In vivoconfocal microscopy efficacy assessment of daylight photodynamic therapy in actinic keratosis patients

Reflectance confocal microscopy (RCM) is a noninvasive diagnostic technique with an acceptable sensitivity and specificity for actinic keratosis (AK). We evaluated efficacy of daylight photodynamic therapy (DL‐PDT) in patients with AK using a new RCM atypia scoring system. All patients with AK lesions (Grade I–II) were included in our study (2012–15). Baseline clinical, dermoscopy and RCM evaluations were followed by DL‐PDT. In the first follow‐up, clinical examination, dermoscopy and RCM imaging of the treated area were carried out. Atypia scoring and cell size measurements were used to compare before and after RCM images. From 40 lesions (20 patients with mean age of 75·5 years), complete resolution and partial response of the actinic damage was detected in 80% and 17·5% of lesions, respectively. No cellular atypia was seen in the follow‐up RCM images of 57·5% of lesions (n = 23), while in 40% of lesions (n = 16) minimal changes to the honeycomb pattern of the epidermis were seen in the follow‐up RCM images (atypia score 1). Only one lesion showed minimal or no clinical response, and a persistent moderate amount of atypia in RCM. Furthermore, atypia score and mean cell size decreased significantly in the follow‐up DL‐PDT RCM images (P < 0·001, P = 0·001, respectively). RCM features of actinic damage at cellular level have been shown to correlate well with the results of a clinical assessment of AK lesions. This study confirms that in vivo RCM technology might be an additional technique to monitor the efficacy of DL‐PDT for AK.