Impact of skin hydration on patterns of microthermal injury produced by fractional CO2 laser.

OBJECTIVES: The impact of skin hydration on patterns of thermal injury produced by ablative fractional lasers (AFLs) is insufficiently examined under standardized conditions. Using skin with three different hydration levels, this study assessed the effect of hydration status on microchannel dimensions generated by a fractional CO2 laser. METHODS: A hydration model (hyperhydrated-, dehydrated- and control) was established in ex vivo porcine skin, validated by changes in surface conductance and sample mass. After, samples underwent AFL exposure using a CO2 laser (10,600 nm) at two examined pulse energies (10 and 30 mJ/mb, fixed 10% density, six repetitions per group). Histological assessment of distinct microchannels (n = 60) determined three standardized endpoints in H&E sections: (1) depth of microthermal treatment zones (MTZs), (2) depth of microscopic ablation zones (MAZs), and (3) coagulation zone (CZ) thickness. As a supplemental in vivo assessment, the same laser settings were applied to hyperhydrated- (7-h occlusion) and normohydrated forearm skin (no pretreatment) of a human volunteer. Blinded measurement of MAZ depth (n = 30) was performed using noninvasive optical coherence tomography (OCT). RESULTS: Modest differences in microchannel dimensions were shown between hyperhydrated, dehydrated and control skin at both high and low pulse energy. Compared to controls, hyperhydration led to median reductions in MTZ and MAZ depth ranging from 5% to 8% (control vs. hyperhydrated at 30 mJ/mb; 848 vs. 797 µm (p < 0.003) (MAZ); 928 vs. 856 µm (p < 0.003) (MTZ)), while 14%-16% reductions were shown in dehydrated skin (control vs. dehydrated at 30 mJ/mb; MAZ: 848 vs. 727 µm (p < 0.003); MTZ: 928 vs. 782 µm (p < 0.003)). The impact of skin hydration on CZ thickness was in contrast limited. Corresponding with ex vivo findings, hyperhydration was similarly associated with lower ablative depth in vivo skin. Thus, median MAZ depth in hydrated skin was 10% and 14% lower than in control areas at 10 and 30 mJ/mb pulse energy, respectively (10 mJ: 210 vs. 180 µm (p < 0.001); 30 mJ: 335 vs. 300 µm (p < 0.001)). CONCLUSION: Skin hydration status can exert a minimal impact on patterns of microthermal injury produced by fractional CO2 lasers, although the clinical implication in the context of laser therapy requires further study.

Skin Cancer Development Is Strongly Associated with Actinic Keratosis in Solid Organ Transplant Recipients: A Danish Cohort Study.

BACKGROUND AND OBJECTIVES: Solid organ transplant recipients (SOTRs) are at increased risk of skin cancer and suffer from greater disease-specific morbidity and mortality. To risk stratify the expanding SOTR population for more targeted skin cancer screening, a detailed understanding of risk factors is needed. Using combined clinical and pathological data to capture prevalence of actinic keratosis (AK) and skin cancer, this study aimed to identify risk factors of skin cancer development in a Danish SOTR cohort. METHODS: The trial comprised a retrospective cohort study of patients attending organ transplant clinics at the dermatological departments of Bispebjerg and Gentofte Hospitals in Copenhagen, Denmark, between 2009 and 2021. In addition to pathology records, AK prevalence was determined by review of electronic medical records (EMRs) of SOTR visits which specifically included descriptions of clinical AK. Prevalence of skin cancer, here defined as basal cell carcinoma (BCC), squamous cell carcinoma (SCC) (invasive or in situ), or melanoma (invasive or in situ), was determined by EMR and pathology code review. Additional data extracted from EMRs included age, sex, Fitzpatrick skin type, transplantation date and type, and immunosuppressive therapy. The effect of risk factors on skin cancer was calculated by Cox proportional hazards regression. RESULTS: A total of 822 SOTRs were included with a mean follow-up duration of 10.8 years (SD 2.4 years). A skin dysplasia diagnosis was identified in 30% (n = 250) of the population, consisting of either AK (22%; n = 177), skin cancer (23%; n = 186) or both (14%; n = 113). An AK diagnosis predicted both SCC (odds ratio [OR]: 31.5 [95% CI: 9.8-100.6], p < 0.0001) and BCC development (OR: 2.3 [95% CI: 1.6-3.3], p < 0.0001), with AKs diagnosed an average 3.1 years before the first SCC (p < 0.0001). Correspondingly, while the risk of SCC in SOTRs without AK was 1.4% 25 years after transplantation, SOTRs with AKs had a 23% SCC risk only 10 years posttransplant. Other identified risk factors included Fitzpatrick skin type I (BCC: OR: 2.4 [95% CI: 1.2-5.0], p = 0.018; SCC: 3.2 [95% CI: 1.2-8.2], p = 0.016) and transplantation duration >15 years (BCC: OR: 1.8 [95% CI: 1.2-2.7], p = 0.007). No significant association between skin cancer development and sex or immunosuppressive regimen was shown. CONCLUSION: Keratinocyte carcinoma is strongly associated with an AK diagnosis in SOTRS and should prompt intensified skin cancer screening in affected individuals.