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Actinic keratosis (AK) classification relies on clinical characteristics limited to the skin's surface. Incorporating sub‐surface evaluation may improve the link between clinical classification and the underlying pathology. We aimed to apply dynamic optical coherence tomography (D‐OCT) to characterize microvessels in AK I‐III and photodamaged (PD) skin, thereby exploring its utility in enhancing clinical and dermatoscopic AK evaluation. This explorative study assessed AK I‐III and PD on face or scalp. AK were graded according to the Olsen scheme before assessment with dermatoscopy and D‐OCT. On D‐OCT, vessel shapes, −pattern and ‐direction were qualitatively evaluated at predefined depths, while density and diameter were quantified. D‐OCT's ability to differentiate between AK grades was compared with dermatoscopy. Forty‐seven patients with AK I‐III (n = 207) and PD (n = 87) were included. Qualitative D‐OCT evaluation revealed vascular differences between AK grades and PD, particularly at a depth of 300 μm. The arrangement of vessel shapes around follicles differentiated AK II from PD (OR = 4.75, p < 0.001). Vessel patterns varied among AK grades and PD, showing structured patterns in AK I and PD, non‐specific in AK II (OR = 2.16,p = 0.03) and mottled in AK III (OR = 29.94, p < 0.001). Vessel direction changed in AK II‐III, with central vessel accentuation and radiating vessels appearing most frequently in AK III. Quantified vessel density was higher in AK I‐II than PD (p ≤ 0.025), whereas diameter remained constant. D‐OCT combined with dermatoscopy enabled precise differentiation of AK III versus AK I (AUC = 0.908) and II (AUC = 0.833). The qualitative and quantitative evaluation of vessels on D‐OCT consistently showed increased vascularization and vessel disorganization in AK lesions of higher grades. [ABSTRACT FROM AUTHOR]

Treatment-resistant actinic keratosis (AK) is of concern in clinical practice, often requiring retreatment. Microvascular assessments might help differentiate treatment-resistant from treatment-responsive AKs, enabling targeted treatment. Using dynamic optical coherence tomography, AK vascularization was investigated following daylight photodynamic therapy, comparing treatment-resistant with cleared AKs. AKs on face/scalp were graded according to the Olsen Classification Scheme and scanned with dynamic optical coherence tomography pre-treatment, and 3- and 12-months post-treatment. Employing dynamic optical coherence tomography, total vessel length, mean vessel length, mean vessel diameter, vessel area density, and branchpoint density were quantified. Thirty-eight patients with 62 AKs were enrolled, including 37 AK I, 18 AK II, and 7 AK III. Treatment-resistant AKs displayed a trend toward intensified vascularization compared with cleared AK at baseline (AKs I, II), suggested by higher total vessel length (median 144.0, IQR 104.3-186.6) and vessel area density (median 27.7, IQR 18.4-34.2) than in cleared AK (median 120.9, IQR 86.9-143.0 and median 22.9, IQR 17.3-26.8). Additionally, vascularization in treatment-resistant AK I--II appeared disorganized, with trends toward shorter mean vessel length (median 151.0, IQR 138.5-167.5) and increased branchpoint density (median 3.2, IQR 2.3-3.8) compared with cleared AK (median 160.0, IQR 152.0--169.3 and median 2.6, IQR 2.2-3.0). These findings suggest that dynamic optical coherence tomography holds potential to identify treatment-resistant AKs. [ABSTRACT FROM AUTHOR]

The efficacy of photodynamic therapy (PDT) with methyl aminolevulinate is reduced when treating actinic keratosis (AK) on the extremities in comparison with the face and scalp. Studies indicate that PDT efficacy can be improved by combining PDT with other treatment modalities. This randomized intra-individual study investigated whether pretreatment with topical 5% 5-fluorouracil (5-FU) enhanced the treatment efficacy of daylight-mediated PDT in 24 patients with AKs on the hands. One hand of each patient was given 7 days of pretreatment with 5-FU twice daily before daylight-PDT, whereas the other hand was treated with daylight-PDT alone. At 3-month follow-up the overall lesion response rate was significantly higher for the combination of 5-FU and daylight-PDT (62.7%) than for daylight-PDT alone (51.8%) (p = 0.001). Furthermore, pain and erythema in relation to treatment were similar in the 2 groups (p = 1.0 and p = 0.2, respectively). Combination therapy is a safe and effective method to improve daylight-PDT for acral AKs. [ABSTRACT FROM AUTHOR]

Multiple exposures to ultraviolet radiation (UVR) are the norm in nature and phototherapy. However, studies of the kinetics of pigmentation following UVA exposure have included only fair-skinned persons. The aim of this study was to investigate steady-state pigmentation and fading in 12 Scandinavians and 12 Indians/Pakistanis after 6 and 12 exposures on the back using broadband UVA and UVA1 with equal sub-minimal melanogenic doses (individually predetermined). Pigmentation was measured by skin reflectance at 555 and 660 nm. The UV dose to minimal pigmentation was higher in dark-skinned persons after a single broadband UVA exposure, but independent of pigmentation/skin type after single and multiple UVA1 exposures. To elicit minimal melanogenic doses after 6 and 12 exposures, every dose is lowered by a factor of 2 and 3, respectively, but the cumulative dose increases three- and four-fold, respectively. The absolute increase in pigmentation was independent of pre-exposure pigmentation; therefore the percentage increase in pigmentation was higher in fair-skinned subjects. The absolute increase in pigmentation was higher and it took 2-3 days longer to reach steady-state after 12 UV exposures compared with 6 UV exposures. Days to steady-state pigmentation and fading were independent of pre-exposure pigmentation, and fading took 5-6 months. Comparing data from a narrowband UVB source and a Solar Simulator, it was shown that pigmentation built up faster and increased more after 12 UVA exposures (16 days) than with the Solar Simulator (21 days). [ABSTRACT FROM AUTHOR]