Photodynamic Therapy
With photodynamic therapy, doctors attempt to use the energy of various wavelengths of light to destroy cancer cells. A chemical will be injected into a patient’s bloodstream that will accumulate in the cancer cells. This chemical may leave normal cells quickly, but stay inside the cancerous cells for up to a month. After the chemical has left the normal tissue, a light source, usually a special laser at a specific wavelength of light, will then be aimed at the cancer. The laser will cause the chemical to release a form of oxygen that is toxic to the cancer cells and will kill them. This is a theoretically good way to treat cancer because it spares normal tissue.At the current time the only chemical approved by the FDA is porfirmer sodium, trademark name Photofrin. It is called a photosensitizing agent. Photosensitizing agents may kill cancer in more ways than just the chemical release activated by light. They may damage blood vessels, and they may also get the immune system to be more active.
This therapy is limited, because the light source can only travel about a centimeter through the skin or other tisue. It can only treat cancer in the lung if it is accessible to the light source. It is approved for use in non-small cell lung cancer and esophageal cancer.
It is being tested for other cancers. It may prove useful in peritoneal mesothelioma, because the light source can be put into the peritoneal cavity.
This therapy has few side effects. Patients must avoid direct sunlight for approximately six weeks after the treatment. The treatment can cause damage to nearby tissue. There are no systemic, serious side effects, so finding a way to use it for other cancers is very important.
Dr. Kaplan