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This information is about photodynamic therapy (PDT). PDT is a treatment for some types of cancer. It may also be used to treat some non-cancerous conditions of the skin or eye.
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. Once in the body, the drug is attracted to cancer cells. It does not do anything 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, although 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 (precancerous). It is 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:
Doctors are working to identify the types of cancer for which PDT is most effective. Research trials are taking place to look at new photosensitising agents, new laser and non-laser light treatments and ways of reducing the side effects.
Precancerous conditions PDT is used to treat precancerous conditions, such as Barrett's oesophagus and Bowen's disease of the skin.
Some research studies have used PDT to treat precancerous changes in the cells affecting the vulva (vulval intraepithelial neoplasia or VIN), the vagina and the anus.
Cancer In cancers that are being treated at an early stage, the aim of treatment may be to try to cure the cancer.
The aim of PDT for advanced cancer is usually to reduce symptoms by shrinking the tumour. In this situation PDT cannot cure a cancer.
PDT treatments for some cancers, such as prostate and pancreas, are still being researched.
Your doctor can advise you about whether PDT is an appropriate treatment in your situation, and whether you may be able to take part in any research trials.
PDT can safely be given to patients who have had other cancer treatments such as surgery, radiotherapy and chemotherapy.
The treatment is normally in two stages.
Stage 1 A light-sensitive drug is given. For cancers of the skin, the drug is usually applied to the skin as a cream.
For cancers that are inside the body, the drug is usually given by injection into a vein (intravenously). There are some drugs that can be given by mouth.
There is a delay between the cream being applied, or the drug being given, and the next stage of treatment. This allows time for the drug to concentrate in the cancer cells.
Stage 2 The second stage of treatment involves shining light directly on to the cancer. A laser delivers energy in the form of light in a very precise way. Special non-laser lamps may also be used in some situations. For skin cancers, the light is shone directly onto the skin. For internal cancers, a flexible tube (an endoscope) may need to be passed into your body to deliver the light to the tumour.
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 that it may cause vary, according to:
When PDT is used to treat skin cancer, the side effects are different to when PDT is used for a cancer elsewhere in the body.
A photosensitising cream will be applied to the affected area of skin. You will then need to wait for approximately 4–6 hours before being treated. Treatment with the PDT light will last 20–45 minutes, after which a dressing will be put on to cover the area and protect it from light. Usually only one treatment is needed, but occasionally two or three further treatments may be given.
The photosensitising drug is given 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 then have to wait up to about four days before the light treatment is given. The length of time varies depending upon the particular photosensitising drug you've been given. Generally, only one treatment is given, although it is possible to have a second treatment a few weeks after the first.
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. People who have had PDT are advised to protect themselves from exposure to sunlight and bright indoor lighting. The duration of sensitivity to light (photosensitivity) varies depending upon 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 up to a month.
While your skin is photosensitive, it is advisable to avoid going outside during the day. However, you do not need to stay in total darkness during this time. To start with you will need to stay in a darkened room, but you can gradually build-up the amount of light over two weeks. If you need to go out, use clothing to cover your skin: for example, wear a brimmed hat, scarf, long-sleeved shirt or blouse and trousers, gloves and dark glasses. Using sunscreens will not give you any additional protection.
You can go out uncovered very early in the morning or after sunset, and you can use low-level artificial light indoors (maximum 60W bulb). In the first few days it is possible to get ‘sunburn’ even on a dull winter day. You will not notice that you are getting burnt while you are out in the sun. As with sunburn, the damage to your skin can take a few hours to show up.
You can even get burnt through glass if the light is strong. Remember to draw curtains during the day if the sun is bright. Bright artificial lights can also cause a skin reaction, so spot lamps are best avoided. It is important to be aware of unexpected sources of light – for instance, warming your hands over a fire could result in being burnt. It is also a good idea not to use a computer during this time and not to watch the television from less than about 2 metres (6 feet) away. You may be given a light meter to use at home, to check that the light intensity is at a safe level.
It is advisable to avoid opticians’ appointments around the time of your treatment, as the retinas inside your eyes will be more vulnerable to light than usual, and you should not have light shone into your eyes.
Towards the end of the time of photosensitivity, a small area of skin can be exposed to brighter light for five minutes and the reaction assessed 24 hours later. Your doctors will advise you on how to do this. After this time, you will be able to gradually increase the amount of light you are exposed to and most people are able to go outside as usual after approximately three weeks. Your doctor or specialist nurse can let you know for exactly how long you will need to protect your skin.
Pain Treatment with PDT can cause pain in the tumour area. Your specialist nurse should be able to tell you how much pain you might expect and see that you are given appropriate painkillers. The amount of pain will vary according to where your tumour is and which light-sensitising drug has been used. Pain can range from mild to severe. For some treatments aspirin or paracetamol may be enough, however for others a morphine-type drug may be necessary. If you have pain, it is important to let your doctor know, so that you can be given effective and appropriate painkillers.
Swelling Some photosensitising drugs can cause swelling in the treated area. This varies from one person to another. If you have had treatment in your mouth or throat, the swelling may make it difficult to swallow. It is important to let your nurse or doctor know if swallowing becomes very difficult. The swelling is only temporary but can be treated with steroid injections or drugs that help to reduce inflammation.
Constipation This is a fairly common side effect of PDT and you may need to ask your doctor for medication.
Feeling sick (nausea) Some people may feel sick, which can be controlled with mild anti-sickness tablets if necessary.
Healing PDT causes much less scarring than surgery. However, the time taken for PDT-treated areas to heal can vary a lot. It may be several weeks, depending on the area treated and how deeply the light has penetrated into the body tissues.
Other than skin cancer, and cancers of the head and neck, PDT is most commonly used to treat precancerous changes and early cancers, found in the inner lining of the digestive system and the lungs.
However, as PDT is a new treatment, it may start to be used for other cancers. If the cancer is on the lining of an internal organ such as the gullet (oesophagus), stomach or lungs, it may be necessary for a thin, flexible tube to be passed into the windpipe or gullet to bring the laser light as close to the cancer as possible.
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 that you have and which is best for your situation. These drugs may be given as a drink or tablets or as an injection. The way that the drug is given will depend on which one is best for your treatment.
The length of time you need to wait for treatment after having the drug can vary from 90 minutes to four days. You will be told which drug will be used and how it will be given. You will also be told whether treatment as an outpatient or if you will need to stay in hospital.
PDT drugs for cancers in other parts of the body are usually given by injection into a vein. Many of the side effects will be similar to those experienced by people who have had PDT for head and neck cancers. The time of sensitivity to light (photosensitivity) varies, ranging from one or two days to several months. This depends on which photosensitising drug is used. Your doctor or specialist nurse can let you know the length of time you will need to protect your skin.
You may also have some pain, feelings of sickness and constipation. Other side effects will depend upon the part of the body that is treated.
Cancer and pre-cancer of the gullet (oesophagus) Swelling and inflammation can occur around the treatment area and may make you feel sick and cause chest pain. This may make swallowing difficult for a few days.
Cancer of the stomach The lining of the stomach may become inflamed and swollen, causing abdominal discomfort and feel sick.
Cancer of the lung The PDT may cause swelling and inflammation in the lung which may cause some chest pain, a cough and breathlessness. You may notice that you are producing more sputum and rarely you may cough up blood-stained sputum. Occasionally there may be a build-up of fluid in the lining of the lung (a pleural effusion), which can be drained if necessary.
Cancer of the prostate PDT as a treatment for prostate cancer is still at an experimental stage. Possible side effects include mild incontinence of urine and difficulty passing urine.
Cancer of the pancreas PDT as a treatment for pancreatic cancer is still at the experimental stage. Possible side effects include abdominal pain and diarrhoea.
This section has been compiled using information from a number of reliable sources including:
For further references, please see the general bibliography.
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