Theodore Rosen, MD, said of laser therapy for onychomycosis: ‘The literature is scant.'

Are non peer-reviewed sources spot-on in their conclusion that laser therapy is highly effective for onychomycosis? Not so much. Theodore Rosen, MD, professor of dermatology, Baylor College of Medicine, Houston, explained why during his presentation of "Laser Therapy of Onychomycosis" at Friday's Hot Topics session.

"The literature is scant," he said. "A lot of it is posted on the websites of doctors' offices. Maybe the doctor has written a white paper, but that paper never appears in press in peer-reviewed literature."

Food and Drug Administration approval of laser therapy for onychomycosis does not equate to proven efficacy, but only safety, he noted. Furthermore, the FDA only says laser therapy provides "temporary improvement in nail appearance" or "temporary increase in clear nails."

Dr. Rosen did share a series of peer-reviewed journal articles, laser company websites, and practitioner white papers that showed images of alleged improvement or clearing. After one, he said, "I will leave it to your discretion whether post-therapy represents a cured patient. It is an improved patient."

Dr. Rosen also pointed out the inconsistency of results; no one conclusion or result held up from one study or report to another. "Images from various studies show everything from total clearance to questionable benefit," he said.

Laser therapy emerges at a time when onychomycosis is clearly a diagnosis and treatment dilemma.

"Onychomycosis is a vexing problem to treat effectively and safely, and we are looking for something that is reliable," Dr. Rosen said "We aren't even sure the best way to make a diagnosis. There is obviously an autosomal-dominant predisposition to the disease, and fungi are everywhere, so even if you treat  there is likely to be some probability of recurrence. We know that topical therapies are not terribly effective, and we know systemic therapy, while it may work, has potential side effects, so that's why we keep looking for new modalities."

He acknowledged advantages with laser therapy, "if it worked." Lasers can deliver therapy directly to diseased tissue. They do not come with the risks of drug interactions, adverse events, or cumulative toxicity.

In terms of how lasers are supposed to work, theory points to two proposed mechanisms of action. One is that laser therapy is ablative, with the generation of heat sufficient to kill fungi preferentially without ill effect on tissue. Another action involves photoinactivation, the generation of reactive oxygen species via light interaction with cytochrome complex and cellular membranes (plasma and mitochondrial).

"Is laser therapy the future of onychomycosis therapy?" Dr. Rosen asked rhetorically. "I would love it if it were. I believe it is a promising modality, but the paucity of data and long-term follow-up make it almost impossible to decide. The jury is still out, so stay tuned."