Photodynamic therapy is a treatment for non melanoma skin cancer and an experimental treatment for some other types of cancer.
What it is
Photodynamic therapy (PDT) is also called:
- photoradiation 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. 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 might have the chemical as a tablet or injection.
After the drug has been absorbed, your doctor shines a strong light on to the treated area for up to 45 minutes. The light kills any cell that has absorbed the drug.
PDT for cancers inside the body
Researchers are looking at PDT to treat 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)
- wind pipe (bronchus)
PDT is mainly used to shrink larger cancers that are blocking the airway or food pipe. It 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.
Having PDT for internal cancers
Your 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, your 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).
You might have a thin tube put up your nose or into your throat to give the treatment if the cancer is in the head area.
You might have a tube put into the foodpipe (endoscopy) if the cancer is in your foodpipe or stomach. The tube goes into your main airway (bronchoscopy) if the cancer is in the airways.
When the tip of the tube is close to the cancer the doctor switches on the laser light. You might have this under local or general anaesthetic.
Where you have PDT
You usually have PDT in the outpatient department. You might have it in combination with other treatments such as:
- biological therapy
Side effects of PDT
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:
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.