Photodynamic Therapy

Photodynamic therapy uses a photosensitizing agent with light exposure to target and kill cancer cells.

Key Points

  • 1

    Photodynamic therapy uses light to create singlet oxygen to attack cancerous cells.

  • 2

    This treatment is administered over the course of several days.

  • 3

    Photodynamic therapy is relatively painless with few potential side effects.

  • 4

    The therapy has shown some success in other cancers, but is still in its early stages.

As cancer research broadens and scientists continue to explore new treatment avenues, patients can take advantage of a wide variety of treatments for deadly diseases like mesothelioma, instead of relying only on traditional therapies like radiation and chemotherapy.

Photodynamic therapy is one of those treatments that shows much promise in treating particular kinds of cancer, and is sometimes recommended for those who have mesothelioma.

How Photodynamic Therapy Works?

Photodynamic therapy (PDT), also known as photochemotherapy, exposes light-sensitive compounds to light, causing them to become toxic and target diseased cells, such as malignant cancer cells and other abnormal cells, as well as microbes such as certain forms of fungi, bacteria, and viruses.

3 Things PDT Needs to Work
  1. A light source
  2. Oxygen (in the tissue)
  3. A photosensitizing agent (porphyrin, chlorophyll or dye)

When the photosensitizing agent is exposed to a certain wavelength of light, it produces singlet oxygen – a form of oxygen with much higher energy levels than the form of oxygen people breathe in the open air (triplet oxygen). Due to its high energy level, the singlet oxygen is more reactive and will kill nearby cancer cells. Different photosensitizers and different wavelengths are used depending on the part of the body and the type of cancer being treated.

Photodynamic therapy can also aid mesothelioma patients in that it can shrink or destroy tumors by damaging the blood vessels that feed the tumor, thereby depriving it of nutrients necessary for growth. Some researchers believe that PDT may help activate the immune system.

What to Expect

Photodynamic therapy is administered in two steps. First, the photosensitizing agent is injected into the bloodstream of the cancer patient. It is absorbed by all the body’s cells but remains in cancer cells for a longer period of time. In about 2 to 3 days, the patient returns to the outpatient facility and the tumor is exposed to a laser light using a thin fiber optic glass strand. The light is applied for 5 to 45 minutes, depending on the size of the tumor. Any dead tissue is later removed through an endoscopic procedure, usually about 5 days later.

Treatment with photodynamic therapy is painless and side effects are minimal. Swelling may occur in the area to which the light was applied and photosensitize reactions may occur, including severe sensitivity to light. Patients should avoid bright light and direct sunlight and should limit their time outdoors for the first 30 days after the treatment is administered.

Does PDT Work?

Currently, PDT is being used to treat esophageal, non-small cell lung cancers (NSCLC), mesothelioma, and some skin cancers. Some success is apparent.

Trials are underway to determine the success of photodynamic therapy success in treating other cancers. Newer photosensitizing agents are being developed in hopes of reaching tumors deeper under the skin. Scientists are also working on PDT drugs that can better target specific cancer cells.

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Written By Tonya Nelson Tonya Nelson

Tonya Nelson is an experienced writer and editor, who has published on a wide variety of topics, particularly in the health field. Her bachelor’s degree in magazine journalism from the S.I. Newhouse School of Public Communications at Syracuse University sparked her curiosity for writing stories about environmental and medical issues. As the Managing Editor, Tonya oversees the content development process, ensuring every article and informational page published adheres to MAA Center’s editorial guidelines.