OBJECTIVE: To investigate the efficacy of the cyclic on-off treatment compared to the conventional continuous excimer laser treatment.

DESIGN: A randomized, controlled, split-body, non-inferiority study. SETTING: The trial was performed in two tertiary health care centers in Korea.

PARTICIPANT: Twelve patients (16 pairs of lesions) with stable symmetric vitiligo less than 5 years' disease duration were enrolled.

INTERVENSION: The paired symmetric vitiliginous lesions were randomized to either the continuous or the cyclic on-off treatment. All lesions were treated twice weekly for 9-month: continuously, or cyclically with 2-month treatment and 1-month intermission (total 3 cycles). Topical tacrolimus was applied throughout the trial.

OUTCOME MEASURES: The repigmentation was assessed using an image analysis program with clinical photographs. The primary outcome was mean difference of repigmentation rates and the non-inferiority margin was set at 10%. During intermission period, the clinical changes such as loss of repigmentation or worsening of the vitiligo lesions were assessed.

[Study design and population] A randomized, controlled, split-body, non-inferiority trial was designed.

After obtaining informed consent, 12 patients with stable symmetric vitiligo less than 5 years' disease duration were enrolled.

The patients taking systemic steroids or having enlarging lesions were excluded. The paired symmetric vitiliginous lesions were randomized to either the continuous or the cyclic excimer laser treatment.

Total duration of study was 9 months.

In cyclic excimer laser treatment, the cycle was arbitrarily determined that one cycle consists of a 2-month treatment period (on) and a consecutive 1-month intermission period (off) (total 3 cycles during the trial).

[Treatment protocol]

The lesions were treated twice a week. Initial irradiation dose was 50 mJ/cm2 on face and 100 mJ/cm2 on trunk and extremities. If there had not been minimal asymptomatic erythema, energy level was escalated by 50 mJ/cm2. In cyclic treatment, the treatment resumed after intermission with the previously used irradiation dose.

Topical tacrolimus 0.1% ointment was applied in both twice daily throughout whole length of the trial.

[Assessment and primary outcome] Photographic documentation of lesions was conducted every month and the degree of repigmentation was assessed with a repigmentation rate (%) from the baseline by using an image analysis program (Digital Researcher for Vitiligo Area Evaluation, Dr. VAE, Korea).

An intention-to-treat analysis was planned, and last observation carried forward method was applied to impute the missing value in the presence of dropouts.

The primary outcome was mean difference of quantitative changes in repigmented area between continuous and cyclic on-off treatment. The non-inferiority margin was set at 10%. During intermission period in the cyclic treatment, the clinical changes such as loss of repigmentation or worsening of the vitiligo lesions were assessed.

[Statistical analysis] All statistical analyses were conducted using R 3.2.4 (R Foundation for Statistical Computing, Austria) and a P value <0.05 was considered statistically significant.

Inclusion Criteria:

• Patients with symmetric vitiligo
• Patients with less than 5 years' disease duration

Exclusion Criteria:

• The patients taking systemic steroids
• The patients with currently enlarging lesions
• The patients who cannot follow the treatment schedule