sitting in the shade under a tree for 10-30 mins will also work. This second technique is called “Daylight PDT”. After the treatment has been completed, a dressing will be applied for a minimum of 2 days, to prevent any further exposure to light. It is very important that you protect the treatment area for at least another 2 days and not expose the area to strong light.
How should the treated area be cared for?
It is usually advised that, after the dressing has been removed, you can wash, bathe or shower as usual. Do not rub the treated area, but gently pat it dry. Within a few days, a scab will form, and healing will take several weeks (depending on which part of the body was treated).
Care must be taken not to scratch the area or accidentally dislodge the scab during the healing process. The use of a suitable sunscreen (SPF 30) following the procedure, especially during outdoor activities, is essential.
What reasons might prevent you having photodynamic therapy?
PDT is not recommended if you are pregnant. The PDT cream may contain peanut oil, so tell your doctor and nurse if you are allergic to peanuts.
PDT is not recommended if you have porphyria (a light-sensitive disorder, where the patient is producing the same photosensitiser used in PDT and is present in the blood, skin and other tissues of the body).
Do I need to avoid anything whilst having photodynamic therapy?
Care should be taken not to get the dressing wet when bathing or showering. It is advisable to avoid swimming until the treated area is fully healed.
What are the potential side effects of photodynamic therapy?
The short-term side effects of phototherapy include:
Pain. When the red light is shone onto the skin, the treated area may hurt. If it is too uncomfortable, we generally suspend the treatment for a few minutes. Cold air from our Zimmer chiller will also help. After completion of treatment, discomfort and itching may last for a few days and may require pain-killers.
Inflammation. The treated area may initially become pink and puffy, and may ooze a little: this is a normal reaction. It settles within a few days. It is similar to a sunburn reaction.
Blistering and ulceration. The treated area may occasionally blister or ulcerate.
Infection. If the treated area becomes red, swollen and painful, an infection may have developed, and you should contact your doctor. Potential long-term side effects of phototherapy include:
Scarring. There may be some scarring after PDT.
Colour change. The skin may become darker or paler after PDT.
Treatment may not be effective, or the condition may come back again. If this happens, you may be offered further PDT, or an alternative type of treatment may be recommended.
Top sun safety tips
Protect your skin with clothing, and don’t forget to wear a hat that protects your face, neck and ears, and a pair of UV protective sunglasses.
Spend time in the shade between 10am and 3pm when it’s sunny. Step out of the sun before your skin has a chance to redden or burn. Keep babies and young children out of direct sunlight.
When choosing a sunscreen look for a high protection 39; SPF (SPF 30 or more) to protect against UVB, and the UVA circle logo and/or 4 or 5 UVA stars to protect against UVA. Apply plenty of sunscreen 15 to 30 minutes before going out in the sun, and reapply every two hours and straight after swimming and towel-drying.