Photodynamic therapy (PDT)
Photodynamic therapy (PDT) is a treatment for some cancers and conditions that may develop into a cancer.
We hope this information answers your questions. If you have any further questions, you can ask your doctor or nurse at the hospital where you are having your treatment.
PDT uses laser, or other light sources, combined with a light-sensitive drug (sometimes called a photosensitising agent) to destroy cancer cells.
A photosensitising agent is a drug that makes cells more sensitive to light. 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.
PDT can be used to treat some cancers or conditions that may develop into a cancer if not treated (pre-cancerous conditions). It’s used when the affected area, or the cancer, is on or near the lining of internal organs. This is usually with cancers or conditions that affect the:
Researchers are trying to identify the types of cancer PDT is most effective for. Trials are also 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.
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 affecting the vulva (vulval intraepithelial neoplasia, or VIN), the vagina and the anus.
In cancers that are being treated at an early stage, the aim of PDT treatment is to try to cure the cancer. With more advanced cancers, the aim of PDT is to shrink the cancer and reduce symptoms.
Your hospital doctor can advise you whether PDT is an appropriate treatment in your situation.
The treatment is normally given in two stages.
The first stage of treatment involves giving the photosensitising agent. For skin cancers, the drug is usually applied to the 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 next stage of treatment. This allows time for the drug to concentrate in the cancer cells. The length of time you need to wait for 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.
The second stage of treatment involves shining a laser or sometimes a non-laser light directly on to the cancer.
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 laser light to the tumour.
Possible side effects of PDT
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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 according to:
the area of the body being treated
the type of photosensitising drug
the amount of time between giving the drug and applying the light
the amount of skin sensitivity to light following treatment.
The paragraphs below explain how PDT is used for skin cancer and Bowen’s disease, head and neck cancers, cancer and pre-cancer of the gullet, lung cancer and brain tumours.
Skin cancer and Bowen's disease
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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 you have your treatment, your nurse or doctor will first remove any crusting from the affected area of skin. This makes it easier for the photosensitising cream to reach the affected cells.
The first stage of your treatment will then involve your doctor or nurse applying a photosensitising cream to the affected area of your skin. This will be covered with a dressing to protect it.
You'll have to wait for 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. When you come back for the second stage of your treatment you'll be asked to sit or lie down in a comfortable position. A strong light is then shone directly on to the affected skin. This can take 8-45 minutes depending on the particular procedure you're having. The treatment is then 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, bath or shower as usual, but you will still need to treat your skin gently and avoid rubbing the area until it has healed.
You may feel a bit of discomfort, like a burning sensation, when you're having the treatment. 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 some painkillers before the treatment also helps. Occasionally, some people 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 treated with PDT usually heals quickly without scarring.
Cancers in the head and neck
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PDT may be used in 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.
With head and neck cancers, the first stage of treatment involves giving 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 about 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 for this stage of your treatment.
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. The duration of sensitivity to light (photosensitivity) varies depending on which drug is used.
The drug temoporfin (Foscan®) is commonly used to treat head and neck cancers and will make you sensitive to direct sunlight for at least a month.
During this period of skin sensitivity, you’ll be given specific instructions from your hospital team about protecting yourself from exposure to sunlight and bright indoor lighting. You will need to follow these instructions carefully to avoid burns to the skin.
The instructions your hospital team give you will include advice on using lights inside your home, as well as other measures to avoid 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 photosensitive, you will be given advice about gradually increasing the amount of light you're exposed to and any skin protection you need to continue with.
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 vulnerable to light than usual.
Treatment with PDT can cause pain in the tumour area. Your specialist nurse can explain how this may affect you and make sure that you have the right kind of painkillers to take. 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 to 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 time taken 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.
Cancers in other parts of the body
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PDT is often given as part of a research trial when it is used to treat cancers in other parts of the body.
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 some types of brain tumours.
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 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, ranging from one or two days to several months. This depends on which photosensitising drug is used. During the period of photosensitivity you will need to protect your skin from 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. Other side effects will depend on the part of the body that is treated. Let your doctor or nurse know about any side effects you have.
Cancer and pre-cancer of the gullet (oesophagus)
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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.
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.
Possible side effects of PDT for brain tumours may include swelling and increased pressure in the brain.
This section has been compiled using information from a number of reliable sources, including:
British Medical Association and Royal Pharmaceutical Society of Great Britain. British National Formulary. 64th edition. 2012.
National Institute for Health and Clinical Excellence (NICE). Photodynamic therapy for brain tumours. 2009.
National Institute for Health and Clinical Excellence (NICE). Barrett's Oesophagus: ablative therapy for the treatment of Barrett's oesophagus. 2010.
National Institute for Health and Clinical Excellence (NICE). Photodynamic therapy for early oesophageal cancer. 2006.
National Institute for Health and Clinical Excellence (NICE). Palliative photodynamic therapy for advanced oesophageal cancer. 2007.
Tobias, Hochauser. Cancer and its management. 6th edition. Blackwell Scientific Publications. 2010.
With thanks to: Carol Goodman, Clinical Nurse Specialist, Scottish Photodynamic Therapy; and the people affected by cancer who reviewed this edition.
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