Targeting psoriatic plaques with a single, high dose of UVB yields favorable outcomes

St. Louis - Turbo UVB phototherapy with the 308 nm excimer laser performed using a single high dose appears to be a well-tolerated and rapidly effective method for treating chronic plaque psoriasis, according to the results of an open-label pilot trial undertaken by dermatologists at Case Western Reserve University, Cleveland.

Speaking at the annual meeting of the Society for Investigative Dermatology, Mark Kagen, M.D., reported outcomes for a series of 15 patients enrolled in the study. The participants had skin types II-VI and had their lesions treated at a single session using an individualized dose equivalent to 10 times the predetermined minimal erythema dose. The mean dose administered was 2000 mJ.

During follow-up that continued over eight weeks, most patients experienced onset of clearing within one or two weeks and a maximum response by week four that was maintained in most cases throughout the study period. By week eight, mean PASI score had improved from 19 to 8.

"While UVB phototherapy with the excimer laser is usually administered in a three times a week regimen of incrementally increasing doses over a period of weeks to months, we initiated this study based on our hypothesis that psoriatic plaques could tolerate a higher dose of UVB light than normal skin. Our experience is with a small number of patients, but the results were impressive with respect to the onset, degree and durability of the responses in some patients," Dr. Kagen says.

"If this is corroborated with further investigation, use of this new approach would offer potentially important benefits for minimizing cumulative UVB exposure and greatly enhancing patient convenience for receiving this treatment modality."

Dr. Kagen performed the study as a dermatology resident at Case Western Reserve University Hospitals. Kevin Cooper, M.D., professor and chairman of dermatology, was the principal investigator. Since August, Dr. Kagen has been in private practice in Orlando, Fla.

The study

The patients entered into the study all had psoriasis vulgaris-type lesions. Only plaques on the trunk or extremities were treated. Lesions located on the face, scalp, folds and mucosal surfaces were excluded.

Dr. Kagen tells Dermatology Times that a potential safety advantage for reducing carcinogenicity risk using the single, high dose regimen is hypothetical. While its use would likely reduce cumulative UVB exposure, it is not known how the risk of cancer might be affected by intermittent, intense irradiation.

"Available evidence so far suggests no increase in cases of skin cancer in patients treated with excimer laser phototherapy, but longer follow-up in greater numbers of patients is needed," Dr. Kagen says.

As part of the study protocol, serial biopsies were obtained to evaluate the potential mechanism underlying the efficacy of the targeted UVB treatment. Results from fluorescent antibody staining to evaluate caspase activity revealed that like other forms of UVB phototherapy, the excimer laser treatment was associated with T-cell apoptosis in the epidermis and dermis.

"We found there was quite a dramatic increase in T-cell apoptosis soon after treatment was performed, and, to our knowledge, we are the first to demonstrate this response occurs with targeted UVB phototherapy using the excimer laser," Dr. Kagen says.