Photodynamic Therapy (PDT or Blue Light Therapy)

  • Medical Author:
    Gary W. Cole, MD, FAAD

    Dr. Cole is board certified in dermatology. He obtained his BA degree in bacteriology, his MA degree in microbiology, and his MD at the University of California, Los Angeles. He trained in dermatology at the University of Oregon, where he completed his residency.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Photodynamic Therapy & Actinic Keratoses

What is the best way to treat actinic keratoses?

Overall, combination treatments using one or two types of therapies are best. For example, a good program may be to freeze the individual thick AKs with liquid nitrogen, allow them to heal for two to three weeks, and then treat the entire area with a field treatment like fluorouracil (Efudex) or photodynamic therapy.

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Cancer 101 Pictures Slideshow: A Visual Guide to Understanding Cancer

What is photodynamic therapy (PDT)?

Photodynamic therapy (PDT) is a medical treatment that utilizes a photosensitizing molecule (frequently a drug that becomes activated by light exposure) and a light source to activate the applied drug. Very thin superficial skin cancers called actinic keratoses and certain other types of cancer cells can be eliminated this way. Acne can also be treated as well. 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. Occasionally, a photosensitizing molecule that is already part of the body can be activated. 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 new, evolving science. Current PDT involves a variety of incubation times for different the light-sensitizing drugs and a variety of light sources depending on the target tissue. The basic premise of PDT is selective tissue destruction.

At present, the primary limitation of available PDT technology for skin is the depth of penetration of the light and ability to target cells within 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 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)
Levulan stick (photosensitizer medication)

In dermatology, PDT with the photosensitizer Levulan Kerastick (20% delta-aminolevulinic acid HCl) is used for the treatment of very early, thin skin cancers called actinic keratoses (AK). The initial approval was specifically for the treatment of actinic keratosis of the face and scalp with application of the photosensitizer followed by a timed exposure to a special blue light source. PDT is also used for acne, rosacea, thin nonmelanoma skin cancers, sun damage, enlarged sebaceous glands, wrinkles, warts, hidradenitis suppurativa, psoriasis, and many other skin conditions. It is not used to remove moles or birthmarks.

Application of Levulan to the face
Application of Levulan to the face

Medically Reviewed by a Doctor on 2/19/2016

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