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Clinical Updates

Sélim Aractingi, MD, PhD

Are UVB Lasers Useful for Psoriasis and Vitiligo?

Selim Aractingi

Tuesday, June 05, 2007

Patients, as well as doctors, like to imagine lasers as potentially successful and powerful. After an initial period in which lasers were used either as a destructive tool (such as to treat warts) or in a cosmetic field (such as depilation and pigmentation), it's recently been proposed that lasers be used to treat "medical conditions" such as acne, mycosis fungoides, lichen planus, lupus erythematosus, psoriasis, and vitiligo. The excimer laser consists of a 308-nm UVB coherent Xenon-chloride light excimer laser that has recently been used for psoriasis and vitiligo. Based on the first investigation with the excimer laser, a number of new phototherapeutic devices utilizing targeted phototherapy have been developed, such as 308-nm UVB lasers and lamps.

The aim of this Commentary is to discuss the results of some research on the use of excimer lasers to treat psoriasis and vitiligo, as well as to try to determine if these techniques will indeed change our daily practice.

Psoriasis

Phototherapy using either PUVA or narrowband UVB TL01 (311-nm) are widely used techniques to treat psoriasis. Apart from case reports, 15 series have been published concerning excimer laser use for psoriasis.1 To summarize these, excimer lasers are certainly very efficient in clearing psoriasis, giving 75% PASI reduction in 70% of cases2 and even up to a 90% PASI decrease in 85% of these.3

Of note, one study compared the excimer laser, a 308-nm excimer lamp, and more interestingly, TL01 UVB, in the same patients.4 The disease scores were not different in any of the treatments, suggesting similar efficacy. Overall review of these results point to three major advantages:

  1. The coherent UVB excimer is delivered through a device using an articulated arm that will target only lesional skin and spare normal skin, avoiding useless irradiation of normal skin.
  2. The delay to obtain clearing appears to be as short as 7-11 sessions with an excimer laser, with an average of 10 needed to provide clearing.5 This is to be compared historically to 25-30 sessions performed over 8 weeks for 311-nm narrowband UVB to produce clearing.
  3. The cumulative dose of UVB that has been delivered -although variable in series - appears to be lower than the cumulative dose of narrowband UVB.

In addition to these three points, some publications have also reported success using excimer lasers for difficult-to-treat lesions such as scalp psoriasis, inverse psoriasis, and even psoriasis in childhood.6,7

With these data, excimer lasers appear to be fast-acting, skin-sparing, and UV-sparing devices. So, should we shift our treatment from classical phototherapy to excimer lasers?

We should be cautious. Most studies have included a small number of cases, and others have designed the clearance of designed psoriatic plaques as the endpoint, instead of an evaluation of the patient's global disease using a PASI score. The studies have been done using protocols presenting several differences in the spot size (impact diameter) and fluences. Mainly, there is variability concerning the philosophy of the procedure, some assessing progressive increase of fluences and others performing direct delivery of the maximal fluence from the beginning. Some authors began - as with classical UVB -using a suberythemogenic dose initially followed by a stepwise increase,3,4 whereas others delivered fixed doses closer to a classical laser approach.8 These were indeed relying on the fact that lesional thick plaques will tolerate a higher dose than normal skin. Sometimes, they evaluated the minimal erythemal dose of each plaque separately.

The most important point remains the cutaneous side effects, as these were rather frequent. Erythema is reported in up to 81% of cases, and blisters are found in 63% of some series with hyperpigmentation developing in 50-75% of cases.1,3 Pain was typical. Some authors report these effects much more frequently with the laser than with classical UVB phototherapy, as a consequence of delivering intense fluence to the plaques. Some authors and/or investigators have speculated on the fact that the delivery of high energy in a short period of time with erythema and/or blisters is similar to the accumulation of solar burns, known to be the main risk factor for melanoma. There is at least a theoretical higher risk of skin carcinogenesis.

The long-term carcinogenic risk of NB UVB phototherapy is unclear.9 Therefore, long-term carcinogenesis studies remain to be evaluated with UVB light sources.

Finally, one advantage of the technique - a device that spares normal skin - is also a limit for patients who have a large area of involvement: Those who have more than 20% of total body area affected by psoriasis cannot practically be treated with this technique. In localized psoriatic plaques, the excimer laser is an interesting tool. However, there is no comparative study of high-potency steroids with excimer lasers in these situations.

Vitiligo

What has been said about the advantage of excimer laser for sparing non-lesional skin is much more important concerning vitiligo treatment. Indeed, one of the usual problems in vitiligo patients treated with classical phototherapy is the increase in the contrast that results from irradiation of normal skin surrounding white plaques.

Excimer lasers focusing on plaques avoid this side effect, which is poorly accepted by many patients. Studies targeting vitiligo are still sparse - only 10 series have been published. A 57% partial repigmentation of plaques after 4 weeks and 9% of complete repigmentation was shown by Spencer et al.,10 whereas 85% of partial repigmentation and 20% of complete repigmentation was demonstrated by Passeron T et al.11 In this last paper, when excimer lasers were associated with tacrolimus, the response was better.

Also interesting is the fact that lesions that were in non-exposed areas did not respond to the procedure, indicating lack of systemic effect from laser phototherapy. Of note, other later studies did not show efficacy of tacrolimus alone in vitiligo.11 Baltas et al. reported 4 out of 6 patients showing 50-95% repigmentation.12 The best results of excimer lasers are obtained after 12 weeks of treatment, apparently best if 3 weekly sessions are delivered.13 Reported side effects mainly include erythema, with blistering being more rare than in psoriasis. The highest rate appears to be 20%.11 This is explained by the fact that fluences were lower than those used in psoriasis.

Although laser excimer appears to be very promising in nearly all these studies, one has to keep in mind that these were small series with a non-blinded evaluation of the results. However, in vitiligo, alternative therapies are scarce and therefore excimer lasers appear to represent an interesting and promising strategy. It is probable that we will use this procedure more frequently in vitiligo management.

Conclusions

Excimer lasers offer a new way to improve delivery of UVB. They can be useful in treating limited psoriasis plaques. Risk for long-term carcinogenesis for the excimer laser must be evaluated as for other UVB phototherapies. In contrast, it appears to be a much more rational therapy for vitiligo.

References

  1. Passeron T, Ortonne JP. Use of the 308-nm excimer laser for psoriasis and vitiligo. Clin Dermatol. 2006;24(1):33-42.
  2. Trehan M, Taylor CR. Medium-dose 308-nm excimer laser for treatment of psoriasis. J Am Acad Dermatol. 2002;47(5):701-8.
  3. Gerber W, Arheilger B, Ha TA, et al. Ultraviolet B 308-nm excimer laser treatment of psoriasis: a new phototherapeutic approach. Br J Dermatol. 2003;149(6):1250-8.
  4. Kollner K, Wimmershoff MB, Hintz C, et al. Comparison of the 308-nm excimer laser and a 308-nm excimer lamp with 311-nm narrowband ultraviolet B in the treatment of psoriasis. Br J Dermatol. 2005;152(4):750-4.
  5. Feldman SR, Mellen BG, Housman TS, et al. Efficacy of the 308-nm excimer laser for treatment of psoriasis: results of a multicenter study. J Am Acad Dermatol. 2002;46(6):900-6.
  6. Gupta SN, Taylor CR. 308-nm excimer laser for the treatment of scalp psoriasis. Arch Dermatol. 2004;140(5):518-20.
  7. Pahlajani N, Katz BJ, Lozano AM, et al. Comparison of the efficacy and safety of the 308 nm excimer laser for the treatment of localized psoriasis in adults and in children: a pilot study. Pediatr Dermatol. 2005;22(2):161-5.
  8. Asawanonda P, Anderson RR, Chang Y, et al. 308-nm excimer laser for the treatment of psoriasis: a dose-response study. Arch Dermatol. 2000;136(5):619-24.
  9. Ibbotson SH, Bilsland D, Cox NH, et al. An update and guidance on narrowband ultraviolet B phototherapy: a British Photodermatology Group workshop report. Br J Dermatol. 2004;151(2):283-97.
  10. Spencer JM, Nossa R, Ajmeri J. Treatment of vitiligo with the 308-nm excimer laser: a pilot study. J Am Acad Dermatol. 2002;46(5):727-31.
  11. Passeron T, Ostovari N, Zakaria W, et al. Topical tacrolimus and the 308-nm excimer laser: a synergistic combination for the treatment of vitiligo. Arch Dermatol. 2004;140(9):1065-9.
  12. Baltas E, Nagy P, Bonis B, et al. Repigmentation of localized vitiligo with the xenon chloride laser. Br J Dermatol. 2001;144(6):1266-7.
  13. Hofer A, Hassan AS, Legat FJ, et al. Optimal weekly frequency of 308-nm excimer laser treatment in vitiligo patients. Br J Dermatol. 2005;152(5):981-5.
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