Related Document: Photodynamic Therapy.pdf (Reprinted with permission
from the Messenger-Inquirer)
Article highlights photodynamic therapy through the experiences of patients.
While growing up, summertime for Carla Payne meant being outdoors. "If the sun was shining, my mother put us out in the yard to play," said Payne, 63, of Maple Heights. Sunscreen was a rarity then and later as a teenager when she hung out with friends at the old Miller's Lake near Moseleyville.
"You're indestructible. You don't think anything is going to happen to you," Payne said. Ten years ago, something did happen to the fair-skinned woman. Red, crusty patches slightly smaller than a pencil eraser popped up two or three at a time on her temples, forehead, arms, legs and back. They were precancerous lesions called actinic keratoses, the earliest stage of skin cancer that shows up on the outer layer of skin because of long-term sun exposure. The spots would be cut or frozen off, leaving semi-circular or half-inch white scars. But in May, she underwent three sessions of photodynamic therapy, a relatively new treatment using light to activate a topical lotion that kills precancerous cells in most cases.
"I could tell the next week my face looked...smoother," Payne said of the first treatment by Dr. Michael Crowe at Owensboro Dermatology. The procedure also has been used to treat acne, and early data have dermatologists thinking it could prevent pre-skin cancers. If so, "then we've entered a whole new era," said Dr. Michael Gold, a Nashville dermatologist who took part in the original clinical trials of the topical lotion. More data won't be in until the end of the year, but patients from five years ago have very few, if any, recurrences of pre-skin cancers, Gold said.
"Photodynamic therapy is progressing into this unknown world we're trying to define," Gold said Friday in a phone interview. "This is one of the most intriguing new therapies we've had in years."
How it works:
The process came to the United States from Europe in the late 1990s, Gold said. In 2000, the federal Food and Drug Administration approved the lotion, which contains the only photosensitizer available in the United States, he said. It is marketed under the brand name Levalen Kerastick by Boson-based (Levulan Kerastick by Boston-based) DUSA Pharmaceuticals Inc., for which Gold is a consultant. The lotion is applied to the patient's face 30 minutes to an hour before treatment. A laser, LED or intense pulse light is then shown on the treated area. The length and intensity of exposure depends on the patient's condition. Once exposed, the body converts the lotion to protoporphyrin IX, a photosensitive enzyme. Certain cells - including pre-cancerous ones and those in sebaceous glands where acne forms - absorb the enzyme. In the presence of light and oxygen, "it selectively gets destroyed...and it takes with it what's there" leaving normal cells undamaged, Gold said.
Dermatologist Dr. Trey Truett likens it to a smart bomb hitting the cellular structure of the damaged cells. "When the light hits it, it's kind of like throwing a wrench into the machinery," said Truett with Owensboro Dermatology, which has treated 50 patients since it started using the therapy in January.
"What we know is, if you do that, about 90 percent of the pre-skin cancers disappear," Gold said. Photodynamic therapy leaves patients sensitive to sunlight for 24 to 36 hours after a treatment, so they must stay indoors.
"Those days, I read a good book and just relax," Payne said.
Testing the lotion:
In its infancy, photodynamic therapy required applying the lotion 14 to 18 hours before treatment. "The biggest problem with the treatment was that you got red and crusty at the sites of the lesions, which took up to about a week to heal," Gold said.
The lotion was expensive, and only certain light could be used, Truett said. Later testing showed different lights could be used, the lotion could be made cheaply and patients could have it applied only an hour or so before treatment.
And it still had the same 90 percent success rate, Gold said. Doctors later learned it would smooth skin, so the process is now sometimes used for photo rejuvenation for the whole face, Gold said. In the past two to three years, the process has been used to treat severe to moderate acne. "It works, for some people, miraculously," he said. Studies have shown acne does not recur in most cases, and little maintenance is needed, he added.
Truett said the process also is being used to treat adult acne and wrinkles. All of its uses are done with a minimum of damage, compared with cutting or freezing spots, Truett said. "This is probably the method that is going to give the best cosmetic result," he said.
By David Blackburn
Messenger-Inquirer
