What is photodynamic therapy (PDT)?

PDT is a modern, highly effective treatment for certain types of precancerous lesions affecting the skin, including actinic keratoses (AKs) and Bowen’s disease, as well as superficial basal cell carcinomas (BCCs), one of the so-called, non-melanoma skin cancers (NMSCs).

PDT is a very different approach to the treatment of these lesions compared to the conventional therapies on offer, such as liquid nitrogen (cryotherapy), scraping (curettage and cautery), topical chemotherapy (5- Fluorouracil), other forms of surgery and radiotherapy.

The technique takes advantage of the chemical interaction between light and light-activated drug, leading to a series of chemical reactions resulting in damage and death to diseased cells.

In this way, the surrounding healthy cells are not targeted therefore limiting the tissue destruction to the diseased bit of skin only. This, in turn, reduces the potential for scar formation, resulting in favourable cosmetic outcomes.

What is an actinic keratosis (AK)?

An AK is the term used for a precancerous lesion of the skin arising as a consequence of overexposure to sunlight, resulting in the skin cells growing at an abnormally fast rate. AKs are usually found on the face, tips of ears, backs of hands, forearms and lower legs, and are reddish-brown in colour with a rough rather warty surface.

What is Bowen’s disease?

Bowen’s disease is the term used for a slightly more advanced actinic keratosis, where the abnormal skin cells occupy the full thickness of the outer layers of the skin. They can look similar to AKs, perhaps being slightly thicker and more warty, and more commonly found on the lower legs. Single or multiple lesions can be found.

The patches tend to grow very slowly, and rarely transform into a true skin cancer called a squamous cell carcinoma (SCC).

What is a basal cell carcinoma (BCC)?

BCCs (also known as rodent ulcers) are a type of skin cancer, that either takes the form of a single bump or a series of small bumps. Multiple lesions are sometimes found in the same patient. This type of skin cancer rarely spreads to other parts of the body, however, early treatment is recommended because, if ignored, the tumour can enlarge and become locally invasive.

How is PDT carried out?

Firstly, before the cream is applied, the doctor or nurse will gently remove any crusts and debris. Secondly, the special ALA cream (Metvix) is applied to the area to be treated and covered with a dressing, which should not be disturbed for 3 hours. After 3 hours the cream is carefully removed, the area washed, and a special lamp is brought into position, before being switched on to illuminate the lesion for about 10 to 15 minutes. A cooling fan makes this part of the treatment quite tolerable, without the need for local anaesthetic in most patients. For AKs and Bowen’s disease a single treatment is needed; BCCs require a second treatment after one week.

What follow up is needed?

For actinic keratoses and Bowen’s disease, you will be seen again 3 to 4 weeks later to check the treatment site, and a further appointment will be arranged for you to see Dr Hudson-Peacock 3 months following treatment. If the first treatment is unsuccessful a second session will be considered. For superficial BCCs, 2 treatments will take place one week apart, before the same follow up arrangements as above apply.


To make an appointment to see our Consultant Dermatologist, call 01227 472288. Or you may like to use our online booking system here.