Photodynamictherapy (PDT) is a treatment that uses a drug, called a photosensitizer or photosensitizing agent, and a particular type of light. When photosensitizers are exposed to a specific wavelength of light, they produce a form of oxygen that kills nearby cells.
Each photosensitizer is activated by light of a specific wavelength. This wavelength determines how far the light can travel into the body. Thus, doctors use specific photosensitizers and wavelengths of light to treat different areas of the body with PDT.
In the first step of PDT for cancer treatment, a photosensitizing agent is injected into the bloodstream. The agent is absorbed by cells all over the body but stays in cancer cells longer than it does in normal cells. Approximately 24 to 72 hours after injection, when most of the agent has left normal cells but remains in cancer cells, the tumor is exposed to light. This is performed in some patients by using a laser beam. The photosensitizer in the tumor absorbs the light and produces an active form of oxygen that destroys nearby cancer cells.
PDT may have promise in treating mucosal dysplasia and small head and neck tumors. Several multi-institutional phase II clinical trials evaluating PDT treatment of head and neck cancers have demonstrated the efficacy of this minimally invasive therapy in the treatment of early oropharyngeal primary and recurrent cancers as well as the palliative treatment of refractory head and neck cancers.
PDT was found as effective as conventional therapies for the treatment of early (carcinoma in situ, T1, T2) squamous cell cancers of the head and neck. It is also a promising therapy to be used in association with surgery to increase tumor-free margins and therefore increase cure rates.