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What photodynamic therapy is

Photodynamic therapy (PDT) combines a drug that makes cells sensitive to light with exposure to a particular type of light. The drug is called a photosensitiser or photosensitising agent.  PDT is also called photoradiation therapy, phototherapy, or photochemotherapy. It is a treatment for non melanoma skin cancer and is an experimental treatment for other types of cancer.

How PDT works

PDT works in several different ways to kill cancer cells. Cancer cells take up the drug that makes them sensitive to light. When the cells are exposed to the particular light, they produce a type of oxygen that kills them. Doctors think PDT may also shrink or destroy tumours in other ways.

How you have PDT

For skin cancers you may either have a cream that contains the drug put onto the cancer or you have a tablet or injection of the drug. Once the cells have absorbed the drug the doctor shines a light on the area, usually for about 45 minutes.

For cancers inside the body you have an injection of the drug into your bloodstream, usually through a small tube put into a vein (cannula).  2 or 3 days after the injection the doctor shines the light on the area where the cancer is. To reach the cancer the doctor uses a tube that they put inside your body. For cancers of the airways you have a bronchoscopy. For cancers of the food pipe or stomach you have an endoscopy. PDT for internal cancers can help to relieve symptoms and help you breathe and swallow more easily.

Side effects of PDT

Side effects include sensitivity to light for approximately 6 weeks after treatment. You need to avoid direct sunlight and bright indoor light during this time or your skin may become very red and sore. PDT may also damage healthy tissue near to the cancer cells causing burns, swelling, pain, and scarring. Other side effects of PDT depend on the part of your body treated and are usually temporary. Your treatment team will discuss the possible side effects with you.

 

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What photodynamic therapy is

Photodynamic therapy (PDT) is a treatment for non melanoma skin cancer and is an experimental treatment for some other types of cancer. It is also called photoradiation therapy, phototherapy, or photochemotherapy. 

PDT combines a drug that makes cells sensitive to light with exposure to a particular type of light. The drug is called a photosensitiser or photosensitising agent. There are different types of sensitising drugs and each is activated by light of a specific wavelength. Different photosensitisers and light wavelengths are used to treat different areas of the body.

 

How PDT works

When the sensitising drugs are exposed to their particular light, they produce a type of oxygen that kills nearby cells. PDT directly kills cancer cells, but doctors think it also acts in other ways to shrink or destroy tumours. The sensitising drug may damage blood vessels in the tumour, and stop it from receiving nutrients that it needs. PDT may also trigger the immune system to attack the cancer cells.

 

PDT to treat skin cancer

PDT is used to treat some non melanoma skin cancers. You have a cream that contains the light sensitising chemical applied to the skin cancer and the surrounding area. Sometimes, you may have the chemical as a tablet or injection. After the drug has been absorbed, you have a strong light shone on to the treated area for up to 45 minutes. The light kills any cell that has absorbed the drug. 

We have detailed information about PDT for skin cancer in the skin cancer treatment section.

 

PDT for cancers inside the body

Some research seems to show that PDT can be helpful for some types of cancer inside the body. But we need more research to find out which cancers it can help with and how best to use it. 

The light used for PDT can only pass through about 1 centimetre (one third of an inch) of tissue. So, doctors usually use PDT to treat cancers on the lining of internal organs or cavities, such as in the head and neck area, the food pipe (oesophagus) or wind pipe (bronchus). 

PDT is mainly used to shrink larger cancers that are blocking the airway or food pipe. The treatment can relieve symptoms and help people to breathe or swallow more easily. It may sometimes be used to treat very early stage cancers in the lung or food pipe when people are not well enough to have other treatments such as surgery, or chemotherapy combined with radiotherapy.

 

Having PDT for internal cancers

First the doctor injects the light sensitising drug into your bloodstream. This is usually through a small tube put into the vein (a cannula). Cells all over the body absorb the drug but it stays in cancer cells longer than in normal cells. Approximately 2 to 3 days after the injection, the doctor shines a light to activate the drug. 

To shine the light at the tumour inside the body the doctor usually needs to put a flexible, light bearing tube inside the body (an endoscope).

If the cancer is in the head area you may have a thin tube put up your nose or into your throat to give the treatment. 

If the cancer is in the foodpipe or stomach you have a tube put into the foodpipe (an endoscopy). 

If the cancer is in the airways, the tube goes into the main airway (bronchoscopy).

When the tip of the tube is close to the cancer the doctor switches on the laser light. You may have this part of the treatment under local or general anaesthetic.

 

Where you have PDT

You usually have PDT in the outpatient department. You may have it in combination with other treatments, such as surgery, radiotherapy, biological therapy or chemotherapy

 

Side effects of photodynamic therapy

Some light sensitising drugs make the skin and eyes sensitive to light for approximately 6 weeks after treatment. So, 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 such as burns, swelling, pain, and scarring. Other side effects of PDT are related to the treated area. They can include coughing, trouble swallowing, stomach pains, painful breathing, or breathlessness. The side effects are usually temporary.

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Updated: 26 September 2013