Photodynamic Theraphy – PDT

What is PDT?

Photodynamic therapy is the use of a photosensitizing (light sensitive) drug in combination with light therapy to destroy cancer cells. It is used for treating cancer cells on the skins surface or just under the skins surface (not melanoma) or in the lining of internal organs and is mainly done as an outpatient procedure. PDT can only be used to treat cancers that can be exposed to light.

In the early stages of cancer, PDT may be used as a curing agent. However, in the advanced stages, it is mainly used to reduce symptoms.

How does PDT work?

A light sensitive drug is either applied to the skin’s surface or injected into the bloodstream depending on the type of cancer being treated. The drug then is absorbed by the cancer cells over a period of time which can vary from a couple hours to a couple of days depending on what drug is used. After the waiting period is over, a light source is applied to the area to be treated. This activates the drug and the drug then kills the cancer cells and/or killing the blood vessels feeding the cancer cells. It also triggers the immune system to attack the cancer.

What are the side effects of PDT?

After treatment, the area that was exposed to the light will be sensitive and may be swollen. Medicine may be prescribed for pain and discomfort. The photosensitizing drug will cause the patient’s skin to be very sensitive to light, therefore caution should be exercised when venturing outside or even going into a bright room. It is recommended to keep the skin’s surface covered for a few days or even a week or two after the procedure. Even sunscreen will not protect the skin. Your doctor will inform you of any precautions you should take. Other temporary side effects include constipation and nausea.

For side effects from specific treatment of different, visit this website:

The future of PDT

Researches have an optimistic view for the future of PDT. Newer photosensitizing drugs are now being developed that may be able to treat in a more efficient manner. The American Cancer Society’s website listed the following advancements in these drugs:

-They will be able to treat tumors that are deeper under the skin or in body tissues.

-They may be more selective for cancer cells rather than normal cells.

-They may collect in cancer cells more quickly reducing the time needed between getting the drug and receiving the light therapy.

-They may be removed from the body more quickly, reducing the time people need to worry about photosensitivity reactions.

-They may start to respond to small doses of radiation as well as light allowing doctors to use smaller amounts of radiation leading to fewer side effects.

Another advancement is the possibility of using PDT during surgery to help prevent the recurrence of cancer on large surface areas.

PDT in combination with the drug aminolerulinic acid (ALA) is being studied for the treatment of basal and squamous cell carcinomas. Researchers are excited with results showing tumors healing in one or two sessions. It is even possible that PDT-ALA may even prevent the development of sqaumous cell carcinomas. Along with treating cancer, PDT-ALA has been used for cosmetic procedures to rejuvenate sun-damaged or aging skin.

Information gathered from the following sources:

American Cancer Society-

Cancer Back Up-