Photodynamic Therapy (PDT)

Penn radiation oncologists and other cancer specialists are experienced in using light-sensitive medication together with low-level beams of light to destroy cancer cells. The Abramson Cancer Center was the first institution in the Delaware Valley with this technology.

Photodynamic Therapy, also known as photoradiation therapy, phototherapy, or photochemotherapy is used to treat certain types of cancer. It is based on the discovery that certain chemicals known as photosensitizing agents can kill organisms when they are exposed to a particular type of light. PDT destroys cancer cells through the use of a fixed-frequency laser light (an intense narrow beam of light) in combination with a photosensitizing agent.


  • The photosensitizing agent is injected into the bloodstream and absorbed by cells all over the body.
  • The agent remains in cancer cells for a longer time than it does in normal cells.
  • When the treated cancer cells are exposed to laser light, the photosensitizing agent absorbs the light and produces an active form of oxygen that destroys the treated cancer cells.
  • The laser light used in PDT can be directed through a fiber-optic (a very thin glass strand). The fiber-optic is placed close to the cancer to deliver the proper amount of light. The fiber-optic can be directed through a bronchoscope into the lungs for the treatment of lung cancer or through an endoscope into the esophagus for the treatment of esophageal cancer.
  • Light exposure must be timed carefully so that it occurs when most of the photosensitizing agent has left healthy cells but is still present in the cancer cells.

An advantage of PDT is that it causes minimal damage to healthy tissue.

However, because the laser light currently in use cannot pass through more than about 3 centimeters of tissue (a little more than one and an eighth inch), PDT is mainly used to treat tumors on or just under the skin or on the lining of internal organs.

Learn more about Photodynamic Therapy at OncoLink.