Utilization of phototherapy and treatment response in adults with psoriasis: Data from the Malaysian Psoriasis Registry

Dear Editor, Psoriasis is a chronic, relapsing skin disease, which is associated with comorbidities and economic burden. Treating psoriasis with phototherapy in South East Asia requires special considerations with regard to different dosing regimens and side effect profiles due to different skin types.1,2 To our knowledge, there is no large population study or patient registries assessing the treatment outcome of phototherapy in psoriasis especially for patients with skin of color. Malaysia is composed of different ethnicities with different skin phototypes. The Malaysian Psoriasis Registry (MPR) is a prospective cohort study with an ongoing collection of data of psoriasis patients in Malaysia. Analysis of the MPR data from July 2007 to December 2019 was performed with the aim to describe the utilization of phototherapy and treatment outcomes in adults with psoriasis. Of 20,898 adult psoriasis patients who were notified to the MPR, 547 patients (2.6%) underwent phototherapy within the last 6 months of MPR notification. The sociodemographic and clinical characteristics of the study population are demonstrated in Table 1. Comparisons were made between the cohort who received phototherapy and those who had not. There was a significantly higher proportion of males in the phototherapy cohort compared with those who did not receive phototherapy (63.6% vs. 56.0%). The phototherapy cohort group had more severe psoriasis with a significantly higher proportion of face and neck, scalp and nail involvement, a higher body mass index (BMI), as well as a higher rate of systemic therapy usage in the past 6 months compared with the nonphototherapy group. Fortynine percent of the phototherapy cohort had a BSA involvement of >10% compared with 21.2% in the nonphototherapy cohort, and more patients in the phototherapytreated group had poorer quality of life (QoL) compared with the nonphototherapy group (DLQI >10: 46.6% vs 37.3%). The majority of patients (86.9%) had NBUVB. Preand posttreatment responses were analyzed after at least 3 months of phototherapy and based on serial followup data within 12 months. Meaningful clinical response is defined as improvement by at least 1 scale based on BSA (4 categories of severity based on BSA i.e. <5%, 5– 10%, >10– 90%, >90%) and/or DLQI improvement by at least 1 point, with no changes in topical therapy and systemic medication. There were 96 patients who had complete data for the assessment of treatment outcomes. Different outcomes were observed based on physicians' and patients' assessments in which BSA improvement was documented in 23 patients (40.4%) while DLQI improvement was documented in 53 patients (57.6%). DLQI improvement was documented in 11 patients (20.7%) despite static BSA involvement while 3 patients (5.7%) with worsening BSA showed improvement in DLQI. On the other hand, 7 patients (13.2%) experienced worsening of DLQI despite improvement in BSA, and another 3 patients (5.7%) experienced worsening of both DLQI and BSA involvement. Figure 1 shows comparison of QoL preand postphototherapy according to the DLQI domains. There was significant improvement in the domains of “symptoms and feeling” and “leisure.” Overall, approximately twothirds (66.7%) of our phototherapy cohort achieved meaningful clinical response. A higher mean baseline DLQI was the only significant predictive factor for meaningful clinical response (12.8 ± 7.2 vs. 7.7 ± 5.3, p = .001). In our cohort, phototherapy is underutilized as only 2.6% of patients had phototherapy even though onefifth (21.2%) had a BSA involvement of >10%. This could be due to a lack of favorability among treating dermatologists and patient factors such as logistics and time off work. A higher willingness to attend regular phototherapy among the males is postulated for the observation of male preponderance in the phototherapy cohort. NBUVB remains the type of phototherapy of choice as it is as effective as PUVA, with fewer side effects.3 BSA improvement was noted in 23 patients (40.4%). Among our phototherapy cohort, 39.1% were active smokers and 67.7% were obese. These are among the factors associated with poor response to phototherapy.4 We were unable to compare our findings with other published data, which used PASI as a treatment endpoint. Our treatment response was based on improvement in BSA. The improvement in DLQI postphototherapy was consistent with previous studies.5 It is interesting to know that some patients demonstrated improvement in their DLQI scores despite a status quo in BSA involvement. The different outcomes observed based on physicians' and patients' assessments can be explained by the improvement in symptoms as shown in Figure 1, thus enabling more social activities (leisure). Besides, the degree of improvement in terms of thickness, erythema, and scaliness was not captured with BSA assessment. On the contrary, a few patients reported worsening of DLQI despite improvement of BSA. This concurred with Arora et al. where they concluded that clinical severity and quality of life improvement are independent of each other.6 One possible explanation for this is