Photodynamic Therapy
(PDT or Blue Light Therapy)

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What is photodynamic therapy (PDT)?

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. Very thin superficial skin cancers called actinic keratoses and certain other types of cancer cells can be eliminated 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. Then light energy is applied selectively to the appropriate tissue.

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)
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 a combination of an application of the photosensitizer followed by a timed exposure to a special 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
Application of Levulan to the face
Medically Reviewed by a Doctor on 7/30/2012

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Photodynamic Therapy - Experience Question: For what condition did you have photodynamic therapy?
Photodynamic Therapy - Skin Question: For what condition(s) did you seek photodynamic therapy?

Does PDT have any complications or side effects?

Porfimer sodium makes the skin and eyes sensitive to light for approximately 6 weeks after treatment. Thus, patients are advised to avoid direct sunlight and bright indoor light for at least 6 weeks.

Photosensitizers tend to build up in tumors and the activating light is focused on the tumor. As a result, damage to healthy tissue is minimal. However, PDT can cause burns, swelling, pain, and scarring in nearby healthy tissue. Other side effects of PDT are related to the area that is treated. They can include coughing, trouble swallowing, stomach pain, painful breathing, or shortness of breath; these side effects are usually temporary.

SOURCE:

National Cancer Institute


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