Photodynamic therapy (PDT)

Photodynamic therapy is used to treat some cancers and precancerous conditions such as skin (but not melanoma), head and neck, mouth, lung and gullet cancers.

PDT involves two steps.

First, a light-sensitive drug is given. For skin cancers, it may be a cream. For internal cancers, it may be an injection into a vein, or rarely a drink. You then wait a few hours to a few days before the next step. This allows time for the drug to concentrate in the cancer cells.

Next, a special light (usually a laser) is shone onto the cancer. The light activates the drug to treat the tumour. If the cancer is internal, an ultrasound or scan may be used to guide the light source to the tumour.

The side effects can vary depending on where treatment is given, what drugs are used, and how you react. You may become sensitive to light for a time, and will need to take care in the sun, or other bright lights.

How PDT works

Photodynamic therapy (PDT) is a treatment that uses a light-sensitive drug and a laser or light source to destroy cancer cells.

The light-sensitive drug is sometimes called the photosensitising agent. It is a drug that makes cells more sensitive to light. This is called photosensitivity.

The drug is attracted to the cancer cells. It does not become active until it is exposed to a particular type of light. When the light is directed at the area of the cancer, the drug is activated and the cancer cells are destroyed. Some healthy, normal cells in the body will also be affected by PDT, but these cells will usually heal after the treatment.

When PDT is used

PDT is used to treat some cancers and conditions that may develop into a cancer if not treated (pre-cancerous conditions). The cancers or areas most usually treated are:

  • skin (but not melanoma)
  • head and neck
  • mouth
  • lung
  • gullet (oesophagus).

PDT is used when the cancer or affected area is on or near the lining of internal organs.

Pre-cancerous conditions

PDT is used to treat pre-cancerous conditions such as Barrett's oesophagus and Bowen's disease of the skin.

Some research studies have used PDT to treat pre-cancerous changes in the cells of the vulva (vulval intraepithelial neoplasia), the vagina and the anus.


When PDT is used to treat early-stage cancers, the aim of the PDT is to try to cure the cancer. When PDT is used for more advanced cancers, the aim is to shrink the cancer and reduce symptoms.

Researchers are trying to find out which types of cancer PDT is most effective for. Clinical trials are looking at new photosensitising agents, new laser and non-laser light treatments, and ways of reducing the side effects. You may be offered PDT as part of a trial.

Your hospital doctor can tell you whether PDT is an appropriate treatment in your situation.

How PDT is given

The treatment is normally given in two stages.

Stage 1

The first stage of treatment is when you are given the photosensitising agent. For skin cancers, the drug is usually applied to your skin as a cream. For cancers that are inside the body, the drug may be given as a drink or more usually as an injection into a vein (intravenously).

There is a delay between the drug being given, or the cream being applied, and the second stage of treatment. This allows time for the drug to concentrate in the cancer cells. The length of time you need to wait for the second stage of treatment after having the drug can vary from hours to days.

There are several drugs that can be used as the photosensitising agent. The most common are 5-aminolevulinic acid (ALA), temoporfin (Foscan®) and porfimer sodium (Photofrin®). The drug used will depend on the type of cancer you have and which is best for your situation. Your doctor or nurse will explain which drug will be used and how it will be given.

Stage 2

The second stage of treatment involves shining a laser or sometimes a non-laser light directly on to the cancer or the affected area.

For skin cancers, the light is shone directly on to the skin. For internal cancers, a flexible tube (endoscope) may need to be passed into your body to deliver the light to the tumour. Depending on where the cancer is in the body, a scan or ultrasound may be used to help direct the light to the tumour.

Possible side effects of PDT

As with all kinds of treatment, the experience of PDT can vary from person to person. How the treatment is given and the side effects it may cause vary depending on:

  • the area of the body being treated
  • the type of photosensitising drug
  • the amount of time between giving the drug and applying the light
  • how sensitive your skin is to light after the treatment.

The possible side effects of PDT for different cancers or areas of the body are explained below.

Skin cancer and Bowen's disease

PDT can be used instead of surgery to treat basal cell skin cancers and Bowen's disease (a pre-cancerous skin condition). It's also used to treat areas of raised, rough skin that are sensitive to the sun (known as actinic keratoses), which have a small risk of developing into skin cancer.

Before your treatment, your nurse or doctor will remove any crusting from the affected area of skin. This makes it easier for the photosensitising cream to reach the affected cells. They will then apply the cream to the affected area and cover it with a dressing to protect it.

You'll have to wait about 3–6 hours to allow time for the cream to work before you have the second stage of your treatment. The length of time you wait varies, depending on the skin condition being treated.

In the second stage of treatment, you'll be asked to sit or lie down in a comfortable position. A strong light is shone directly on to the affected skin. This can take 8–45 minutes, depending on the procedure you're having. The treatment is often repeated a week later.

Possible side effects

Sensitivity to light

The treated area of skin will be sensitive to daylight and bright, indoor lighting. This effect will probably last for 24-36 hours. You will need to keep the treated area of skin covered during this time. After that you can wash and have a bath or shower as usual, but you will need to treat your skin gently and avoid rubbing the area until it has healed.


When you’re having the treatment, you may feel a bit of discomfort, like a burning sensation. A cooling fan and/or a water spray can sometimes be used to relieve this. Some hospitals use a special machine that delivers cool air to the treated area. Taking painkillers before the treatment may also help. You may have a local anaesthetic to numb the area before the treatment. You may be given some steroid cream to apply at home if your skin is still sore.


A scab will form on the treated area. This usually falls off after about three weeks. The area usually heals quickly without scarring.

Head and neck cancers

PDT may be used for early-stage cancers of the head and neck to try to cure the cancer. It is usually given as part of a clinical trial. PDT can also be used in advanced cancer to shrink the tumour and reduce symptoms.

First, you have the photosensitising drug as an injection through a small tube (cannula) inserted into a vein. This takes a few minutes and then the tube is removed.

You will have to wait up to four days before having the second stage of your treatment (when the light is directed at the cancer cells). Your doctor will tell you when you need to come back to the hospital this.

Generally, only one treatment is given, although some people need a second treatment a few weeks later.

Possible side effects

Sensitivity to light

Although the photosensitising drugs are mostly taken up by the cancer cells and are concentrated there, they can also make your ordinary skin cells or your eyes highly sensitive to light. This is known as photosensitivity. How long this lasts will vary, depending on which drug is used.

The drug temoporfin (Foscan®) is commonly used to treat head and neck cancers. It can make you sensitive to direct sunlight for up to a month. During this period, you’ll be given specific instructions from your hospital team about protecting yourself from sunlight and bright indoor lighting. You will need to follow these instructions carefully to avoid burning your skin.

Your hospital team will give you advice on using lights inside your home, as well as other ways to avoid or reduce your exposure to strong light sources. Strong light sources include spotlights, fire, TV or even sunlight shining through a window. You will also be told when you are able to go outside and what clothing you should wear to protect your skin from sunlight.

You may be given a device called a portable light meter. You can use this to help measure the levels of light. If you are given a light meter, the staff who are treating you will explain how to use it.

When enough time has passed after your treatment, your doctor may ask you to check the photosensitivity of your skin. This usually involves exposing a small area of your skin to bright light for five minutes and assessing the reaction 24 hours later. Your doctor or nurse will explain this in more detail. As your skin becomes less sensitive to light, you will be given advice about gradually increasing the amount of light you're exposed to. You will also be given advice about any skin protection you need to continue with.

Eye checks

You should avoid having your eyes checked and light shone into your eyes while you're sensitive to light. This is because the area at the back of your eye (retina) will be more sensitive to light than usual.


PDT can cause pain in the tumour area. Your specialist nurse will explain how this may affect you and make sure that you have the right kind of painkillers. The amount of pain can vary, depending on where your tumour is and which photosensitising drug has been used.

Some people may only need simple painkillers such as aspirin or paracetamol. Others may need a stronger drug such as morphine. Let your doctor know if you have any pain.


Some photosensitising drugs can cause swelling in the treated area. This varies from one person to another. If you've had treatment in your mouth or throat, the swelling may make it difficult for you to swallow. The swelling is temporary but can be treated with steroid injections or drugs that help reduce inflammation. It's important to let your nurse or doctor know if swallowing becomes difficult.

Feeling sick (nausea)

Some people may feel sick, but this can be controlled with anti-sickness (anti-emetic) tablets.


PDT causes much less scarring than surgery. However, the amount of time it takes for areas treated withn for PDT-treated areas to heal can vary. It may be several weeks, depending on the area treated and how deeply the light has penetrated into the body’s tissues.

Other instances when PDT is used

Cancers in other parts of the body

PDT is often given as part of a research trial when it is used to treat cancers in other parts of the body.

Early cancers

PDT can sometimes be used to treat some small, early lung cancers in people who can't have surgery. It may also be given alongside surgery as part of a clinical trial to treat glioblastoma multiforme brain tumours.

Advanced cancers

PDT may be used to relieve the symptoms of some advanced cancers.

Very occasionally, it can be used to relieve breathlessness and swallowing difficulties in people with advanced cancer of the lung or gullet (oesophagus).

Possible side effects

Many of the side effects of PDT for these cancers will be similar to those described in the section on PDT for head and neck cancers.

The amount of time you’ll be sensitive to light will vary from one or two days to several months. This depends on which photosensitising drug is used. During the period, you will need to protect your skin from very bright light. Your doctor or nurse will give you information about this.

Some people may have pain or discomfort, or feel sick. These side effects can be controlled with painkillers and anti-sickness drugs.

Cancer and pre-cancer of the gullet (oesophagus)

Swelling and inflammation can occur around the treatment area. This may make you feel sick and cause chest pain. You may find swallowing difficult for a few days.

Cancer of the lung

PDT may cause swelling and inflammation in the lung, which may cause some chest pain, a cough and breathlessness.

You may produce more sputum (mucus), and rarely it may be bloodstained. Occasionally, there may be a build-up of fluid in the lining of the lung. This is known as a pleural effusion and it can be drained if necessary.

Brain tumours

Possible side effects of PDT for brain tumours may include swelling and increased pressure in the brain.

Let your doctor or nurse know about any side effects you have.

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