SAN DIEGO – Although previous studies of 1,064-nm Nd:YAG lasers for the treatment of onychomycosis have reported significant mycological cure rates, results from a newer, ongoing study challenge such findings.
At the annual meeting of the American Academy of Dermatology, Dr. Boni E. Elewski reported findings from a trial in which she and her colleagues set out to answer two questions: Can fungal organisms be killed by heat at temperatures tolerable to patients? And, can a laser be directly fungicidal on a growing fungal colony or dilute suspension?
Dr. Boni E. Elewski
Dr. Elewski and her colleagues conducted a heat kill study of three fungi: Trichophyton rubrum, Epidermophyton floccosum, and Scytalidium.
For T. rubrum, they found that growth was halted after the nail was treated at 50° C for 15 minutes. For E. floccosum, they found that growth was halted after the nail was treated at 50° C for 10 minutes, and for Scytalidium, growth was halted after the nail was treated at 55° C for 5 minutes. "However, nail temperatures that reach 40-41° C cause enough pain for patients to pull away, and the maximum nail temperature patients could tolerate was 45° C," said Dr. Elewski, professor of dermatology at the University of Alabama at Birmingham.
In part two of the study, the researchers used a 1,064-nm Nd:YAG laser to treat colonies and dilute solutions before growth occurred. They used various laser parameters, including spot sizes ranging from 3 to 5 mm, pulse durations that ranged from 100 to 300 milliseconds, fluences of 15 to 50 J/cm2, and frequencies of 2 to 10 Hz. "We found that there was no effect on fungal growth at numerous settings, and the temperature of the agar plate reached about 40° C," Dr. Elewski said. "We decided to take this knowledge and move it into our clinical practice."
In an ongoing study that has enrolled 10 patients to date, she and her associates use a 1,064-nm Nd:YAG laser for a protocol that involves five treatments at settings of 16 J/cm2, 0.3 microseconds, and 2 Hz. They use a 5-mm spot size with more than 300 pulses over the nail in a predetermined pattern. "You see some clearance," Dr. Elewski said of the results so far. "We have no mycological cures to date, but improvement as shown by other companies is noted. Some improvement may be seen, but in my opinion a durable response is needed to satisfy patients."
In a 2010 study from Yugoslavia, mycological cures were reported using a fluence of 35-40 J/cm2, Dr. Elewski said, "but our patients could not tolerate anything above 16 J/cm2, at least without a digital block. All I can assume is that patients in Yugoslavia are significantly heartier than patients in Alabama" (J. Laser and Health Academy 2010;1:1-8).
She concluded her remarks by noting that photodynamic therapy "may be an option for your patients who have failed other treatments or who could not tolerate another treatment. Laser treatment is still under investigation, but might be desirable for those who would be satisfied with an improvement."
Dr. Elewski disclosed that Cutera provided research funds for the study. She said that she had no financial conflicts of interest to disclose, and emphasized that she has never been a paid consultant to any laser device company.