ALA/PDT is classic marriage of convenience

July 1, 2006

Blue light has proven to be significantly more compatible with ALA than other partners, such as intense pulsed light and or pulsed dye lasers.

Albuquerque - Over the last five to 10 years, the development of a new modality - aminolevulenic acid (ALA) in combination with photodynamic therapy (PDT) - has advanced the frontline in the battle against actinic keratosis (AK).

According to Eduardo Tschen, M.D., "This combination treatment is important because not all patients respond well to chemical peels or liquid nitrogen - one person may be sensitive to certain chemicals and another to cold temperatures. Dermatologists need options so they can tailor treatment to individuals."

ALA with PDT is even more important, he adds, when you consider a broader context: a worldwide epidemic of AK and a growing body of evidence that suggests these lesions are not just pre-cancerous but small cancers.

Considering whys and wherefores

To remove crusty AK lesions, dermatologists prescribe creams that induce a chemical peel over a period of several weeks or burn them off in the office either with liquid nitrogen or ALA/PDT.

One indication for ALA/PDT is the number of lesions on a patient.

"It's okay to spray one or two or five lesions with liquid nitrogen," Dr. Tschen says, "but if you have 100, it's much easier to treat with light."

One way or another, dermatologists must induce inflammation in order to destroy AK lesions, so a second indication for ALA/PDT is the patient's tolerance for redness and swelling. Those with many lesions have the option of using a product like Efudex (5-Fluorouracil 5 percent and Imiquimod 5 percent, Valeant Pharmaceuticals International) but their inflammation may persist for four weeks or longer compared to one week to two weeks for PDT.

In general, Dr. Tschen says, "I prefer to use photodynamic therapy if a person has more than 10 lesions or if the lesions are on the scalp, ears, face or hands."

It's contraindicated for patients with porphyria, an inherited sensitivity to light, or for those taking medications that render them temporarily sensitive to light. Patients with Alzheimer's and Parkinson's are often unable to hold still for light therapy. Treatment of lesions located on the eyelid is contraindicated because ALA is difficult to apply there and light could damage the eye.

Reviewing treatment modality efficacy

Over the short term, Dr. Tschen says, there isn't any significant difference in the efficacy of one modality over another.

But, he emphasizes, "If you follow patients for one to two years, and there aren't any studies that have, I think you might see some differences favoring ALA/PDT."

He posits that because both self-treatment with a cream and burning with liquid nitrogen have an arbitrary element, patients may or may not follow directions. One dermatologist may spray lesions for five seconds to 20 seconds while another may treat according to a different time frame to which he or she subscribes.

Protocols for ALA/PDT therapy

The use of ALA/PDT, however, is more standardized. Pre-treatment with ALA takes place in the office on the afternoon prior to photodynamic therapy.

The time interval between ALA and PDT should be at least 12 hours. Sun exposure must be avoided.

For PDT, Dr. Tschen says, it's critical to use a light source matched to ALA.

"It has to be a marriage - the wavelength must fit the chemical."

And blue light has proven to be significantly more compatible with ALA than other partners, such as intense pulsed light and or pulsed dye lasers.