Photodynamic therapy for actinic keratosis: a trend towards a decrease in irradiance without loss of efficacy for a better tolerability

Anne-Sophie Vignion-Dewalle (1) , Claire Vicentini (2, 1) , Grégory Baert (1) , Elise Thecua (1) , Fabienne Lecomte (1) , Laurent Mortier (1, 2) , Serge Mordon (3, 4, 1)

1 ONCO-THAI - Thérapies Laser Assistées par l'Image pour l'Oncologie - U 1189
2 Département de Dermatologie [CHRU Lille]
3 INSERM - Institut National de la Santé et de la Recherche Médicale
4 Faculté de Médecine Henri Warembourg - Université de Lille

Photodynamic therapy (PDT) is an established treatment for actinic keratosis (AK). The conventional approved PDT protocol in Europe (C-PDT) involves red-light photoactivation at irradiances higher than 60 mW/cm 2 , making the treatment painful. Several clinical studies have reported similar efficacy and better tolerability when using red-light photoactivation at lower irradiances. The aim of the study was to investigate whether there is a minimum irradiance threshold for red-light photoactivation above which there is no further improvement in efficacy. A photodiode sensor connected to a power meter was used to measure the irradiance delivered to 114 AKs on the scalp and forehead of 19 patients during C-PDT using the Aktilite CL 128 (Galderma SA, Switzerland). The widely ranging measured irradiances, resulting from the heterogeneous photoactivation over the treatment area provided by the Aktilite CL 128, were cross-referenced with the clinically evaluated complete responses (CR) at 3 months. The 66 AKs in CR at 3 months received an average irradiance of 30.9 mW/cm 2 (standard deviation: 16.7 mW/cm 2) compared to 33.3 mW/cm 2 (standard deviation: 17.9 mW/cm 2) for the 48 AKs in incomplete response. No significant effect of the irradiance on the CR at 3 months was found (odds ratio for a 6 mW/cm 2-unit change, 0.96; 95% confidence interval, 0.83 to 1.10; p=0.53). No minimum irradiance threshold could therefore be determined in the considered irradiance range. A red-light device enabling homogeneous irradiation at a lower irradiance than the Aktilite CL 128 may therefore provide similar efficacy and higher treatment tolerability than C-PDT.

Mots clés: Photodynamic therapy; actinic keratosis; Aktilite CL128; irradiance; complete response

Domaines: Sciences du Vivant [q-bio]; Cancer; Ingénierie biomédicale; Dermatologie

Anne-Sophie Vignion-Dewalle, Claire Vicentini, Grégory Baert, Elise Thecua, Fabienne Lecomte, et al.. Photodynamic therapy for actinic keratosis: a trend towards a decrease in irradiance without loss of efficacy for a better tolerability. 17th International Photodynamic Association World Congress, Jun 2019, Cambridge, Massachusetts, United States. ⟨hal-02870081⟩