What is Photodynamic Therapy (PDT)?
A cream containing a chemical known as ALA is applied to the area of skin to be treated. This ALA is preferentially absorbed by the abnormal skin cells. When subsequently exposed to the light of a certain wavelength, a reaction takes place between the ALA and the light in the abnormal cells which result in cell death. Normal surrounding cells remain unaffected. This technique is more often used for Actinic Keratoses, however may be used for superficial BCCs on the trunk and limbs NOT on the face.
Is PDT a new Treatment?
PDT is not new, having been successfully used at our premises since 1995 and elsewhere world over. Certainly, technology has improved greatly over time the years.
Is PDT safe?
PDT is an exceptionally safe procedure, with no medically serious complications on record.
What conditions are treated with PDT?
- Surface-based skin cancer
- Superficial BCC
- SCC in situ (Bowens Disease)
- Actinic Keratoses (AK) – individual lesions or over an area of abnormal skin
- Actinic cheilitis (precancerous change on lower lip)
- On sun-damaged skin for rejuvenation
- Miscellaneous – acne, warts and rosacea
What happens on the day of treatment?
- Initially the area to be treated is marked out and the Nurse/Doctor gently curettes (scrapes) the surface of the lesion(s).
- ALA cream is then applied by a nurse and meticulously covered to protect the area from sunlight.
- 3-4 hours later, the patient returns for the light treatment, which takes 10 to 15 minutes.
- During treatment minor pain is experienced which is an indication that the desired reaction is occurring.
- A small percentage of patients experience intense pain and may require local anaesthesia.
- A light dressing is applied to the area after treatment.
What happens after treatment?
- The treated area usually has a mild burning or stinging sensation for the first 24 hours, analgesia is rarely required for this.
- A small percentage of patients do experience more intense pain and require analgesia.
- The treated area becomes red as if sunburned and will usually peel off in a week.
- Occasionally blistering, scabbing may occur. This indicates a stronger reaction and is normal.
Should I avoid sunlight after treatment?
It is essential to stay out of the sun for the remainder of the day of the treatment as the area will be particularly sensitive to sunlight.
How many treatments are required?
For skin cancers, generally, 2 treatments spaced 2 to 4-8 weeks apart are necessary. For any remainder of the conditions, in most cases, a single treatment is adequate.
What medications affect this treatment?
Certain drugs and medications may result in an extra strong reaction. These include
- Some antibiotics such as tetracyclines (doxycycline)
- Antihypertensives e.g. thiazides
- Antifungals e.g. griseofulvin
- Antidiabetic e.g. sulphonylureas
- Antipsychotics e.g. phenothiazine
- As with any treatment, it is important to inform the doctor of all current medications or any current illnesses.
Advantages of PDT
- Safe, with no serious side effects or complications
- Excellent clinical results
- Excellent cosmetic results
- Can be repeated, if required
- Suitable for all skin types
Disadvantages of PDT
- Painful for a small percentage of patients
- Limited by the depth of penetration of both the cream and the light, so that only superficial skin can be treated
- Limited by the inability to assure complete eradication of skin cancer as there is no confirmatory pathology report as part of the treatment
- Only small areas can be treated at the one time (see NL-PDT)
It is critical, therefore, that PDT is only used for the appropriate skin cancer types.