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The 308-nm Excimer Laser Is Practical Therapy for Psoriasis

Because it can be aimed precisely at individual plaques, this laser is effective and spares surrounding skin.

We know from action spectrum studies that longer-wavelength UVB is the most effective waveband for the treatment of psoriasis. Narrowband UVB (TL-01, 311 nm) is a proven therapy for generalized psoriasis, but what treatment is suitable for resistant lower-leg lesions or solitary plaques unresponsive to focal therapies? Could the 308-nm laser, which can be aimed precisely at individual plaques, be safe and effective while sparing surrounding skin?

Investigators with extensive experience with the xenon-chloride gas 308-nm excimer laser studied its efficacy for treating plaque psoriasis in 20 volunteers. The average PASI score of studied lesions was 7.5, indicating moderate activity, although some plaques were of a thick, chronic type. In each patient, 6 plaques were treated 3 times weekly for up to 8 weeks, and a 7th plaque served as an untreated control. Doses were increased to the next highest allowable dose provided there was no adverse response to the previous dose. In the 15 subjects who completed the study, the mean number of treatments needed to achieve clearance -- defined as >95% reduction in PASI score -- was 10.6; the mean cumulative dose was 6.1 J/cm²; and the average remission time was 3.5 months. Administration was painless, although 7 of 15 patients experienced 1 or 2 episodes of focal blistering (1.0 to 1.5 cm in diameter), which healed within 2 weeks without scarring. Control plaques showed no PASI score change.

Comment: In both theory and practice, this treatment is effective: The excimer 308-nm laser produced response and remission times similar to those achieved with narrowband UVB phototherapy, but the excimer laser effected faster clearance at a lower cumulative dose and spared unaffected skin from unnecessary exposure. The blistering response may raise a problem for patients. Controlled trials comparing the adverse effects associated with narrowband phototherapy and laser treatment, as well as mouse photocarcinogenic data, are needed. I suspect that until such information is available, this expensive, high-tech treatment will remain confined to specialist centers.

— James Ferguson, MD, FRCP

Published in Journal Watch Dermatology January 14, 2003

Citation(s):

Trehan M and Taylor CR. Medium-dose 308-nm excimer laser for the treatment of psoriasis. J Am Acad Dermatol 2002 Nov; 47:701-8.

• Medline abstract (Free)