Photodynamic therapy (PDT)

Photodynamic therapy (PDT) is a treatment for several different types of cancer. It uses a light sensitising drug and a very bright light to destroy cancer cells. 

You can have PDT in different ways. How you have it depends on where the cancer is in your body.  

What is PDT?

Photodynamic therapy (PDT) is a cancer treatment. You have a drug that makes cells sensitive to light. Then the doctor shines a particular type of light on the treatment area. The drug and light combination destroys the cancer cells.

The drug is called a photosensitiser or photosensitising agent. There are different types of light sensitive drugs and different kinds of lights. The type of drug and light you have depends on where the cancer is in your body.

How does PDT work?

The cancer cells absorb the light sensitive drug. The doctor then applies light to the area where the cancer is. The light causes the drug to react and produce a type of oxygen that kills the nearby cells. 

Doctors think PDT might also work in other ways to shrink or destroy tumours. These include:

• the light sensitive drug damaging blood vessels in the cancer. This stops the cancer from receiving nutrients that it needs
• triggering the immune system to attack the cancer cells

Who can have PDT?

PDT is a treatment for several different types of cancer including:

• non melanoma skin cancer
• lung cancer
• some head and neck cancers

Researchers are also looking at PDT for other types of cancer including prostate cancer.

How do you have PDT?

You can have PDT in different ways. How you have it depends on where the cancer is in your body. There are 2 stages:

The light sensitive drug

First you have the light sensitive drug. How you have the drug depends on your cancer type. You can have it as:

• a cream or gel put directly on the skin cancer. You should not have these if you have an allergy to peanuts or soya
• a liquid that you swallow
• an injection into your blood stream

The light treatment

The doctor or specialist nurse shines a light on to the treatment area. They might shine the light:

• directly to your skin -  to treat skin cancer
• through a flexible tube (an endoscope) - to treat cancers inside your body such as lung cancer

How long you wait between having the drug and the light treatment depends on your cancer type. It might be several hours, or several days.

Your doctor or specialist nurse will talk to you beforehand. They will tell you how you will have treatment and exactly what it involves.

Having PDT for skin cancers

The doctor or nurse first cleans the treatment area. They then gently remove any loose crust or scale. Once prepared they apply a light sensitizing cream or gel. This covers the skin cancer and the surrounding skin.

You have a dressing placed over the cream or gel.

After about 3 to 4 hours the nurse or doctor removes the dressing and the cream or gel. The length of time you have the cream or gel on can vary.

They then shine the light on the treatment area for around 10 to 15 minutes. The amount of time the light is shone depends on the type of light being used. 

They put a dressing over the treatment area. You can go home after the treatment. 

Your healthcare team will let you know how to care for the skin afterwards.

Having PDT for cancers inside your body

Before treatment

First you have the light sensitive medicine. You either have it as a liquid that you drink. Or it is an injection through a small tube (cannula) into a vein in the back of your hand.

Having treatment

About 2 to 3 days later, you go to the endoscopy department at the hospital. 

You might have medicine to make you sleepy (sedation). Or you might have a general anaesthetic which means you are asleep.

For lung cancers, your doctor puts a long flexible tube called a bronchoscope into your airways. The tube has a small camera on the end so they can see the cancer. They position the end of the tube close to the tumour and shine a low power laser light at it.

The type of endoscope you have depends on the area of cancer you need treating with PDT.

After treatment

You stay in the endoscopy department or x-ray department until the sedation or anaesthetic wears off. You can usually go home that evening.

A few days after the treatment your doctor might need to remove the dead cells. They do this using an endoscopy tube.

After having sedation or a general anaesthetic you’ll need someone with you so they can take you home and stay with you overnight. Also for 24 hours after you shouldn’t drive, drink alcohol, operate heavy machinery or sign any legally binding documents.

What are the side effects of PDT?

PDT is a safe procedure but as with any medical procedures, there are possible risks. Your doctor makes sure the benefits of having PDT outweigh any possible risks.

Some light sensitising drugs make the skin and eyes sensitive to light for approximately 6 weeks after treatment. This means you need to avoid direct sunlight and bright indoor light for at least 6 weeks. The skin gets very sensitive and may become very red and sore if it is exposed to light during this time.

PDT can cause some damage to nearby healthy tissue. You might notice:

• burns
• swelling
• pain
• scarring

Other side effects of PDT are related to the area where you have had treatment. They can include coughing, trouble swallowing, stomach pains, painful breathing, or breathlessness.

The side effects are usually temporary.

You can read more about side effects of PDT to different parts of the body. There are links above to information about PDT for skin and lung cancer.