Photodynamic therapy is a treatment for non melanoma skin cancer and an experimental treatment for some other types of cancer.
What is photodynamic therapy (PDT)?
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. The type of photosensitiser and light wavelength you have depends on where the cancer is in your 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 a treatment for some non melanoma skin cancers.
You have a cream that contains the light sensitising chemical put on 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 treatment 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)
You might have PDT 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 is also sometimes a treatment for very early stage cancers in the lung or food pipe when people are not well enough to have other treatments.
How you have PDT
You have a small tube (cannula) put into a vein in your arm or hand. Your doctor injects the light sensitising drug into your bloodstream. 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 on the area to activate the drug.
To shine the light at a cancer inside the body your doctor uses a flexible tube with a light at one end and an eye piece at the other end, such as an endoscope or bronchoscope. 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.
Using an endoscope
Your doctor might use an endoscope for stomach or food pipe (oesophageal) cancer.
Using a bronchoscope
A bronchoscope might be used for cancer in the airways.
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.
Where you have PDT
You usually have PDT in the outpatient department. You might have it in combination with other treatments such as:
- targeted cancer drugs
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 area where you have had treatment. They can include coughing, trouble swallowing, stomach pains, painful breathing, or breathlessness.
The side effects are usually temporary.