Retrospective Analysis of the Therapeutic Outcomes of Microneedle Radiofrequency on Melasma by Optical Coherence Tomography: A Observational Pilot Study

Background: No preferred treatments for melasma are known, owing to its underlying complicated pathomechanisms; microneedle radiofrequency (MRF) has recently been used to treat melasma. Objectives: We aimed to investigate the effects and pathomechanisms of melasma treated by MRF and identify the possible determining factors for good response. Methods: Therapeutic outcomes were measured using the Melasma Area and Severity Index (MASI) and artificial intelligence-assisted optical coherence tomography (OCT) evaluation for collagen and pigmentation at baseline and 2 months after each treatment. Participants were divided into good- (≥25% reduction in MASI) and poor-response (<25% reduction in MASI) groups after the last MRF treatment. Results: Two patients achieved fair response and three patients achieved poor response. Overall OCT analysis showed that the confetti/granular melanin ratios (melanin aggregation index) decreased, the distance between melanosomes increased, and the size of melanin decreased. The number of dendritic cells (DCs) decreased. In subgroup analysis, the continuity of the basement membrane was improved in the fair-response group, and the melanin aggregation index and the number of DCs were decreased in the poor-response group. A higher baseline confetti/granular melanin ratio trended towards poorer therapeutic response. Conclusions: This pilot study used OCT to assess the therapeutic efficacy of MRF for melasma and identify the characteristics of individuals for whom MRF is effective. The statistical results were exploratory and descriptive. Further large-scale, randomized controlled studies are required to prove the efficacy of MRF in treating melasma and the feasibility of OCT in investigating the treatment response of melasma.