Photodynamic therapy (PDT) for skin cancer

Photodynamic therapy (PDT) is a relatively new type of treatment. It uses a drug and a special type of light. The light could be a laser or another type of light. The drug is a chemical that makes the skin cells sensitive to light. This type of drug is called a photosensitising agent. The chemical can be introduced by injecting a drug into the bloodstream or it can be applied to the skin in a cream. The drug is absorbed by the body’s cells and makes them sensitive to light. When the area to be treated is exposed to the light the cancer cells are destroyed. 

In February 2006, the National Institute of Health and Clinical Excellence (NICE) issued guidance on PDT for non melanoma skin cancers. They support its use for several types of skin cancer. NICE said there is not much information on how well PDT works for people with squamous cell skin cancers. They felt there was a high risk of this type of cancer coming back or spreading after PDT and they don't recommend its use. But generally, PDT was as good as surgery at controlling basal cell cancers, actinic keratosis and Bowen's disease and is available on the NHS for these conditions.  

NICE say that PDT is best used in cases where you would need a lot of surgery. So it is best for large skin cancers that are not too deep. It is also helpful where there are several cancers in an area. PDT is not suitable for deeper skin cancers because the light cannot penetrate far enough into the skin. In the trials NICE looked at, the appearance of the treated area after PDT was better than after surgery. 

In 2011, NICE published guidance on a particular type of PDT called Ambulight. Ambulight can give photodynamic therapy in places outside hospitals, for example in patients’ homes. It is thought that it may cause less pain than normal photodynamic therapy. But NICE said that although doctors can choose to use Ambulight PDT there is not much evidence about how well it works.

To have PDT treatment, first you have the crust and scale removed from the skin tumour. Then you have a cream that contains the light sensitising chemical applied to the skin cancer and the surrounding area. After the doctor or nurse has applied the cream the affected area will be covered for 3 to 6 hours. This allows the drug to get into the skin cancer cells. The cream contains a drug called 5-aminolaevulinic acid (ALA). Sometimes, you may have the chemical as an injection. 

The 5-ALA makes the skin very sensitive to light. After it has been absorbed, you have a special type of light focused on to the affected area. The light kills any cell that has absorbed the 5-ALA. You can have more than one skin tumour treated at a time and can have the treatment more than once.

The treatment can be done in an outpatient department. Your doctor or nurse will advise you to keep the treated area covered and dry for 36 hours. After that it is fine to bathe or shower if you treat the area gently. It will scab over and the scab falls off on its own about 3 weeks later. If you have a thick skin lesion, you may need another treatment about 4 weeks later.