Photodynamic Therapy (PDT) uses a drug, called a photosensitizer or photosensitizing agent, and light of a particular wavelength.
When the drug is exposed to that light, it produces a highly reactive form of oxygen that destroys cells nearby. When used as a cancer treatment, the agent is injected into the bloodstream and absorbed by cells all over the body. However, it stays longer in cancer cells. 24 to 72 hours after injection, when the majority of the drug has exited normal cells but is still abundant in cancer cells, the tumor is exposed to the light, and the highly active oxygen produced will only cause an effect within cancerous tissue.
Like NanoKnife therapy, PDT is usually performed as an outpatient procedure, and it can be repeated and combined with other therapies.
However, there are several limitations of Photodynamic Therapy for PCa. The light which is necessary for activation of the drug cannot pass through tissue that is thicker than one-third of an inch, making it not suitable for treatments for the prostate. Additionally, it has been shown to be less effective for the treatment of large tumors.
Disease progression at 24m
Citation for Photodynamic Therapy numbers: Azzouzi, Abdel-Rahmène, et al. "Padeliporfin vascular-targeted photodynamic therapy versus active surveillance in men with low-risk prostate cancer (CLIN1001 PCM301): an open-label, phase 3, randomised controlled trial." The Lancet Oncology 18.2 (2017): 181-191.