Repeated exposure to fractional CO(2) laser delays squamous cell carcinoma formation and prevents clinical and subclinical photodamage visualized by line‐field confocal optical coherence tomography and histology

OBJECTIVES: Ablative fractional laser (AFL) is a well‐established modality for treating ultraviolet radiation (UVR)‐induced skin photodamage. We aimed to investigate the potential of AFL to delay squamous cell carcinoma (SCC) formation and prevent photodamage in a preclinical UVR‐induced SCC model. MATERIALS AND METHODS: Hairless C3.Cg‐Hr ( hr )/TifBomTac mice (n = 50) were exposed to UVR three times weekly throughout the study. UV‐exposed mice were randomized to two groups that received dorsal CO(2) AFL (10 mJ/mb, 10% density) or no treatment. AFL was performed every other week for a total of 16 weeks (nine treatments in total). The primary outcome was time to tumor occurrence. In a subset of mice on Day 150, prevention of clinical photodamage was assessed by examination of skin tightness and dyspigmentation. Concomitantly, assessment of subclinical photoprevention based on normalization of keratinocyte dysplasia, dermo‐fiber morphology (collagen and elastin fibers), and skin thickness, was performed using line‐field confocal optical coherence tomography (LC‐OCT) and histology. RESULTS: Repeated AFL treatments delayed SCC tumor development compared to UVR control mice by 12, 19, and 30 days for first, second, and third tumors, respectively (p ≤ 0.0017). Compared to UVR controls, AFL prevented photodamage both clinically and subclinically, based on LC‐OCT and histology. In the epidermal layer, AFL imparted photopreventative effects including reduced dyspigmentation and keratinocyte dysplasia (1 vs. 2.5, p = 0.0079) and partial normalization of the epidermal thickness (p < 0.0001). In the dermis, AFL led to twofold greater skin tightness (p = 0.0079), improved dermo‐fiber structure, and dermal thickness (p = 0.0011). CONCLUSION: In conclusion, repeated AFL treatments of UVR‐exposed skin significantly delayed SCC tumor formation and prevented clinical and imaging‐assessed subclinical signs of photodamage, indicating a potential for AFL in prevention strategies for SCC and photodamage in high‐risk populations.