Photodynamic therapy (PDT) is a medical treatment for some
types of cancer. PDT uses a combination of laser light of a
specific wavelength, oxygen and a light-sensitive drug to destroy
The light-sensitive drug (the photosensitizing agent) is
injected into the bloodstream and is taken up by the cells
throughout the body. The drug gathers preferentially in cancer
cells, but is not activated until exposed to laser light of the
appropriate wavelength. When a laser is shone onto the cancer, the
drug is triggered to interact with oxygen and form a transitory
substance, known as singlet oxygen, which then destroys the cancer
There is a delay between injection and activation of the drug
using the laser light. The laser light used in PDT is focused
through a fibre-optic, and is shone for only a few minutes. The
doctor holds the fibre-optic very close to the cancer so that the
correct amount of light is delivered. This means that PDT causes
the minimum amount of damage to normal, healthy cells.
In early-stage disease, the aim of treatment with PDT may be to
completely remove and cure the cancer. In advanced disease,
however, the goal may be to shrink the cancer in order to
alleviate symptoms. In this scenario, PDT cannot cure the cancer.
New, normal cells replace those cells killed by PDT allowing
rapid healing to occur post-treatment and avoiding the scarring
disfigurement that may occur with other types of tissue removal.
Even patients who have had surgery, radiotherapy or
chemotherapy in the past can be treatment safely with PDT.