Journal of Dermatology 2009; 36: 579–582
doi: 10.1111/j.1346-8138.2009.00710.x
ORIGINAL ARTICLE
Efficacy of 308-nm excimer light for Japanese patients
with psoriasis
Yusuke NIWA, Toshio HASEGAWA, Subin KO, Yasuhiro OKUYAMA,
Akiko OHTSUKI, Atsushi TAKAGI, Shigaku IKEDA
Department of Dermatology, Juntendo University School of Medicine, Tokyo, Japan
ABSTRACT
Ultraviolet irradiation therapy, including psoralen and ultraviolet A therapy and narrow-band ultraviolet B (310–
312 nm) therapy, is a widely used and highly efficient treatment modality for psoriasis. Therapy with 308-nm excimer
light has been reported to be effective for the treatment of psoriasis vulgaris. To evaluate the efficacy of 308-nm
excimer light therapy for Japanese psoriasis patients, seven patients (six men and one woman) with plaque-type
psoriasis were treated with 308-nm excimer light at 7–14-day intervals. The Psoriasis Severity Index (PSI) was calculated for individual plaques in order to assess the effectiveness of the therapy. A 74.9% mean improvement in
the PSI was observed after 10 treatment sessions. These results suggested that targeted irradiation with 308-nm
excimer light leads to rapid and selective improvement in plaque-type psoriatic lesions without unnecessary
radiation exposure to the surrounding unaffected skin.
Key words:
excimer light, psoriasis, target irradiation.
INTRODUCTION
Psoriasis is a chronic inflammatory skin disease that
affects approximately 1–3% of the population in the
USA and Europe.1 In contrast, the prevalence of this
disease in Japan is very low (0.025%).2 Various
phototherapeutic strategies, including psoralen and
ultraviolet A (PUVA) therapy and narrow-band ultraviolet B (NB-UVB: 310–12 nm) therapy, have been
widely used and shown to be highly effective in the
treatment of psoriasis.3–5 However, large areas of
unaffected skin around the lesions are also irradiated
when these conventional phototherapies are used.
Three hundred and eight nanometer excimer light
is a novel source of radiation that offers the advantage of selective target irradiation without unnecessary exposure of unaffected skin. Therapy with
308-nm excimer light has been reported to be effective in the treatment of psoriasis vulgaris.6,7 However,
the efficacy and safety of this treatment modality
in Japanese psoriasis patients remains unknown.
Therefore, we examined the efficacy of this modality
for the treatment of Japanese psoriasis patients.
METHODS
A total of seven patients (six men and one woman)
with localized severe chronic plaque-type psoriasis
vulgaris were recruited in the study (Table 1). The
exclusion criteria included a history of skin cancer or
that of photosensitivity disorders. In addition, patients
who had received systemic therapy and ⁄ or phototherapy within 8 weeks prior to the study were not
recruited. Informed consent was obtained from each
of the subjects prior to therapy initiation. The age of
the patients was 26–64 years (average age, 54.3),
and their skin type was Japanese skin type (JST)
I or II. The therapies previously administrated to
Correspondence: Yusuke Niwa, M.D., Ph.D., Department of Dermatology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku,
Tokyo 113-8421, Japan. Email: [email protected]
Received 9 October 2008; accepted 11 August 2009.
2009 Japanese Dermatological Association
579
Y. Niwa et al.
Case no. ⁄ sex ⁄
age ⁄ JST
1 ⁄ M ⁄ 58 ⁄ II
2 ⁄ M ⁄ 60 ⁄ II
3 ⁄ M ⁄ 47 ⁄ I
4 ⁄ M ⁄ 62 ⁄ II
5 ⁄ M ⁄ 64 ⁄ II
6 ⁄ M ⁄ 63 ⁄ II
7 ⁄ F ⁄ 26 ⁄ II
Mean (SD)
Site of
treated
plaque
Initial dose
(mJ ⁄ cm2)
PSI
(before)
PSI
(after)
PSI
improvement
(%)
Lower leg
Scalp
Back
Lower leg
Scalp
Scalp
Lower leg
300
200
200
200
300
200
200
8
7
7
7
9
6
8
7.4 (1.0)
2
2
2
2
2
1
2
1.9 (0.4)
75
71
71
71
78
83
75
74.9 (4.5)
Table 1. Patient characteristics and evaluation of treatment outcomes
JST, Japanese skin type; PSI, Psoriasis Severity Index.
them included treatment with topical corticosteroids
(n = 7), topical calcipotriol (n = 5), PUVA (n = 1),
NB-UVB (n = 3) and systemic retinoids (n = 3).
The VTRAC Excimer Lamp System (PhotoMedex,
Montgomeryville, PA, USA) with a wavelength of
308 ± 2 nm, irradiance of 150 mW ⁄ cm2 and spot
size of 18.9 cm2 (6.1 cm · 3.1 cm) was used. Psoriatic lesions that failed to show satisfactory
response to any of the previously employed antipsoriatic treatments were selected. The treatment
was administrated at 7–14-day intervals: the initial
ultraviolet (UV) radiation dose used was determined
according to the JST (Table 2), and the dose was
increased by 50 mJ ⁄ cm2 at each session unless
side-effects were observed. No additional anti-psoriatic treatments were allowed during the treatment
courses. Prior to each session, clinical evaluation
was performed for individual plaques using the
Psoriasis Severity Index (PSI). The PSI was calculated by summing the scores of 0–4 (0, none; 1,
mild; 2, significant; 3, moderate; 4, severe) assigned
for erythema, induration and scaling; the maximum
possible score was 12. Response to treatment was
evaluated on the basis of improvement in the PSI
evaluated as follows: 1 – (PSI [after treatment] ⁄ PSI
[before treatment]).
Table 2. Initial ultraviolet radiation dose
JST
Initial UV dose (mJ ⁄ cm2)
I
II
III
100–200
200–300
300–400
JST, Japanese skin type; UV, ultraviolet.
580
RESULTS
The irradiated sites were the scalp (n = 3), lower leg
(n = 3) and back (n = 1). The average PSI before
the treatment was 7.4 (6–9); however, this score
decreased to 1.9 (1–2) after 10 sessions of treatment.
The mean reduction in the PSI score was 5.6 (5–7).
The mean PSI improvement was 74.9% (71–83%). Of
the seven patients, four showed 75% improvement
(Table 1).
Case 1 was a 58-year-old man. He presented with
a localized severe chronic psoriatic lesion on the right
lower leg that showed resistance to treatment with
topical corticosteroids, topical calcipotriol and PUVA
(Fig. 1a). He was successfully treated with 308-nm
excimer light (Fig. 1b,c). The PSI decreased from 8 to
2 after 10 treatment sessions.
Case 2 was a 60-year-old man. He presented with
severe localized chronic psoriatic lesions on the scalp
that showed resistance to treatment with topical corticosteroids (Fig. 2a). He was successfully treated
in the same manner in which case 1 was treated
(Fig. 2b). The PSI decreased from 7 to 2 after 10 treatment sessions.
No serious adverse effects were observed.
Square-shaped erythematous lesions corresponding
to radiation spots were observed during the treatment
course in cases 1, 3, 4 and 7, including a few blisters
noted in cases 1 and 3; however, these lesions were
resolved within a week or so. Moreover, occasionally,
irradiated areas were observed to undergo hyperpigmentation in cases 1, 3, 4 and 7; however, the
hyperpigmentation was observed to disappear naturally. No side-effects were observed in the patients
with scalp psoriasis.
2009 Japanese Dermatological Association
308-nm excimer light for psoriasis
(a)
(b)
(c)
Figure 1. Clinical presentation of case 1 (a) before, (b) after five treatment sessions and (c) after 10 treatment sessions.
DISCUSSION
(a)
(b)
Figure 2. Clinical presentation of case 2 (a) before and
(b) after 10 treatment sessions.
2009 Japanese Dermatological Association
Three hundred and eight nanometer excimer light
is a xenon chloride (XeCl) UV-B light, which is a
recently developed, incoherent but narrow-band light
source.6,7 It has been reported to be effective in the
treatment of psoriasis.8–11 The intensity of this light is
much higher than that of NB-UVB light; consequently,
fewer treatment sessions are required for the clearance of the psoriatic plaques when using these lights
than in conventional phototherapy. This light can be
used for directly and precisely irradiating the localized
skin lesions, sparing the surrounding apparently
unaffected skin from unnecessary radiation exposure;
this minimizes the risks of side-effects such as photoaging and possible development of cutaneous malignancies. It was previously reported that the superior
efficacy of excimer laser in the treatment of psoriasis is attributable to the higher induction of T-cell
apoptosis in the psoriatic lesions as compared to
that observed with NB-UVB therapy.12,13 Although
308-nm excimer light is simpler and cheaper compared to laser systems, it has an efficacy that is
similar to that of laser irradiation, because it delivers
the precise wavelength and intensity of light as that
required in lasers. In addition, a 308-nm excimer light
with a spot size of 6.1 cm · 3.1 cm is superior to
lasers for the treatment of large skin lesions.
It was shown that 84% of the psoriasis patients,
who were treated twice weekly beginning with three
581
Y. Niwa et al.
minimal erythema dose (MED), showed a 75%
improvement or higher after 10 or fewer 308-nm excimer laser treatments.10 Further, it was reported that
the mean PSI score could be reduced from 8.6 during
pretreatment to 2.13 after 10 weeks of 308-nm lamp
treatment administered three times weekly beginning
with 1 MED.6 Goldinger et al. demonstrated that the
mean reduction in Psoriasis Area and Severity Index
(PASI) score was 5.5 after 12 treatments three times
weekly using 200 mJ ⁄ cm2 as the initial UV dose that
was increased by 100 mJ ⁄ cm2 at each session.11 In
contrast, we performed the treatments at 7–14-day
intervals beginning with initial doses of almost 0.5–1
MED for each JST group, as reported previously.14
Our results showed 74.9% PSI improvement; the
mean reduction in PSI score was 5.6 after 10 treatment sessions. The efficacy of the 308-nm excimer
lamp, as confirmed in our study, was either equal to
or a little less than that reported in previous studies,
even though the initial doses were correlated with a
low fluence; in addition, the frequency of therapy was
low compared to that reported in previous studies.
In the present study, we demonstrated the targeted
radiation of plaque-type psoriatic lesions with
308-nm excimer light to produce rapid and selective
improvement in lesions without unnecessary radiation
exposure to surrounding unaffected skin. Our results
suggested that 308-nm excimer light is an alternative
therapeutic option for the treatment of localized psoriasis resistant to conventional treatments even in the
Japanese population. Further studies are necessary
to determine the standard protocol for the treatment
of psoriasis vulgaris patients using 308-nm excimer
light, which offers greater positive effects and lower
adverse effects to Japanese psoriasis patients.
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2009 Japanese Dermatological Association