13 april 2011: ik ben kanker-actueel aan het herzien en laat onderstaand artikel staan omdat PDT - Photo Dynamische Therapie meer en meer wordt toegepast bij slokdarmkanker. O.a. in het AvL - Amsterdam en Erasmus Medisch Centrum wordt PDT toegepast bij hoofd- halstumoren, waaronder slokdarmkanker
In het Medisch Centrum van Maryland melden artsen dat ze opmerkelijke successen boeken met nieuwe lichtgevoeligere fotosensitizers bij PDT bij mond - en keel/slokdarmkanker.
Laser Light Therapy Seen As "Magic Bullet" For Treating Some Throat And Oral Cancers
Photodynamic therapy, which uses a red laser and a light-sensitive drug to destroy cancer cells without harming normal tissue, represents a promising new treatment option for patients with throat or oral cancers, according to a voice and swallowing specialist at the University of Maryland Medical Center.
"It's as close to a magic bullet as you can get to kill cancers that are close to the surface," says Paul F. Castellanos, M.D., an otolaryngologist/head and neck surgeon who has treated a dozen patients with the minimally invasive laser light therapy in the past 18 months. Nine of those patients had throat cancer, and three had oral cancer.
"Photodynamic therapy is the only thing that kills the cancerous tissue and the precancerous tissue, but not the normal tissue," says Dr. Castellanos, who is also an assistant professor of surgery at the University of Maryland School of Medicine. "We are very excited about this new frontier in the treatment of these kinds of cancers and premalignancies."
Before patients receive the therapy, they are given an intravenous injection of a light-sensitive drug called porfimer sodium, which passes through normal cells but collects in cancerous and precancerous cells. Two or three days after the injection, doctors expose those areas to a red laser, causing a chemical reaction that destroys the diseased cells.
Other lasers kill cancer cells with heat?vaporizing or cutting out tumors, along with a portion of the surrounding healthy tissue. In photodynamic therapy, the red laser's concentrated beam of light activates the Photofrin to produce a toxic form of oxygen that kills the cancer cells without harming the adjacent tissue.
The procedure is performed in the operating room while patients are under anesthesia. In treating throat cancer, Dr. Castellanos uses a device called a laryngoscope to get a clear view of the patient's throat and larynx. He then threads a thin fiber-optic conduit through the scope to deliver the laser beam directly to the cancer. The treatment lasts about nine minutes, and patients go home the same day.
Patients may experience some soreness or redness in the area that was exposed to the light, but the major side effect is sensitivity to direct sunlight. The photoactive drug lingers in the cells of the skin and eyes, and those who have been treated must stay out of the sun for about six weeks.
"The photosensitivity is a big nuisance. But it's nothing that time out of the sun won't remedy," Dr. Castellanos says, adding that sunscreen doesn't protect patients because it only blocks ultraviolet rays, not red light from the sun. He advises patients to cover themselves completely and wear sunglasses or to venture outside only after dusk during the time they are light-sensitive. He says that standard treatments for throat and oral cancer, such as surgery and radiation, carry more risks and can have more serious and longer-lasting side effects. For example, six weeks of radiation therapy for throat cancer can cause a drying or stiffening of the vocal cords, reducing voice quality. The tumor can also be replaced by scar tissue, which would also affect the voice.
The laser therapy is most effective for cancers that are close to the surface or precancerous conditions because the red laser only penetrates a quarter of an inch, Dr. Castellanos says. But he notes that patients can be treated again within one or two weeks to remove deeper tumors. "Patients can also receive other forms of treatment, such as surgery or radiation, if their cancer does not respond to this therapy. It does not eliminate any options," he says, adding that only two of the 12 patients treated so far have needed further therapy because their cancers were more advanced.
Dr. Castellanos says that the procedure has been used successfully for late-stage or inoperable cancers and in combination with other treatments such as chemotherapy or radiation.
The U.S. Food and Drug Administration has approved photodynamic therapy to treat esophageal cancer, lung cancer and a precancerous skin condition known as actinic keratosis, but researchers have reported encouraging results in treating other cancers as well. In clinical studies of more than 350 people with early-stage cancers of the mouth, throat and larynx, 88 percent of the patients showed no evidence of the disease after the first treatment.
"We started using photodynamic therapy to treat throat and oral cancers a year and a half ago, and so far, we have had excellent results," Dr. Castellanos says. "Based on the literature and our experience, it is as effective or in some cases even more effective than the other treatments." And the treatment may become more useful for a broader range of cancers as researchers look for ways to increase the depth the laser can penetrate, test other photosensitive drugs and try to reduce the photosensitivity side effects, Dr. Castellanos says.
Photodynamic therapy is also used by Bruce D. Greenwald, M.D., a gastroenterologist at the
University of Maryland Greenebaum Cancer Center and an associate professor of medicine at the University of Maryland School of Medicine, to treat esophageal cancer. Robert A. Ord, M.D., D.D.S., the head of the division of oral-maxillofacial surgery at the medical center and a professor at the University of Maryland Dental School, has also collaborated with Dr. Castellanos to treat patients with oral cancers.
The University of Maryland Medical Center recently opened the Center for Voice, Swallowing and Esophageal Disorders, combining the specialties of otolaryngology, gastroenterology and general and thoracic surgery to treat a broad range of diseases, including cancer. A focus of the new center is to help diagnose and treat voice problems experienced by broadcasters, singers and others who use their voices professionally.
Dr. Castellanos and George Fantry, M.D., director of clinical gastroenterology at the Medical Center and an associate professor of medicine at the University of Maryland School of Medicine, are co-directors of the center.