Photodynamic Therapy (PDT)
Photodynamic therapy (PDT) uses light-activated medicines to kill cancer cells. Learn more about how PDT works, its benefits and limitations, and possible side effects.
What is photodynamic therapy?
Photodynamic therapy (PDT) is a treatment that uses special medicines along with light to kill cancer cells. These medicines are sometimes called photosensitizing agents. They only work after they are activated or “turned on” by certain kinds of light.
You might also hear PDT called photoradiation therapy, phototherapy, or photochemotherapy.
How does PDT work?
During PDT, a photosensitizing agent is either put on your skin or into your bloodstream through a vein. How the medicine is given depends on the part of your body being treated.
Over a certain amount of time, the cancer cells absorb the medicine. Then, light is applied to the area being treated.
- The light causes the medicine to react and form a special kind of oxygen molecule that kills the cells.
- PDT might also help by destroying the blood vessels that feed the cancer cells and by alerting your immune system to attack the cancer.
PDT is usually done as an outpatient procedure (meaning you won't have to stay in the hospital). Sometimes it is combined with surgery, chemotherapy (chemo) or other anti-cancer treatments, or radiation therapy.
What kind of light is used?
The light used in PDT comes from special lasers or light-emitting diodes (LEDs). The kind of light used depends on the type of cancer and where it is located.
How long does it take?
The period of time between when the medicine is given and when the light is applied is called the drug-to-light interval. It can be anywhere from a couple of hours to a couple of days. This depends on the medicine used.
What is PDT used for?
PDT may be used to treat:
- Pre-cancers of the skin
- Basal cell skin cancer
- Early-stage squamous cell skin cancer
- Esophageal cancer
- Cutaneous T-cell lymphoma
- Non-small cell lung cancer
It may also be used to relieve symptoms if cancer has spread and is blocking an airway.
There are other off-label uses for PDT, so your health care team may discuss these with you.
PDT medicines approved in the US to treat cancer
Several photosensitizing agents are currently approved by the US Food and Drug Administration (FDA) to treat certain cancers or pre-cancers.
Two of the most widely used PDT medicines are:
- Porfimer sodium (Photofrin): A very widely used and studied photosensitizer, activated by red light from a laser. It’s approved by the FDA to treat certain kinds of cancers of the esophagus and lung. It is also being studied in other types of cancer.
- Aminolevulinic acid (ALA or Levulan): This medicine is put right on your skin, only on the face or scalp. It is used to treat actinic keratosis (AK), a skin condition that can become cancer. A special blue light (not a laser) is used to activate this medicine.
Experts are always looking for new PDT medicines and new ways to give them. They are also looking at combining PDT with other types of treatment, such as surgery, chemo, immunotherapy, and radiation therapy.
More research is needed to see what other cancers may benefit from PDT.
Side effects of PDT
Not everyone getting PDT has the same side effects. Ask your health care team which side effects you might have and what can be done to help or treat them.
Also ask if there are any side effects you need to report right away. Get the phone number to call if you have problems outside regular office hours.
Photosensitivity reactions
The most common side effect of PDT is sensitivity to bright lights and sunlight. These reactions can show up on the skin where the medicine is applied. They usually involve redness and a tingling or burning sensation.
For a period of time after treatment, you'll need to be careful not to expose treated areas to light.
- Stay out of strong, direct light.
- Stay indoors as much as possible.
- Wear protective clothing and wide-brimmed hats to avoid sunlight when outdoors.
- Avoid beaches, snow, light-colored concrete, or other surfaces where strong light may be reflected.
Sunscreen will not protect your skin from photosensitivity reactions.
Skin problems
Skin problems that may happen after PDT treatment include:
- Redness and swelling
- Blisters
- Burning or itching sensation
- Color changes (more common in darker skin tones)
- Cold sore flare-ups
- Contact allergy (skin irritation after contact with something you are allergic to)
Eye damage
You can get eye damage if you look into the blue light or laser light. Your care team will give you eye protection to prevent this.
Swelling and pain
Some people get swelling in the treated area. This can lead to pain and problems with the tissues and organs working properly. Pain may be experienced at different times during PDT therapy. It varies from person to person.
Options to manage pain may include:
- A nerve block
- Cool air or compresses
- Topical or local injections of pain medications, like Lidocaine
- Topical steroids
- Changes to the type of PDT given
Talk to your health care team about ways to manage your pain.
Immune system changes
PDT treatments may affect how your immune system works, usually by stimulating it to work more.
Sometimes, your immune system can become weaker for period of time. In very rare cases, PDT can cause skin cancer at the site where treatment was given. Some experts believe this happens if the immune system is weakened by PDT.
Benefits and limitations of PDT
Studies have shown that PDT can work as well as surgery or radiation therapy in treating certain kinds of cancers and pre-cancers.
There are some benefits of PDT:
- Long-term side effects are rare when used properly
- Less invasive than surgery
- Usually quick and done as an outpatient procedure
- Can be targeted very precisely
- Can be repeated many times at the same site if needed (unlike radiation)
- Usually little or no scarring after the site heals
- Often costs less than other cancer treatments
But PDT has limitations, too:
- PDT can only treat areas where light reaches, so it’s mainly used to treat problems on or just under the skin, or in the lining of organs that can be reached with light.
- Light can’t travel very far through body tissues, so PDT can’t treat large cancers or cancers that have grown deep into the skin or other organs.
- It can’t treat cancers that have spread to many places.
- It can’t be used in people with certain blood diseases.
- PDT medicines cause light sensitivity for some time, so special precautions must be taken.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
American Society of Clinical Oncology. Skin cancer (non-melanoma): Types of treatment. Cancer.net. Content is no longer available.
Maytin, EV, Warren, CB. Photodynamic therapy. UpToDate. 2024. Accessed at https://www.uptodate.com/contents/photodynamic-therapy on April 9, 2025.
National Cancer Institute (NCI). Photodynamic therapy. Update June 21, 2021. Accessed at https://www.cancer.gov/about-cancer/treatment/types/photodynamic-therapy on April 9, 2025.
Last Revised: May 30, 2025
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
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