Indole 3-acetic acid-photodynamic therapy in the treatment of multiple actinic keratoses: A proof of concept pilot study.

Background: Actinic Keratoses (AK) are considered a form of in situ Squamous Cell Carcinoma (SCC) arising on chronically photoexposed skin. PDT with ALA or MAL is an effective treatment for multiple AK due its high Overall Response Ratio (ORR) but is burdened by important drawbacks: time-consumption, pain and high costs. Indole-3 acetic acid (IAA) is a newly described photosensitizer with proven clinical efficacy on seborrheic dermatitis and acne vulgaris. The aim of the study was to assess efficacy, safety and tolerability of a cycle of IAA-PDT at 0.015% in liposomal gel in the treatment of multiple AK of face or scalp.

Methods: We treated 12 patients affected by multiple AK on face/scalp with 4 weekly applications. The product was applied for 15min under occlusion; medicated area was then irradiated for 15min with a LED light at 520nm wavelength for a total fluency of 9J/cm2.

Results: No grade 3/4 SAE have been reported; all 12 patients successfully completed the cycle. CR at 3 months follow-up was 25%, with an ORR of 50%. Patients reported almost no pain during irradiations, with mean overall Visual Analogic Scale (VAS) score of 0.3±0.7. IAA-PDT led to a significant improve on Disease Life Quality Index (DLQI) mean score, but no variations on Actinic Keratosis Quality of Life (AKQoL) mean score.

Conclusions: Although larger studies are needed, this is a first "proof of concept" of IAA- PDT as a possible treatment for multiple AK on face/scalp.