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Photodynamic Therapy for Cancer: Questions and Answers 

1. What is photodynamic therapy?

Photodynamic therapy (PDT) is a treatment that uses a drug, called a photosensitizer or 

photosensitizing agent, and a particular type of light. When photosensitizers are exposed 

to a specific wavelength of light, they produce a form of oxygen that kills nearby cells 

(1, 2, 3). 

Each photosensitizer is activated by light of a specific wavelength (3, 4). This 

wavelength determines how far the light can travel into the body (3, 5). Thus, doctors 

use specific photosensitizers and wavelengths of light to treat different areas of the body 

with PDT. 

2. How is PDT used to treat cancer? 

In the first step of PDT for cancer treatment, a photosensitizing agent is injected into the 

bloodstream. The agent is absorbed by cells all over the body, but stays in cancer cells 

longer than it does in normal cells. Approximately 24 to 72 hours after injection (1), 

when most of the agent has left normal cells but remains in cancer cells, the tumor is 

Key Points

• Photodynamic therapy (PDT) combines a drug (called a photosensitizer or 

photosensitizing agent) with a specific type of light to kill cancer cells (see 

Questions 1 and 2). 

• The U.S. Food and Drug Administration (FDA) has approved the photosensitizing 

agent called porfimer sodium, or Photofrin®, for use in PDT to treat or relieve the 

symptoms of certain cancers (see Question 3). 

• Patients treated with porfimer sodium should avoid direct sunlight and bright 

indoor light for at least 6 weeks after treatment (see Question 5). 

• Researchers continue to study ways to improve the effectiveness of PDT and 

expand its use to other cancers (see Question 6). 
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exposed to light. The photosensitizer in the tumor absorbs the light and produces an 

active form of oxygen that destroys nearby cancer cells (1, 2, 3). 

In addition to directly killing cancer cells, PDT appears to shrink or destroy tumors in 

two other ways (1, 2, 3, 4). The photosensitizer can damage blood vessels in the tumor, 

thereby preventing the cancer from receiving necessary nutrients. In addition, PDT may 

activate the immune system to attack the tumor cells. 

The light used for PDT can come from a laser or other sources of light (2, 5). Laser light 

can be directed through fiber optic cables (thin fibers that transmit light) to deliver light 

to areas inside the body (2). For example, a fiber optic cable can be inserted through an 

endoscope (a thin, lighted tube used to look at tissues inside the body) into the lungs or 

esophagus to treat cancer in these organs. Other light sources include light-emitting 

diodes (LEDs), which may be used for surface tumors, such as skin cancer (5). 

PDT is usually performed as an outpatient procedure (6). PDT may also be repeated and 

may be used with other therapies, such as surgery, radiation, or chemotherapy (2). 

3. What types of cancer are currently treated with PDT?

To date, the U.S. Food and Drug Administration (FDA) has approved the 

photosensitizing agent called porfimer sodium, or Photofrin®, for use in PDT to treat or 

relieve the symptoms of esophageal cancer and non-small cell lung cancer (7). Porfimer 

sodium is approved to relieve symptoms of esophageal cancer when the cancer obstructs 

the esophagus or when the cancer cannot be satisfactorily treated with laser therapy 

alone. Porfimer sodium is used to treat non-small cell lung cancer in patients for whom 

the usual treatments are not appropriate, and to relieve symptoms in patients with 

non-small cell lung cancer that obstructs the airways. In 2003, the FDA approved 

porfimer sodium for the treatment of precancerous lesions in patients with Barrett’s 

esophagus (a condition that can lead to esophageal cancer) (8). 

4. What are the limitations of PDT?

The light needed to activate most photosensitizers cannot pass through more than about 

one-third of an inch of tissue (1 centimeter). For this reason, PDT is usually used to treat 

tumors on or just under the skin or on the lining of internal organs or cavities (3). PDT is 

also less effective in treating large tumors, because the light cannot pass far into these 

tumors (2, 3, 6). PDT is a local treatment and generally cannot be used to treat cancer 

that has spread (metastasized) (6). 

5. Does PDT have any complications or side effects? 

Porfimer sodium makes the skin and eyes sensitive to light for approximately 6 weeks 

after treatment (1, 3, 6). Thus, patients are advised to avoid direct sunlight and bright 

indoor light for at least 6 weeks. 
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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 (3). 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.

6. What does the future hold for PDT?

Researchers continue to study ways to improve the effectiveness of PDT and expand it to 

other cancers. Clinical trials (research studies) are under way to evaluate the use of PDT 

for cancers of the brain, skin, prostate, cervix, and peritoneal cavity (the space in the 

abdomen that contains the intestines, stomach, and liver). Other research is focused on 

the development of photosensitizers that are more powerful (1), more specifically target 

cancer cells (1, 3, 5), and are activated by light that can penetrate tissue and treat deep or 

large tumors (2). Researchers are also investigating ways to improve equipment (1) and 

the delivery of the activating light (5). 

Selected References 

1. Dolmans DEJGJ, Fukumura D, Jain RK. Photodynamic therapy for cancer. Nature 

Reviews Cancer 2003;3(5):380–387. 

2. Wilson BC. Photodynamic therapy for cancer: Principles. Canadian Journal of 

Gastroenterology 2002;16(6):393–396. 

3. Vrouenraets MB, Visser GWM, Snow GB, van Dongen GAMS. Basic principles, 

applications in oncology and improved selectivity of photodynamic therapy. Anticancer 

Research 2003;23:505–522. 

4. Dougherty TJ, Gomer CJ, Henderson BW, et al. Photodynamic therapy. Journal of the 

National Cancer Institute 1998;90(12):889–905. 

5. Dickson EFG, Goyan RL, Pottier RH. New directions in photodynamic therapy. 

Cellular and Molecular Biology 2003;48(8):939–954. 

6. Capella MAM, Capella LS. A light in multidrug resistance: Photodynamic treatment of 

multidrug-resistant tumors. Journal of Biomedical Science 2003;10:361–366. 

7. U.S. Food and Drug Administration (December 2003). Approved claims for palliative 

line therapy. Retrieved December 29, 2003, from: 

http://www.accessdata.fda.gov/scripts/cder/onctools/linelist.cfm?line=Palliative. 
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8. U.S. Food and Drug Administration (August 2003). FDA approves photofrin for 

treatment of pre-cancerous lesions in Barrett’s esophagus. Retrieved December 29, 

2003, from: http://www.fda.gov/bbs/topics/ANSWERS/2003/ANS01246.html. 

# # # 

Related Resources

Publications (available at http://cancer.gov/publications) 

• National Cancer Institute Fact Sheet 2.11, Clinical Trials: Questions and Answers

• National Cancer Institute Fact Sheet 6.7, Cancer: Questions and Answers

• National Cancer Institute Fact Sheet 6.20, Metastatic Cancer: Questions and 

Answers

National Cancer Institute (NCI) Resources

Cancer Information Service (toll-free)

 Telephone: 1–800–4–CANCER (1–800–422–6237) 

 TTY: 1–800–332–8615 

Online 

NCI’s Web site: http://cancer.gov 

LiveHelp, NCI’s live online assistance: 

https://cissecure.nci.nih.gov/livehelp/welcome.asp 

This fact sheet was reviewed on 5/12/04