Wouldn’t it be great if light could kill cancer cells? In some cases, it can.
Photodynamic therapy for cancer, also referred to as PDT, combines a drug called a photosensitizer or photosensitizing agent and a specific wavelength of light, reports the National Cancer Institute. The combination produces a specific form of oxygen that kills nearby cancer cells.
How It Works
First, the photosensitizing agent must be either applied to the skin or given by IV into the bloodstream. Cells all over the body absorb the agent, but it stays longer in cancer cells than other types of cells. Within one to three days, most of the photosensitizer will have left the healthy cells but not the cancer cells. This sets them up as targets.
Once that happens, the physician uses a precisely targeted laser to activate or “turn on” the treatment. According to the American Cancer Society, the laser’s light causes the drug to react with oxygen. The oxygen-drug mixture then forms a chemical that kills the cells. Scientists also believe that photodynamic therapy works by destroying cancer-feeding blood vessels. It might also stimulate the immune system to attack the cancer cells.
What Kinds of Cancer Can It Treat?
To date, the U.S. Food and Drug Administration (FDA) has approved PDT to treat esophageal cancer and to relieve its symptoms when the cancer makes swallowing difficult or impossible. Photodynamic therapy is also approved to treat non-small cell lung cancer when other treatments haven’t worked and for symptom relief in patients whose cancer is blocking their airways.
Photodynamic therapy is also used to fight the severe skin symptoms that can occur with cutaneous T-cell lymphoma that isn’t responding to other therapies. It may even help against two precancerous conditions: Barrett’s esophagus and actinic keratosis on the skin, says the American Cancer Society and a study published in Health Technology Assessment.
Pros and Cons
Most patients tolerate photodynamic therapy for cancer well. It’s less invasive than surgery, generally performed on an outpatient basis and can be repeated as needed. The careful, precise targeting of the laser used in photodynamic therapy means side effects are minimal.
Unfortunately, PDT can only be used on localized cancers. Once cancer has spread or metastasized, PDT is no longer an option. Additionally, the American Cancer Society points out that photodynamic therapy can only treat areas where light can reach. Thus, PDT’s best targets are tumors on your skin or just underneath it or in areas of your body that can be reached using a light source. That means PDT for Barrett’s esophagus or esophageal cancer, the doctor will use an endoscope to deliver the necessary light inside your throat. For non-small cell lung cancer, the doctor will use a bronchoscope to direct the light inside your lungs.
Avoid the Sun
PDT leaves your eyes and skin sensitive to light for several weeks following treatment. Sunburn, swelling and blistering can occur within minutes of sun exposure. People who have been treated with photodynamic therapy for cancer will need to take precautions to protect themselves against photosensitivity reactions. These include wearing sunglasses and a wide-brimmed hat, keeping skin covered at all times and staying indoors during daylight hours when possible.
And be aware that sunscreens protect only against ultraviolet light. It won’t prevent photosensitivity reactions, so be extra diligent.
Many scientists are looking at ways to improve PDT. These include investigating other light sources and developing new photosensitizing drugs that might allow for deeper treatments or work more quickly and efficiently. Additionally, PDT is being studied as a potential therapy for other types of cancers, too. These include cancers of the skin, brain, head and neck, oral cavity, stomach and other digestive organs and sex organs like the prostate or cervix.
UVA Cancer Center offers photodynamic therapy to treat esophageal and non-small lung cancer.Learn More