Efficacy and Safety of Liquid Nitrogen Cryotherapy for Lichen Simplex Chronicus: A Meta-Analysis

Lichen simplex chronicus (LSC) is characterized by localized lichenification and intense itching. It has been reported that the added use of liquid nitrogen cryotherapy (LNC) for LSC has significant efficacy and notable safety. Therefore, we conducted a meta-analysis based on existing randomized controlled trials (RCTs).We searched RCTs on LNC for LSC published up to August 2020 using various databases, including PubMed, EMBASE, Web of Science, Cochrane Central Register of Controlled Trials, China Network Knowledge Infrastructure (CNKI), Chinese Biomedicine (CBM), Chinese Scientific Journals Database (VIP), and WanFang Database. Other studies were manually identified using the references cited in reviews. We applied fixed- or random-effects models, and all analyses were performed using Review Manager 5.4 software.Twelve RCTs involving 1,066 participants provided eligible data for the meta-analysis. Based on the clinical effective rate, LNC treatment of LSC (risk ratio, RR 1.25, p = 0.005, I2 = 82%) was superior to controls. Subgroup analysis showed that the use of LNC alone (RR 1.04, I2 = 95%, p > 0.05) is not more effective than other therapies in the treatment of LSC, but the addition of LNC to the existing treatment increases the total clinical efficacy. Furthermore, the combined effect of LNC and topical medication (RR 1.39, I2 = 0%, p < 0.0001) was better than that of LNC and oral medication (RR 1.30, I2 = 0%, p < 0.00001). Greater frequency of LNC treatment did not improve the efficacy (thrice a week: RR 1.39 [1.21, 1.60]; twice a week: RR 1.27; once every 2 weeks: RR 1.32). Data from 6 RCTs with 508 participants showed no significant difference in AEs (p = 0.31) associated with added LNC treatment.The addition of LNC (applying a cotton swab soaked with liquid nitrogen to wipe the lesion for approximately 10 s each time) to topical ointments, is effective and safe in the treatment of LSC. Increasing the treatment frequency of LNC did not necessarily improve the efficacy.