Photodynamic therapy (PDT) at Guildford Hospital

What is photodynamic therapy?

Photodynamic therapy (PDT) involves the use of light, oxygen and photosensitising agents (which by itself is harmless) to treat certain pre-cancerous and non-melanoma skin cancers.

This interaction causes the damaged skin cells to die and new normal cells can grow.

What can photodynamic therapy be used to treat?

Topical PDT is used to treat:

• Actinic keratosis - early sun-damaged, pre-cancer
• Bowen’s Disease - a pre-cancer to squamous cell carcinoma
• Superficial and nodular Basal Cell Carcinomas.

A biopsy will be conducted to indicate which condition who have before being treated with photodynamic therapy.

What happens during photodynamic therapy?

There are two ways of delivering topical PDT:

• Red light activated PDT
• Daylight activated PDT

Red light activated PDT

This involves the application of a photosensitising gel and illumination under a red light. The gel helps stimulate a process which helps destroy the damaged cells and leaves the healthy ones intact when the light is applied.

The doctor may ask you to apply a moisturiser the week before your appointment to the affected area to soften any crusts or scales on your skin.

On the treatment day the area to be treated will be cleaned and any crusts or scales gently removed. The gel will be applied to the area followed by a dressing. The gel is left to incubate for approximately 3 hours - you will be advised on the return time. After 3 hours the dressings are removed and excess gel wiped off. You will be asked to sit or lie in a comfortable position and the treatment area will then be illuminated for approximately 8-10 minutes. You will be given special goggles to protect your eyes from the light.

You may feel some tingling and discomfort this is perfectly normal and is the gel reacting to destroy the damaged cells. After treatment, a dressing is usually applied for 24-48 hours.

What happens next?

Some lesions such as Bowen’s disease and Basal Cell Carcinomas, need to be treated twice, 7 days apart and you will be told if this is necessary for you. You can expect the area to be inflamed and crust for up to 7-14 days while the damaged cells are shed and replaced with new healthy ones. Your Dermatologist will advise as to your follow-up appointment.

Daylight activated PDT

This is a treatment for either individual Actinic keratosis lesions or field areas of sun-damaged skin. It involves the application of a photosensitizing gel and the use of daylight to activate the gel. The gel starts a process in the damaged cells which helps destroy them while leaving the healthy skin intact.

Your dermatologist may ask you to apply a moisturiser the week before your appointment to the affected area to soften any crusts or scales on your skin.

The first step in treatment will be to apply sunscreen to the area to be treated as well as other exposed areas. It's important to avoid any further sun damage, but the sunscreen must not contain any physical sunblocks or filters, for example, titanium dioxide, which would interfere with the effectiveness of the treatment. The area to be treated is then cleaned with an alcohol wipe and any crust or scales will be gently removed. The gel is applied in a thin layer and within the next 30 minutes you will be asked to go outside and stay in full daylight for 2 hours. Many clinics have a garden area to sit in outside or you may prefer to continue the treatment at home if you live nearby. You don’t need full sun, just daylight, so take some shelter if it’s too hot and sunny.

During the treatment you may experience some tingling in the sun-damaged areas this is a normal part of the process. After 2 hours any excess gel should be removed and the treated are protected with a hat/clothing or sunscreen.

What happens next?

You can expect the area to be inflamed and crust for up to 7-14 days while the damaged cells are shed and replaced with new healthy ones. Your dermatologist will advise as to your follow-up appointment.

Post-treatment and aftercare

Your treatment radiographer will explain how you should care for the treated areas. It is usually suggested that the dressing should be kept in place for 48hrs and once removed you can wash, bathe, or shower as usual. Do not rub the treated area, but gently pat it dry.

Within a few days, a scab will form, and healing will take several weeks (depending on which part of the body has been treated). Care must be taken not to scratch the area or accidentally dislodge the scab during the healing process. The use of a suitable sunscreen (SPF 30) following the procedure, especially during outdoor activities, is important.

What are the side effects of photodynamic therapy?

• Pain - When the red light is shone onto the skin, the treated area may tingle and burn. If it is too uncomfortable, the radiographer may suggest pausing treatment for a while, or a cool water spray and fan may be used. After completion of treatment, inflammation and itching may last for a few days, and may require painkillers.
• Inflammation - The treated area may initially become pink and puffy, and may ooze a little: this is a normal reaction. It settles within a few days.
• Blistering and ulceration - The treated area may occasionally blister or ulcerate. This is very rare.
• Infection - If the treated area becomes red, swollen and painful, an infection may have developed, and you should contact your doctor.
• Colour change - The skin may be left darker or paler after PDT.
• Treatment may not always be effective, or the condition may re-occur. If this happens, you may be offered further PDT, or an alternative type of treatment may be recommended.