Explore how photodynamic therapy offers a targeted, non-invasive cancer treatment, helping to destroy cancer cells and support overall patient recovery.
Photodynamic therapy (PDT) uses a drug called a photosensitizer together with a specific wavelength of light. When the sensitizer is exposed to this light, it produces a form of oxygen that destroys nearby cells.
Each photosensitizer is activated by a particular wavelength, which determines how deeply the light can travel into the body. Doctors therefore select specific sensitizers and wavelengths to reach the tissue they intend to treat.
First, the photosensitizing agent is injected into the bloodstream. It is taken up by cells throughout the body but remains longer in cancer cells. Twenty-four to seventy-two hours later—after most agent has left normal cells—the tumor is illuminated. The sensitizer absorbs the light and generates reactive oxygen that kills the cancer cells.
Besides direct tumor-cell destruction, PDT may shrink tumors by damaging their blood supply and can trigger an immune response against the cancer.
Light sources include lasers, which can be carried through fiber-optic cables inserted via an endoscope to reach the lungs or esophagus, and light-emitting diodes (LEDs) for surface lesions such as skin cancer.
PDT is usually an outpatient procedure, can be repeated, and may be combined with surgery, radiation, or chemotherapy.
Extracorporeal photopheresis (ECP) is a modified form: blood cells are collected, treated outside the body with a sensitizer and light, then returned to the patient. ECP is FDA-approved to ease skin symptoms of refractory cutaneous T-cell lymphoma; studies are exploring its use in other blood cancers and for transplant rejection.
The FDA has approved porfimer sodium (Photofrin®) for PDT to treat or palliate esophageal cancer and non-small cell lung cancer. It is indicated to relieve obstruction in the esophagus or airways when other measures are inadequate, and to treat Barrett esophagus with high-grade dysplasia.
Activating light penetrates only about one-third of an inch of tissue, so PDT is generally reserved for superficial or lining tumors. It is less effective for bulky tumors and cannot target cancer that has metastasized.
Photodynamic Therapy for Cancer – National Cancer Institute U.S. Food and Drug Administration
Porfimer sodium can make the skin and eyes sensitive to light for roughly six weeks after treatment, so patients are advised to avoid direct sunlight and bright indoor light during this period.
Photosensitizers accumulate mainly in tumors, and the activating light is aimed at the tumor, so damage to healthy tissue is usually limited. Still, PDT may cause burns, swelling, pain, or scarring in nearby normal tissue. Side effects also depend on the site treated and can include coughing, trouble swallowing, stomach pain, painful breathing, or shortness of breath; these effects are generally temporary.
Researchers continue to explore ways to improve PDT and extend its use to other cancers. Clinical trials are under way to evaluate PDT for brain, skin, prostate, cervical, and peritoneal cancers. Work is also focused on developing more powerful photosensitizers that target cancer cells more precisely and can be activated by light that penetrates deeper tissue. Improvements in delivery devices and light sources are being studied as well.
