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Definition

Photodynamic therapy (PDT) uses a medicine together with a special type of light to kill cancer cells.

How Photodynamic Therapy Works

First, the health care provider injects a medicine that is absorbed by cells all over the body. The medicine stays in cancer cells longer than it stays in normal, healthy cells.

After 1 to 3 days, the medicine is gone from the healthy cells, but remains in the cancer cells. Then, the provider directs light at the cancer cells using a laser or other light source. The light triggers the medicine to produce a type of oxygen that treats cancer by:

• Killing cancer cells
• Damaging blood cells in the tumor
• Helping the body's infection-fighting system attack the tumor

The light can come from a laser or other source. The light is often applied through a thin, lighted tube that is put inside the body. Small fibers at the end of the tube direct the light at the cancer cells. PDT treats cancer in the:

• Lungs, using a bronchoscope
• Esophagus, using upper endoscopy

Providers use light-emitting diodes (LEDs) to treat skin cancers. Medicine is placed on the skin, and the light is shone on the skin.

Another type of PDT uses a machine to collect a person's blood, which is then treated with a medicine and exposed to light. Then, the blood is returned to the person. This is used to treat symptoms of a certain type of lymphoma.

Pros and Cons of PDT

PDT has several benefits. For example, it:

• Targets only cancer cells, not normal cells
• Can be repeated many times in the same area, unlike radiation therapy
• Is less risky than surgery
• Takes less time and costs less than many other cancer treatments

But PDT also has drawbacks. It can only treat areas where light can reach. That means it can only be used to treat cancer on or just under the skin, or in the linings of some organs. Also, it cannot be used in people with certain blood diseases.

Side Effects of PDT

There are two main side effects of PDT. One is a reaction caused by light that makes the skin swollen, sunburned, or blistered after just a few minutes in the sun or near bright lights. This reaction can last as long as 3 months after treatment. To avoid it:

• Close the shades and curtains on windows and skylights in your home before you get your treatment.
• Bring dark sunglasses, gloves, a wide-brimmed hat, and wear clothes that cover as much of your skin as possible to your treatment.
• For at least a month after treatment, stay inside as much as possible, especially between 10 a.m. and 4 p.m.
• Cover your skin whenever you go outside, even on cloudy days and in the car. Do not count on sunscreen, it will not prevent the reaction.
• Do not use reading lamps and avoid exam lamps, such as the type a dentist uses.
• Do not use helmet-type hair dryers like those in hair salons. Use only the low heat setting when using a hand-held hair dryer.

The other main side effect is swelling, which may cause pain or trouble breathing or swallowing. These depend on the area that is treated. The side effects are temporary.

References

American Cancer Society website. Getting photodynamic therapy. www.cancer.org/treatment/treatments-and-side-effects/treatment-types/radiation/photodynamic-therapy.html. Updated November 19, 2021. Accessed April 2, 2024.

Lui H, Kalia S. Photodynamic therapy. In: Bolognia JL, Schaffer JV, Cerroni L, eds. Dermatology. 5th ed. Philadelphia, PA: Elsevier; 2025:chap 135.

National Cancer Institute website. Photodynamic therapy to treat cancer. www.cancer.gov/about-cancer/treatment/types/photodynamic-therapy. Updated June 21, 2021. Accessed April 2, 2024.

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