In photodynamic therapy (PDT), a nontoxic chemical injected into the blood collects in the tumor for a few days. A laser light is then focused on the tumor, causing changes in the injected chemical. The light transforms the nontoxic chemical into a new one that kills cancer cells.
PDT can destroy cancer cells while causing little damage to normal cells. The chemical, however, needs light to be activated. This limits its reach to those cancers near the inner surface of the esophagus, which can be reached by the special light passing through the endoscope. This light cannot reach those cancers that are deep within the esophagus or other organs.
Preliminary studies have shown PDT to cure some early-stage esophageal cancers that have not yet spread to deeper tissues. In these studies, however, the length of follow-up time was short.
In cases where PDT is being used as curative treatment, doctors must ascertain that the cancer has not spread deeper. For the moment, Barrett’s esophagus and very early cancers are the main cases where PDT is being used.
Nonetheless, PDT can be a palliative treatment, particularly in cancers that block the esophagus and have returned following radiation therapy. As a palliative measure, PDT will not kill all the cancer, but it will destroy enough cancer cells thus improving the patient’s ability to swallow.
PDT may lead to side effects that could be severe and long-lasting. They include sensitivity to the sun and other light sources, and discoloration or redness of the skin. These conditions may make it necessary for patients to stay indoors for up to six weeks following treatment.
The exact role that PDT could play in the treatment of cancer is still being evaluated, particular when its results are compared with those of other treatments such as surgery and the use of lasers.
Studies are also being undertaken to explore ways of improving PDT. These studies have to do with developing new photosensitizing drugs and finding ways of delivering the proper amount of light to the cancer.
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Reviewed by:
Jiade J. Lu, M.D.
Diplomate, American Board of Radiology (Radiation Oncology)
Medical Director
The Cancer Information Network
Date Modified: 06/10/04
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