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News Archive - Progress Newsletter Spring 2000 Online

Research Roundup

Photodynamic Therapy

An outpatient procedure that lasts 20 minutes and removes cancer painlessly? This unlikely sounding scenario may be a reality for qualified lung and esophageal cancer patients thanks to photodynamic therapy (PDT).

Photodynamic therapy uses a drug combined with a laser to destroy cancer

"Photodynamic therapy uses a drug combined with a laser to destroy cancer. It affects drug-treated, cancerous tissue with a much smaller effect on normal tissue. It has dramatic results, clearing up tumors quickly. Although it is not a cure for most people, it does allow them to breathe and swallow easier," says Mark Iannettoni, M.D., associate professor of general thoracic surgery and member of the Thoracic Oncology Clinic at the U-M Cancer Center.

Patients who are eligible for treatment with PDT typically have inoperable lung or esophageal cancer located in the breathing (bronchial tubes) or swallowing passages. During PDT, the patient first receives an intravenous injection of porfimer sodium, a light-activated drug that concentrates in tumor cells. A surgeon then passes an endoscope with a laser light into the patient's airway or esophagus. The laser focuses on the tumor, which causes the porfimer sodium to react and destroy the cells. Tissue is either sloughed off by itself or removed with the endoscope at a second endoscopy.

PDT works much the way photosynthesis does in plants, by using light to spark a chemical reaction. The drug, which the FDA has approved for this use, is inactive until triggered by light. When the light is emitted it causes the drug to produce an unstable form of oxygen, which makes the cancerous tissue inflame and detach.

"PDT is much less invasive than surgery," explains Dr. Iannettoni. "The treatment lasts 15 to 20 minutes and there is no inpatient hospital stay required and no wound produced that needs to be healed."

The use of photodynamic therapy in the United States is restricted -- now only approved for esophageal cancer and for early-stage lung cancer in patients who have no treatment alternatives.

"Photodynamic therapy is most effective in treating early or late-stage cancers," says Dr. Iannettoni. "It is especially effective for people with esophageal and airway tumors. A person who undergoes this therapy will be breathing better one to two days after the procedure and swallowing improves within a week."

The major side effect to photodynamic therapy is that patients are photosensitive for approximately four weeks after injection. This means that they must not go outside, for risk of sunlight exposure, without being completely covered up and must stay away from bright flourescent lights. Most patients are willing to tolerate this side effect if it means gaining a drastic improvement in their condition.

Doctors warn that light therapy is by no means a replacement for standard treatments. Unlike chemotherapy, PDT cannot attack cancer cells that have spread throughout the body, since it works by targeting tumors. It is also not useful on bloodborne cancers such as leukemia. And because light waves cannot penetrate more than several millimeters of tissue, deeply lodged tumors are inaccessible to PDT.

Photodynamic therapy is a promising treatment that may have wider use in the future. "PDT may have application in treating some breast and head and neck cancers in the future," asserts Dr. Iannettoni. "Hopefully one day U-M will have a treatment center just for photodynamic therapy."

 

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