Photodynamic Light Therapy
Photodynamic therapy (PDT), also called photoradiation therapy, phototherapy, or photochemotherapy, is a two-stage treatment process combining special drugs and light therapy that kills cancerous and precancerous cells. Used to treat localized cancers, this procedure can help candidates live longer and improve the quality of their life.
What is PDT?
Photodynamic light therapy could help you live a longer life with less pain
PDT utilizes drugs called photosensitizing agents, and light sources including lasers, light-emitting diodes (LEDs), and lamps. The kind of light used depends on the type of cancer and where it is located in the body. Light therapy works by triggering the body’s immune response, giving your body another means to help destroy cancerous and precancerous cells.
The drugs are administered first, then activated by light therapy. Photosensitizers are activated by a specific wavelength of light energy, usually from a laser. The photosensitizer is nontoxic until it is activated by light. However, after light activation, the photosensitizer becomes toxic to the targeted tissue.
Depending on the part of the body being treated, the photosensitizing agent is either put into the bloodstream through a vein or put on the skin. Once in the body, the drug absorbs the cancer cells. Finally, once activated by the light, the photosensitizing agents become toxic and kill the cancer cells.
PDT is usually done as an outpatient procedure (meaning you won’t have to stay in the hospital) but is sometimes combined with surgery, chemotherapy or other anti-cancer drugs, or radiation therapy.
What can PDT treat?
If you have cancer that has not spread far from where it started, you may be a candidate for PDT. Types of cancer that can benefit from photodynamic light therapy treatment include, but aren’t limited to, pancreatic cancer, bile duct cancer (cholangiocarcinoma) esophageal cancer, certain skin diseases, including precancerous skin changes (actinic keratosis), and nonmelanoma skin cancer, and lung cancer. In some cases, PDT can help treat some infections like bacterial, fungal, and viral infections.
Several photosensitizing agents are currently approved by the US Food and Drug Administration (FDA) to treat certain cancers or pre-cancers. Here are two of the most widely used:
Porfimer sodium (Photofrin) is a very widely used and studied photosensitizer. It’s activated by red light from a laser. It’s approved by the FDA to treat patients with certain kinds of cancers of the esophagus and lung, and is being studied in other types of cancer.
Aminolevulinic acid (ALA or Levulan) is a drug that’s put right on the skin. It’s used to treat actinic keratosis (AK), a skin condition that can become cancer, and is used only on the face or scalp. A special blue light, rather than laser light, is used to activate this drug.
Benefits of PDT
Studies have shown that PDT can work as well as surgery or radiation therapy in treating certain kinds of cancers and precancers. It has some advantages, such as:
No long-term side effects when used properly.
Less invasive than surgery.
Takes only a short time and is usually an outpatient procedure.
It can be targeted very precisely.
Can be repeated many times at the same site if needed, unlike radiation.
Little or no scarring after the site heals.
Often costs less than other cancer treatments.
Limitations of PDT
PDT does have some limits, including:
Can only treat areas where light can reach, including just under the skin or the lining of organs that can be reached with a light source.
Can’t be used to treat cancers that have spread to many places.
Candidates will be highly sensitive to light for some time after
The drugs used for PDT leave people very sensitive to light for some time
Can’t be used in people who have certain blood diseases.
Side effects to watch out for
Each candidate may experience different side effects following their procedure, so be sure to ask your dermatologist what to expect.
Photosensitivity reactions
This procedure will make you more sensitive to light for a while after. This sensitivity can cause reactions that usually involve redness and a tingling or burning sensation. To help manage this, avoid strong, direct sunlight from the outdoors and reflected light following treatment. Stay indoors when possible and wear protective clothing.
Skin changes
Depending on the type and location of treatment, the treated skin might turn red and may swell for a period of time. With some treatments, blisters may form. This may last hours to days after treatment. The skin may also have a burning sensation or may be itchy or change color after treatment.
Immune system changes
Sometimes PDT treatments can make the immune system work differently, either by stimulating it to work more or making it weaker. In very rare cases, PDT can cause skin cancer at the site where treatment was given. Some researchers believe this happens if the immune system is weakened by PDT.
