Photodynamic therapy with fractional ablation tackles actinic keratoses

February 1, 2011

The use of fractional ablation and photodynamic therapy (PDT) effectively treats precancerous lesions and is well-tolerated by many patients, according to an associate professor and chief of division of dermatologic and cosmetic surgery at Mount Sinai Medical Center in New York.

Key Points

New York - The use of fractional ablation and photodynamic therapy (PDT) effectively treats precancerous lesions and is well-tolerated by many patients, according to an associate professor and chief of division of dermatologic and cosmetic surgery at Mount Sinai Medical Center in New York.

"I use it (PDT) for everything from sun damage and evidence of precancers and large areas," says Ellen Marmur, M.D., who opts for the erbium:YAG laser.

PDT, either enhanced or standard, gives a superior cosmetic result to many other methods of treating actinic keratoses (AKs), such as the use of liquid nitrogen, so patients are very loyal to PDT as a treatment, according to Dr. Marmur.

Other treatment options have drawbacks. The downside to liquid nitrogen is that it leaves white spots. Topical treatments take about a month to six weeks to eliminate AKs; thus, patients' adherence to therapy is required. For a patient population that increasingly wants immediate results and no downtime, six weeks is too long. "Many of my patients in Manhattan want the therapy done quickly," Dr. Marmur says.

In most patients, Dr. Marmur applies microdermabrasion to remove the dead stratum corneum. PDT is then used to deliver 5-aminolevulinic acid (ALA) into the mitochondria of precancerous cells.

"The engines of these cells are running faster, and they are able to absorb things faster," Dr. Marmur says. "There is preferential absorption by cancerous or precancerous cells, converting from ALA to an endogenous molecule called protoporphyrin 9 (Pp9)."

Plan of attack

In a subset of patients, Dr. Marmur says she takes a more aggressive approach, using fractionated laser followed by PDT. "If people are able to tolerate it (PDT) well, but they still have sun damage, I would use more aggressive treatment and use a fractionated laser first," Dr. Marmur says.

The fractionated laser drills thousands of microscopic pinholes into the skin, allowing for optimal penetration of ALA, Dr. Marmur says.

"You get wonderful drug delivery," she says. "There is saturation into the empty pinholes, and the medicine can get down into the skin. You are physically removing pieces of precancer, and you are also delivering the medication further than the epidermis, which is where we thought the precancers originate. New research suggests the dermis plays a role in cancerogenesis. This is the best way to be proactive about precancers becoming SCCs (squamous cell carcinoma) and BCCs (basal cell carcinoma), which are possibly lethal."

The side effect profile of standard PDT is a burning sensation following treatment, redness and photosensitivity for two days. The side-effect profile of fractionated laser therapy plus PDT is more intense.

Not for everyone

Dr. Marmur says patients whose skin is easily irritated by something like a mosquito bite may not be good candidates for fractionated ablation plus PDT.

"I offer standard treatment for patients who are very sensitive," Dr. Marmur says. She says those who demonstrate a tolerance to regular PDT and enhanced PDT and are very motivated are good candidates for fractionated laser therapy.

For patients who are receiving fractionated ablation plus PDT, the frequency is usually between one and three sessions annually, with a reduction in the frequency of treatments in patients in the second year of treatment. A broad range of patients can undergo fractionated ablation and PDT, Dr. Marmur says. "I have done this in patients age 30 to patients who are in their 80s," she says.

Microdermabrasion plus PDT does not pose a risk of scarring, because the medicine is only released into the epidermis. Theoretically, there is an elevated risk of scarring with the use of fractionated ablation plus PDT because the medicine is hitting the dermis.

"I have seen no cases (of scarring), but I have selected my patients such that they have tolerated PDT well," Dr. Marmur says. "There is a broad range of tolerance to PDT."

Disclosures: Dr. Marmur is an adviser to DUSA Pharmaceuticals.