In search for optimal schedule during long term treatment of port wine birthmarks - data from single center retrospective cohort study with a small prospective extension.

Treatment of Port-wine birthmarks (PWB) requires multiple laser sessions. This study aims to determine the optimal long-term approach for PWB treatment using a 532 nm large spot laser. A retrospective analysis was conducted on fifty-five Caucasian patients, aged 6 to 59, who underwent total number of 412 sessions with interval between sessions varied from 16 to1867 days with 3D imaging assessed changes in lesion area and color before and after treatment. The median maximal improvement (GCEmax) achieved during the series of laser treatments was 63.61%. The first two laser procedures had a median maximal improvement of 31.19%, while the first 5,10,15 and 20 laser procedures had 49.84%, 58.01%, 60.13%, and 60.17%, respectively. Patients who stopped treatment for more than 180 days exhibited a worsening of the GCEmax that gradually increased over time reaching 34,7% for the brakes longer than 270 days. Additional laser sessions reversed this decline. Our findings suggest that the effectiveness of treating port wine birthmarks with large spot 532 nm laser plateaus on average after nine laser sessions. Untreated birthmarks tend to worsen over time loosing up to the third of the initial effect and worsening is evident 6 months from the last treatment. In order to avoid it, maintenance treatment should be encouraged after reaching plateau.