Photodynamic Therapy
(PDT or Blue Light Therapy)

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Medical Author: Nili N. Alai, MD, FAAD
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

• What is photodynamic therapy (PDT)?
• What photosensitizer drugs are available?
• What light sources are available, and how are they applied?
• How does PDT work?
• Does PDT make me permanently more sensitive to light?
• How is PDT used to treat the skin?
• What is a typical skin PDT session like?
• How much improvement can I expect?
• Where can I have photodynamic therapy, and who performs the procedure?
• What are the advantages with photodynamic therapy for treating skin precancers?
• Am I a good candidate for photodynamic therapy?
• What growths is PDT not good for?
• What are possible complications of photodynamic therapy?
• Is there scarring from photodynamic therapy?
• What are alternatives for photodynamic therapy?
• What about insurance coverage and costs?
• What about other treatments options?
• How do I prepare for my procedure?
• How is recovery?
• Is there pain after PDT?
• How do I take care of my treatment area after photodynamic therapy?
• What is the chance that my precancers will recur?
• Find a local Dermatologist in your town

What is photodynamic therapy?

Photodynamic therapy (PDT) is a medical treatment that uses a photosensitizing drug (a drug that becomes activated by light exposure) and a light source to activate the applied drug. The result is an activated oxygen molecule that can destroy nearby cells. Precancerous cells and certain types of cancer cells can be treated this way. The procedure is easily performed in a physician's office or outpatient setting.

PDT essentially has three steps. First, a light-sensitizing liquid, cream, or intravenous drug (photosensitizer) is applied or administered. Second, there is an incubation period of minutes to days. Finally, the target tissue is then exposed to a specific wavelength of light that then activates the photosensitizing medication.

Steps:

1. application of photosensitizer drug
2. incubation period
3. light activation

Although first used in the early 1900s, PDT in the modern sense is a fairly new, evolving science. Current PDT involves a variety of incubation times for the light-sensitizing drug and a variety of light sources depending on the target tissue. The basic premise of PDT is selective tissue destruction. Although the photosensitizer may be absorbed all over by many cells, atypical or cancerous cells take up more of the drug and retain the drug for a longer duration than normal tissues.

At present, the primary limitation of available PDT techniques is the depth of penetration of the light and ability to target cells within at most 1/3 of an inch (approximately 1 cm) of the light source. Therefore, tumors or atypical growths must be close to the surface of the skin or treatment surface for PDT to work.

PDT is currently used in a number of medical fields including oncology (cancer), dermatology (skin), and cosmetic surgery.

In oncology, it is FDA approved for non-small cell lung cancer, esophageal cancer, and precancerous changes of Barrett's esophagus. Its use is also being further investigated through clinical trials in general oncology for conditions including cancers of the cervix (mouth of uterus), prostate gland, brain, and peritoneal cavity (the abdominal space that contains the stomach, liver, and internal organs).

Levulan stick (photosensitizer medication)

In dermatology, PDT with the photosensitizer Levulan Kerastick® (20% delta-aminolevulinic acid HCl) is used for the treatment of pre-skin cancers called actinic keratosis (AK). The initial approval was specifically for normal (non-hyperkeratotic) actinic keratosis of the face and scalp with a specified 14- to 18-hour drug incubation time, and 1,000 seconds (16 minutes and 40 seconds) of activation by a blue light source. PDT is also used for acne, rosacea, skin cancer, sun damage, cosmetic skin improvement, oily skin, enlarged sebaceous glands, wrinkles, rejuvenation (anti-aging), warts, hidradenitis suppurativa, psoriasis, and many other skin conditions. It is not used to remove moles or birthmarks.

Application of Levulan to the face