Clinical and genetic predictors of response to narrowband ultraviolet B for the treatment of chronic plaque psoriasis

Abstract

There is considerable variability in the number of exposures of narrowband ultraviolet B (NB-UVB) needed to clear psoriasis and in the duration of remission. We assessed clinical parameters as predictors of the number of exposures needed to clear psoriasis and of the duration of remission. The influence of genetic polymorphisms of the vitamin D receptor (VDR) on treatment response was also evaluated. This was a prospective study of 119 patients with chronic plaque psoriasis treated with NB-UVB until clearance was achieved. They were then followed for up to 1 year or until relapse occurred. The frequency of the Fok1, Apa1, Bsm1, Taq1 and rs4516035 polymorphisms of the VDR gene was assessed in 93 of the 119 patients. Of the 119 patients, 105 completed the course of phototherapy. Using an intention to treat analysis, 83% of the initial cohort (99 of 119 patients) achieved clearance, in a median of 26 exposures (interquartile range 19-35) with a median remission duration of 16 weeks (interquartile range 9-22). Factors significantly associated with a lower number of exposures to clearance included a lower baseline Psoriasis Area and Severity Index (P = 0·004), lower baseline Dermatology Life Quality Index (P = 0·047), female sex (P = 0·043), lower body weight (P = 0·008), and a higher number of previous courses of TL-01 (P = 0·005). The only clinical factor influencing remission duration was number of exposures (P = 0·0009), with a decreased remission duration in those who required a greater number of exposures to clear. The Taq1 VDR polymorphism (rs731236) also significantly predicted remission duration (P = 0·038). Patients homozygous for the C allele, which is associated with decreased activity of the VDR, had a shorter remission duration than those heterozygous for the allele (P = 0·026) and those homozygous for the T allele (P = 0·013). This study highlights the fact that both genetic and clinical parameters are important in determining treatment outcomes in psoriasis.