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

Background: 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.

Objectives: 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.

Methods: 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.

Results: 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).

Conclusions: This study highlights the fact that both genetic and clinical parameters are important in determining treatment outcomes in psoriasis.