Photodynamic Therapy (PDT)
Photodynamic therapy (PDT) is a technique that is used to treat certain types of skin cancers such as superficial Basal cell carcinoma and Actinic Keratosis (AKs) which are areas of sun damaged skin (pre-cancerous) that might become cancer in the future.
How does photodynamic therapy work?
PDT uses a light-sensitive chemical called a photosensitiser. This photosensitiser is not active when it is applied to the skin without light. However, when red light or daylight then shines onto the skin where the photosensitiser was applied, the photosensitiser is activated. This causes changes in the oxygen molecules (oxidisation) in abnormal skin cells. These “excited” oxygen molecules kill the abnormal cells. Only the area of skin exposed to both the photosensitiser and to the light will be affected and inflamed. After the inflammation clears, the sun damaged skin will either be cured or improve.
What does photodynamic therapy for skin lesions involve?
There are 2 ways to provide PDT treatment – the “conventional” PDT and the “daylight” PDT.
the first step is to apply a cream or gel containing the photosensitiser to the treatment area. If necessary, any loose scales or crusts are removed from the skin first. A dressing is then applied over the cream and you will be asked to return in about 3 hours. This wait is to allow the photosensitiser to be absorbed and to be converted into the active chemical by the skin. The cream or gel is then wiped off and the area cleaned. A bright light is then shone onto the treatment area for approximately 10 to 15 minutes (the exact time will be decided by your doctor or nurse depending on the light source). After the treatment has been completed, a dressing will be applied for at least 24 hours, to prevent any further exposure to light.
It is used only if the conditions are suitable for staying comfortably outdoors for 2 hours (with temperatures > 10 ºC). Sunscreen is applied to the whole area that needs to be treated. If necessary, any loose scale or crusts are removed. A cream or gel containing the photosensitiser is applied to the area to be treated. You should then go outside within 30 minutes of the cream or gel application. You should stay outdoors for 2 continuous hours in full daylight. The cream or gel is then removed and the area cleaned. A dressing is then applied to cover the treatment area from the sun for the rest of the day to reduce inflammation. Use of gentle cleansers and moisturizers is recommended for the following week to avoid crusting.
Immediately after the treatment:
- Keep the dressing in place for at least 24 hours, you will need to keep the area clean and dry for this period
- You can take paracetamol by mouth post treatment if discomfort or pain is experienced
After 24 hours
- No dressing or specific skin care required
- Daily, gentle washing with a delicate cleanser and regular use of Lynton Light Soothe to keep the skin moisturised.
Following your first treatment, the treatment may be repeated approximately 1 week later depending on the type of lesion. Usually the specialist will review at 3 months, and advise about any further treatment.
Contraindications - 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, as you would be producing the same photosensitiser used in PDT in your blood, skin and other parts of the body).
Risks & Side Effects
The short-term side effects of phototherapy include:
- Pain (common). When the red light is shone onto the skin, the treated area may hurt. If it is too uncomfortable, your doctor or nurse may suggest pausing treatment for a while, or a local anaesthetic injection may be recommended. After completion of treatment, discomfort and itching may last for a few days, and may require pain-killers.
- Inflammation (common). The treated area may initially become pink, red and puffy, and may crust or ooze a little: this is a normal reaction. It settles within a few days.
- Blistering and ulceration (uncommon). The treated area may occasionally blister or open up (ulcerate) to develop a raw surface.
- Bruising (uncommon). The treated area may occasionally show some bruising.
- Changes in hair growth (uncommon). The treated area may occasionally show increased or loss of hair.
- Dermatitis and contact allergy (uncommon). The treated area may occasionally show signs of dermatitis reaction to the cream or gel applied.
- Infection (uncommon). If the treated area becomes red, swollen and painful, an infection may have developed, and you should contact your doctor.
Potential long-term/permanent side effects of phototherapy include:
- Scarring (uncommon). There may be some scarring after PDT.
- Colour change (uncommon). 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.