Photodynamic therapy (PDT) is a non-invasive treatment for skin lesions such as actinic keratoses, basal cell carcinoma and Bowen's disease (squamous cell carcinoma in-situ). A photosensitising cream is applied to the affected area and then exposed to an activating red light (635 nm). Crusting and redness of treated lesions are expected and resolve over 1-2 weeks, revealing smoother, healthier skin.
What is photodynamic therapy (PDT)?
Photodynamic therapy involves the application of a light-sensitive (photosensitiser) cream to the affected area of your skin. The photosensitiser is activated when exposed to specific wavelengths of light. A chemical reaction takes place depriving the affected tissue of oxygen and this ultimately causes the destruction of abnormal skin cells. Over time the damaged tissue crusts and sheds along with the skin’s natural turnover cycle.
Conventional PDT can be used to treat actinic (solar) keratosis, basal cell carcinomas and Bowen's disease (squamous cell carcinoma in-situ). Actinic keratoses are dry scaly patches of skin that are caused by chronic sun exposure. The patches are considered pre-cancerous and while most do not go on to develop into skin cancer, treatment is generally advised. Basal cell carcinoma and squamous cell carcinoma are two types of skin cancer that also most often develop as a result of long-term UV exposure.
Your PDT appointment – what to expect
The first step is to prepare your skin. Your skin will be cleansed and any scale or crusts are gently removed. The photosensitising cream is applied to the area of your skin to be treated. A dressing is then placed over the cream, and you will be asked to return to the clinic after several hours. This wait is to allow the inactive photosensitiser to be absorbed into the skin and activated. The area is then cleansed again and exposed to red light for up to 30 minutes. After the treatment has been completed, a dressing will be applied which is to be kept on, usually for two days, to prevent any further exposure to light. Depending on the type of skin lesion being treated, the entire process may be repeated one week later.
Your PDT appointment – aftercare and downtime
It is important to protect the treated area in the days after photodynamic therapy. You will be given detailed instructions on how to care for your skin. Some patients find that the area may weep slightly and form a crust, this is normal. It is possible that the condition may reoccur or some lesions may persist after PDT. Dr. Alexis will discuss having further photodynamic therapy or an alternative treatment if needed.