Photodynamic Therapy

Photodynamic therapy (PDT) uses a light-sensitizing drug and a special light to destroy abnormal cells. PDT is useful for treating multiple lesions on the face and scalp.1 PDT is not invasive and it causes little or no scarring.2

PDT is a common treatment for actinic keratosis, an abnormality that can lead to skin cancer. It used to treat Kaposi sarcoma lesions and some low-risk thin non-melanoma skin cancers.3-5

How is photodynamic therapy performed?

Dermatologists perform PDT in their offices. This procedure has two steps, which makes it time consuming. You also may need two treatment sessions that are one week apart, depending on the medication used. Medications approved for PDT for actinic keratosis are:6-8

  • Aminolevulinic acid (brand names: Levulan, Ameluz)
  • Methyl aminolevulinic acid (brand name: Metvixia)

Step 1

The first step is application of the medication. Your dermatologist will prepare the lesion. This may include cleaning the lesion with alcohol. Your doctor may use a curette to scrape the crust or scales of the lesions. A curette is a long, thin instrument with a loop on one end.7,8

Your doctor will apply the light-sensitizing medication to the lesion or lesions. Your doctor may cover the medicated lesions with a bandage or leave them uncovered, depending on the medication.6-8

Step 2

The second step is exposure to strong blue or red light. This step takes place several hours after the medication is applied:6-8

  • Levulan (aminolevulinic acid): Blue light exposure, 14 to 18 hours after medication application.
  • Ameluz (aminolevulinic acid): Red light exposure, 3 hours after medication application.
  • Metvixia (methyl aminolevulinic acid): Red light exposure, 3 hours after medication application.

The light causes the medication to react with oxygen. The result is destruction of the abnormal cells.2

For what types of lesions is photodynamic therapy used?

PDT is used to treat actinic keratosis. Actinic keratosis is a precancer, which forms when cells in the epidermis begin to grow abnormally. Up to 10% of actinic keratoses become squamous cell carcinoma.9 For this reason, your doctor might recommend treating actinic keratoses.

People often have several actinic keratoses. One advantage of PDT is that multiple lesions can be treated at once. PDT may be slightly more effective than cryotherapy for treating lesions.10

PDT is used to treat Kaposi sarcoma lesions.3 It is an alternative to surgery for low-risk thin basal cell carcinoma and squamous cell carcinoma.4,5

What should I expect before, during, and after the procedure?

Because PDT is a two-stage process, the treatment may take a half day or require two visits (one in the afternoon, one the following morning). Between medication application and the light treatment, you must avoid sunlight and bright indoor light.6-8 Wear protective clothing and a scarf or wide-brimmed hat when outside. Sunscreen will not protect the treated skin.6-8 Your skin remains sensitive to light after the procedure. You must stay out of the sun for at least two days after the procedure.6-8 During this time, take extra precautions to protect yourself from sun if you must be outdoors or ride in a car.

During the light treatment, you will wear goggles to protect your eyes from the strong blue or red light. You may feel pain, burning, or stinging during the light treatment. These sensations may last for several hours or a couple days afterward. If you are treated with Metvixia (methyl aminolevulinic acid), you will need a second treatment session 1 week later.8

What are the risks of photodynamic therapy?

Common side effects of PDT are redness, pain, burning, and swelling.6-8 The skin at the treatment site may crust over, change color, itch, or become scaly.1 The treated area may remain red and scaly for up to 4 weeks.2 There are no known long-term side effects of PDT.2

What questions should I ask before photodynamic therapy?

  • What options do I have for treating this lesion?
  • Why do you think PDT is a good option for me?
  • How many appointments and treatment sessions will I need?
  • How long does will the treated area take to heal?
  • How will the treated area look after it heals?
  • How should I protect my skin from the light after treatment? How long will my skin remain extra sensitive to light?
  • How would you re-treat lesions that do not go away after PDT?
  • How often should I have follow-up skin exams?
Written by: Sarah O'Brien | Last reviewed: May 2017.
View References