Photodynamic therapy lighting the way for medical treatments

Mar 6 2006

For the millions of people who suffer from acne, sun damage or even worse, skin cancer, there is a light of hope - photodynamic therapy or PDT.

Originally approved by the U.S. Food and Drug Administration (FDA) to treat cancer, dermatologists initially focused on using PDT to treat actinic keratoses (AKs), the earliest stages in the development of skin cancer.

As PDT treatments became refined, the therapy expanded to provide patients with a safe, non-invasive treatment option for acne, sun damage and potentially basal and squamous cell carcinomas, the two most common forms of cancer in the world.

Speaking at the 64th Annual Meeting of the American Academy of Dermatology, dermatologist Arielle N.B. Kauvar, M.D., clinical associate professor of dermatology at New York University School of Medicine in New York City, discussed how dermatologists are using PDT to successfully treat a variety of medical and cosmetic skin conditions.

"As we used photodynamic therapy to treat actinic keratoses, dermatologists discovered a variety of cosmetic benefits," said Dr. Kauvar. "Over the years, the uses of photodynamic therapy have expanded beyond the treatment of skin cancer and today it is being used to treat acne-related disorders and to help rejuvenate sun-damaged or aging skin."

PDT is a non-invasive treatment which uses a laser or light energy to activate a photosensitizer or photosensitizing agent called aminolerulinic acid (ALA). ALA is topically applied to the skin that is to be treated. Depending on the condition and severity, application time can vary from 30 minutes to several hours. A light source is then used to activate the ALA. This procedure, called topical ALA-PDT, allows specific areas of the skin to be treated while causing little or no damage to the surrounding skin and requiring minimal downtime for the patient.

The most common use for PDT in dermatology is the treatment of superficial non-melanoma skin cancer, in particular actinic keratoses (AKs). PDT appears to be the most efficient for the treatment of widespread AKs because the ALA concentrates in the abnormal cells as well as in the oil glands and hair follicles. The light source then damages or destroys the tissues that have absorbed the ALA. In some cases, AKs can be treated by a single application of ALA-PDT.

Since ALA concentrates in rapidly growing and malignant cells, ALA-PDT is being studied for the treatment of superficial basal and squamous cell carcinomas. "ALA-PDT is currently being used on superficial skin cancers on an experimental basis and results are very positive with tumors healing in one to two sessions," explained Dr. Kauvar. "Research is beginning to show that PDT may even protect against the development of squamous cell carcinomas."

As PDT research advanced, cosmetic improvements in patients with long-term sun damage was discovered. When topical ALA-PDT was used to treat large areas of sun-damaged skin, it became apparent that in addition to treating early cancerous growth, the treatment also produced cosmetic benefits. ALA-PDT helped decrease redness, reduce sun spots and freckles and it improved the overall appearance of skin including fine lines and rough skin.

"Sun damage is one of the most common conditions treated by dermatologists," said Dr. Kauvar. "Photodynamic therapy allows dermatologists to directly treat sun-damaged areas and improve cosmetic the skin's appearance without damaging surrounding skin."

More than 80 percent of Americans are affected by acne, most commonly in their teenage years. PDT targets the three main factors that cause acne: the overproduction of oil by enlarged oil glands in the skin; blockage of the hair follicles that release the oil; and a growth of bacteria called P. acnes within the hair follicles. Once applied to the skin, the ALA is absorbed in the oil glands and hair follicles. When activated by the intense light or laser, the ALA damages the oil glands and reduces the P. acnes bacteria. This treatment helps diminish, and in some cases completely remove, acne.

"Several studies have shown dramatic improvements in inflammatory acne lesions with one or more treatments," said Dr. Kauvar. "Another benefit is that it helps promote collagen formation and renewal which can help diminish acne scarring." Dr. Kauvar also noted that this advancement has alleviated the treatment time and side effects for many patients who previously relied on isotretinoin or the long-term use of antibiotics.

"Photodynamic therapy has come a long way in the treatment of various skin conditions," said Dr. Kauvar. "Topical ALA-PDT is able to effectively treat affected areas of the skin without damaging the surrounding skin and without the side effects of other treatments for precancerous growths and sun damage. It also leaves the patient with excellent cosmetic results in very little recovery time."