Using the 308 nm excimer laser, to evaluate the effectiveness of tapering the dose frequency on maintaining the clearance of psoriasis plaques after at least 75% clearance of a target plaque was achieved.
This prospective case series, conducted at a university-based dermatology practice, enrolled five adults with stable, mild-to-moderate plaque-type psoriasis vulgaris. Patients received 308 nm UVB doses to affected areas. Initial dosing was based on multiples of a pre-determined minimal erythema dose (MED). Delivered fluences were 100, 150, 200, 250, 300 and 350 mJ/cm(2), corresponding to MED levels of 1 through 6. Subsequent doses were based on response to treatment. Induction treatments were scheduled biweekly for a total of 15 treatments. After improvement of disease, tapering began as follows: one treatment per week for 4 weeks, one treatment every other week for 4 weeks, and one final treatment 4 weeks later for a total of seven treatments. The main outcome measure was maintenance of disease improvement as determined by the Psoriasis Area and Severity Index (PASI) score and percentage improvement of target lesion and total body disease during and after the laser therapy taper. A flare was defined as a 25% worsening of the percentage improvement.
All five patients completed the protocol. All patients achieved > or = 75% clearance of target plaques. No flares were noted upon completing the first month of the taper in any patient, either per percentage improvement or per PASI scores. One month after the second month of the taper (total of six treatments), no flares were noted and four out of five patients had no flares per PASI scores. No patients, either at the end of induction or at any interval during the taper, met the definition of a 50% rebound of PASI scores. Adverse effects included erythema, blisters, hyperpigmentation and erosions. All were well tolerated.
Our results reaffirm that biweekly UVB laser treatments promote clearance of psoriatic plaques. A tapering of laser treatments may be beneficial in maintaining the level of plaque clearance obtained from biweekly laser treatments. Randomized, prospective trials are needed to establish laser therapy protocols for maintaining the plaque clearance achieved with the 308 nm excimer laser.