Abstract: 【Abstract】 Objective To evaluate the association between clinical efficacy of and response to narrow-band ultraviolet B （NB-UVB） phototherapy in patients with confirmed vitiligo, and to identify factors influencing phototherapy response. Methods From January 2017 to March 2018, a total of 104 patients with vitiligo, who received NB-UVB phototherapy at the Department of Dermatology, Hangzhou Third Hospital, Zhejiang University of Traditional Chinese Medicine, were enrolled into this study. Among them, there were 55 males and 49 females, with an average age of 32.06 years （range: 4 - 64 years）. Their course of disease ranged from 2 months to 27 years, and the average course of disease was 8.15 years. The phototherapy sessions required to achieve initial repigmentation and to enter the plateau phase during which repigmentation ceased to increase with treatment sessions （plateau photothereapy sessions）, as well as effective phototherapy sessions （the difference between the phototherapy sessions required to achieve initial repigmentation and those to enter the plateau phase） were recorded. Rank sum test was used to analyze the difference in the above phototherapy sessions between patients with different response, and multiple linear regression analysis to identify factors influencing plateau photothereapy sessions and effective phototherapy sessions. Results All the 104 patients were followed up. Among them, 2 patients achieved complete repigmentation, 1 showed no response to the phototherapy, and the remaining 101 patients were enrolled into the analysis. Among the 101 patients, 52 achieved ≥ 50% repigmentation （high efficacy group）, and 49 achieved < 50% repigmentation （low efficacy group）. Compared with the low efficacy group, the high efficacy group showed significantly less phototherapy sessions required to achieve initial repigmentation （M ［P25, P75］, 8［7, 10］ vs. 10［8, 13］, Z = 3.125, P = 0.002）, but significantly more plateau phototherapy sessions （41［29, 60］ vs. 35［26, 44］, Z = -3.375, P < 0.001） and effective phototherapy sessions （32［18, 51］ vs. 24［8, 36］, Z = -4.407, P < 0.001）. Multiple linear regression analysis showed that the total number of plateau phototherapy sessions was positively correlated with vitiligo area （β = 0.360, t = 2.698, P = 0.008） and duration of disease （β = 0.215, t = 2.325, P = 0.022）, but negatively correlated with vitiligo disease activity score （VIDA）（β = -2.665, t = 3.969, P < 0.001）. Moreover, the number of effective phototherapy sessions was positively correlated with vitiligo area （β = 0.358, t = 2.582, P = 0.011） and duration of disease （β = 0.216, t = 2.276, P = 0.025）, but negatively correlated with VIDA （β = -2.669, t = -3.935, P < 0.001） and phototherapy sessions required to achieve initial repigmentation （β = -1.011, t = -4.508, P < 0.001）. Conclusions During the treatment with NB-UVB, the less the number of phototherapy sessions required to achieve initial repigmentation is, the more the number of effective phototherapy sessions is, and the better the efficacy of NB-UVB phototherapy is. Vitiligo area, duration of disease and clinical staging may provide the basis for predicting phototherapy sessions required to enter the plateau phase.

Key words: Vitiligo, Ultraviolet therapy, Treatment outcome, Response to phototherapy