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Psoriasis
light in the treatment of four stable psoriatic plaques.
7
The primary plaques in the same patient with varying levels of thickness were
purpose of this study was to determine a dose–response relationship treated with different doses of UVB light, with decreased dosages
when using excimer laser. The fluences used in treating each plaque administered to thinner plaques. In this group, 83.7% of patients
were based on multiples of MED. The MED was determined based on achieved complete clearance. Compared with the original group, this
non-psoriatic skin, defined specifically as the minimal fluence of light subset required fewer treatments in order to achieve clearance (seven
that produced barely perceptible erythema after 24 hours. Based on versus 13 treatments) and a lower cumulative UVB dose (6.25 versus
this, fluences were categorised as low (0.5 and one multiple of MED), 11.25J/cm
2
). This concept of MED-I is important because, in the
medium (two, three, four and six multiples of MED) and high (eight and traditional history of phototherapy, MED was determined using
16 multiples of MED). When examined after four weeks of twice-weekly uninvolved, non-psoriatic skin. This study demonstrated the benefit of
treatment, those sites receiving high fluences showed better tailoring therapy to individual lesions, taking into account psoriatic
improvement compared with sites receiving low or medium fluences. plaque thickness and the tolerance of that particular psoriatic lesion.
Following the 10-week treatment period, all plaques treated with high This individualised protocol was justified by the variation in psoriatic
fluences demonstrated complete clearance. Furthermore, when lesions even within the same individual.
patients were examined four months following treatment, all sites
treated with fewer than eight MED multiples showed recurrence. Excimer laser therapy has also demonstrated efficacy in the treatment
However, psoriatic sites that received only a single irradiation with high- of palmoplantar psoriasis, a challenging clinical condition that can cause
fluence treatment (eight or 16 multiples of MED) were still in remission. difficulty with daily functioning for affected individuals.
11
In a study of 54
Thus, high fluences of UVB, up to 16 multiples of MED, can induce a patients with palmoplantar psoriasis, patients were treated with the
prolonged remission of psoriatic disease after clearing with only a monochromatic excimer laser for 10 sessions every seven to 10 days.
single excimer laser treatment. This may be beneficial for patients with UVB dosage was determined based on patient skin type and adjusted
localised psoriatic disease. An important observation made by the based on clinical response. Following four months of therapy, complete
authors was that those lesions with more scaling tended to respond remission was demonstrated in over half of the subjects (57%) and
less favourably to targeted UVB light. This is not surprising, as it is partial remission in 24% of patients. Following two months of treatment,
known that a thickened stratum corneum layer can obstruct light 44 of 54 patients (81%) achieved at least a 75% improvement in their
penetration. Overall, this study demonstrated that a single high-fluence palmoplantar psoriasis. Generally, faster clinical response was observed
treatment or repeated treatments with moderate fluences of light from in palmar lesions compared with sole lesions. Overall, the benefit
the 308nm laser can result in significant clearing of plaque psoriasis. achieved was maintained at the four-month follow-up visit for the vast
majority of patients. This study demonstrated the value of excimer laser
In a multicentre study by Feldman et al., the efficacy of the 308nm therapy in treating palmoplantar psoriasis. Laser therapy can also be
excimer laser was evaluated in 80 patients with limited plaque psoriasis utilised in the treatment of scalp psoriasis.
12
Scalp psoriasis frequently
(less than 10% body surface area [BSA] affected).
8
Patients were treated represents a treatment challenge, as UV phototherapy may not
twice weekly for 10 treatment sessions, i.e. five weeks of therapy total. adequately reach the scalp due to hair covering the psoriatic lesions. In
Of these patients, 72% achieved at least 75% clearance of the target a retrospective study, 35 patients with scalp psoriasis who failed
plaque. Furthermore, approximately half of patients achieved 90% intensive topical therapy were treated with excimer laser twice weekly.
clearance with fewer than 10 treatments. Common side effects Manual separation of the hair was used during treatment, and dosages
included erythema, blistering and hyper-pigmentation. This multicentre were determined according to skin type. Results demonstrated that 49%
study demonstrated that targeted laser therapy can achieve clearance of patients achieved >95% clearance, and another 45% of patients
of target plaques in fewer than 10 patient visits, and is generally a well- achieved between 50 and 95% clearance of their scalp psoriasis. In
tolerated treatment. Another single-centre study by Trehan et al. addition, the high output of targeted UVB light makes rapid treatments
showed that patients achieved ≥95% clearance in their psoriatic possible, with full scalp treatment requiring less than 15 minutes.
plaques after an average of 10.6 excimer laser treatments. Additionally, Adverse effects included erythema and blistering, most commonly
remission time was 3.5 months following this eight-week treatment occurring around the ears and nape of the neck. Such adverse effects
course.
9
Another clinical trial evaluated the efficacy of excimer laser in occurred in all patients with an average of four episodes per patient, but
120 patients with <20% body surface area affected by plaque psoriasis. rapid recovery was achieved with symptomatic treatment.
Patients were initially treated twice weekly for three weeks, followed by
weekly treatments until clearance was achieved.
10
UVB dosage was Regarding its clinical efficacy, authors have proposed that the XeCl laser
administered at three times the pre-determined MED, which was based may be more efficacious because it is more effective in inducing T-cell
on uninvolved skin. Of the 102 patients who completed treatment, apoptosis compared with conventional NB-UVB.
13
As psoriasis is
nearly two-thirds (65.7%) achieved greater than 90% clearance of their mediated by activated T lymphocytes infiltrating the epidermis, the
psoriatic lesions after 10 or fewer treatments. cytotoxic effect of high-intensity UVB light on inflammatory cells is an
important mechanism underlying its therapeutic efficacy. In a study
Interestingly, a subset of 40 patients were treated using a protocol comparing NB-UVB light with 308nm XeCl laser, both forms of UVB light
based on the MED of involved skin (MED-I). This second protocol was induced T-cell apoptosis, but the XeCl laser induced apoptosis to a
developed because the reaction of psoriatic plaques to UVB irradiation greater extent at each energy density tested.
depends on the thickness of the plaque, rather than the MED of non-
involved skin. MED-I was determined using psoriatic skin, using the Previously, excimer laser therapy was considered an efficacious
lowest dosage producing perceptible erythema without blistering of the treatment for mild to moderate psoriasis, and was frequently used in
psoriatic plaque. MED-I measurements were carried out in addition to patients with ≤10% BSA affected. However, the authors have
calculating epidermal thickness of the plaques. A correlation was made experienced effective use in patients with up to 20% BSA (see Figure 1).
between starter dose and epidermal thickness; therefore, different The XTRAC
®
Ultra (PhotoMedex, Montgomeryville, PA) has an average
12 EUROPEAN DERMATOLOGY
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