Efficacy evaluation and dermoscopy predictors of photodynamic therapy with different pretreatments in the treatment of actinic keratosis.

Objective: The aim of this study was to accurately evaluate the efficacy of photodynamic therapy (PDT) on actinic keratosis (AK) in the Asian population and its relationship with preconditioning and dermoscopy grading, and to determine whether some dermoscopic features of AK can independently predict the response to PDT to optimize the choice of clinical treatment.

Materials and methods: From January 2017 to January 2020, patients who were diagnosed as AK with only one lesion in our hospital were included in our study. PDT was performed after pretreatment with ablative fractional CO2 laser or cryotherapy. Logistic regression analysis was used to evaluate the characteristics of dermoscopy to determine the independent predictors of efficacy.

Results: A total of 95 patients were enrolled in the study, and the final clinical evaluation was 92 cases (96.8%) as complete remission and 3 cases (3.2%) as partial remission/no response. Dermoscopy showed complete remission in 77 cases (81.1%) and partial remission/no response in 18 cases (18.9%). No significant difference was observed in the complete remission rate of dermoscopy grade 1 lesion after laser or cryotherapy pretreatment (p > 0.05), but for dermoscopy grade 2 and grade 3 lesions, the complete remission rate (dermoscopy evaluation) of the cryotherapy pretreatment group was higher than that of laser group (p < 0.05). The probability of complete remission with red pseudonetwork at the T0 time point increased by 3.8 times (odds ratio [OR] = 3.870,95%confidence interval [CI]:1.077-13.912, p = 0.048), while the probability of complete response for lesions with slight erosion at the baseline decreased by 85% (OR = 0.150,95%CI:0.033-0.671, p = 0.013).

Conclusion: For dermoscopy grade 2 and 3 lesions, PDT after pretreatment with cryotherapy is more effective. Dermoscopy pseudo-reticular structure and microscopic erosions were independent predictors of PDT efficacy. These findings may help clinicians to better select patients with AK for PDT.