Phototherapy in dermatology: recent advances

Vancouver, British Columbia - One of the interesting developments in the use of lasers for hair removal is paradoxical hypertrichosis, or hair regrowth, which has been observed in some patients, notes Dr. Harvey Lui, professor and chairman in the division of dermatology at the University of British Columbia.

Speaking here at the 57^th Annual Meeting of the Pacific Dermatology Association, Dr. Lui discussed recent advances using phototherapy in dermatology, the theory behind why photodynamic therapy is effective, and how it is beneficial because it selectively targets tissues.

Reporting results

"It has been observed that the hair appears to grow back more than prior to the start of the laser sessions," Dr. Lui tells Dermatology Times. "There isn't a definitive explanation for why that is happening. It may be the localized trauma of the laser that is synchronizing hair growth. The hair that does grow back grows back in lockstep fashion."

Narrowband ultraviolet B (NB-UVB) has shown greater efficacy than broadband ultraviolet B treatment, and it can be used for several conditions such as vitiligo, atopic eczema or psoriasis. It can eliminate the need for psoralen and long-wave ultraviolet radiation A (PUVA), the use of which has diminished, in part, due to its potential carcinogenic effect. PUVA was estimated to be seven times more carcinogenic than UVB in a recent study published by Stern and colleagues.

Impetus

The impetus behind developing NB-UVB was studies in treating psoriasis that found that longer-wavelength UVB was more efficacious than shorter UVB wavelengths to clear the condition.

Whenever possible, dermatologists should review a patient's treatment records before initiating phototherapy, especially if a patient reports no effect or light "sensitivity" from a previous course of phototherapy, Dr. Lui says. They should warn their patients who receive phototherapy that they might develop mild sunburn, depending on their sensitivity to light. Treatment is best initiated by exposing a limited area at a time if light sensitivity is suspected. If, during maintenance treatments, the patient repeatedly burns without there being an increase in dose or increase in frequency of treatments, it's best to reduce the light dose by 20 percent to 40 percent.

A study that Dr. Lui published with other researchers in the Archives of Dermatology in June 2004 investigated the possibility of using a clinical tool to measure treatment response to vitiligo. Patients who had stable vitiligo involving 5 percent of their total body surface distributed in a symmetrical way were administered NB-UVB phototherapy three times a week to half of the body for either 60 treatments or six months. The contralateral side, which received no treatments, acted as the control.

Researchers used the Vitiligo Area Scoring Index (VASI), to measure the difference in repigmentation from baseline compared to repigmentation of the patches over time.

The extent of repigmentation was 42.9 percent on the treated side compared to 3.3 percent on the untreated side after six months, a difference that was statistically significant. In addition, there was a significant difference between control and NB-UVB groups after two months of therapy. The study's authors concluded that legs, trunk and arms were the parts of the body more likely to repigment and found that hands, even when exposed to significantly higher doses of NB-UVB, did not repigment.

Combination therapy

Increasingly, clinicians may use biologic agents in addition to phototherapy to maximize results in their patients, notes Dr. Lui, and to reduce the overall number of treatments.

Lasers and light sources are being widely used, and not necessarily by trained clinicians, but implementing regulations to curb or reverse the trend of non-physicians using the technologies would now be difficult, according to Dr. Lui.