Photodynamic therapy (PDT) is a cancer treatment method that uses medicines called photosensitizing agents and a light source to cause a chemical reaction lethal to cancer cells. When compared to other treatments, photodynamic therapy for cancer is less invasive, has no long-term side effects or scarring, is precise in targeting only cancer cells, and is generally less expensive. Additional advantages are that it can be done on an outpatient basis, and allows for rapid recovery and the repetition of treatments on the same site if necessary. The main disadvantage is that the treatment is limited to areas of the body that can be exposed to light, such as the skin and the linings of internal organs. Other disadvantages include extreme light sensitivity for a period of time after the treatments and swelling at the treatment site.
The advantages of photodynamic therapy for cancer include the speed of the patient’s recovery and the minimally invasive nature of the treatment. Patients are given special drugs called photosensitizing agents that target the more metabolically active cancer cells. Although healthy cells also absorb the drug, they rid themselves of the medicine quickly and are not affected by it. A source of light, usually low-energy laser light, is applied to the cancer cells, and reacts with the photosensitizing agent to cause the death of the cancer cells. Healthy tissues and cells are not affected by the therapy, which is usually done as an outpatient since recovery is rapid.
Photodynamic therapy targets the cancer cells precisely with little or no damage to other tissues, greatly reducing side effects as well as recovery time. Along with killing cancer cells, a further advantage is that it also reduces the blood vessels that feed them. Unlike radiation therapy, photodynamic therapy can be used repeatedly at the same site if necessary. It is also used effectively in conjunction with other cancer therapies. This therapy is also generally less expensive than other therapies.
The primary disadvantage of photodynamic therapy for cancer is the limitation of its use to regions that can be exposed to light. Low-energy laser light cannot penetrate into tissues deeper than about 1/3 of an inch (8.46 mm). Large tumors and cancers that have metastasized generally are not treated with photodynamic therapy due to the inability of the light source to penetrate large tumors or reach areas where cancer may have spread. Photodynamic therapy is effectively used for skin cancer and cancers of the esophagus and lungs.
Side effects from photodynamic therapy for cancer are generally mild and short-term. The main post-treatment precaution involves protecting the skin and eyes from sunlight and strong indoor lights. While preparing for this therapy, patients should darken the home, pulling blinds and curtains, and take sunglasses, a wide-brimmed hat, and tightly woven clothing that covers all skin with them to their therapy. Depending on the type of photosensitizing agents used, increased sensitivity to light can occur for up to several months after photodynamic therapy.