Potential Impact of Patient Vitamin D Status in AK Response to MAL-PDT

In topical photodynamic therapy (PDT) for non-melanoma skin cancers, a photosensitizing prodrug, 5-aminolaevulinic acid (ALA) or its methylated ester, methyl aminolevulinate (MAL), is converted to the endogenous photosensitizer protoporphyrinIX (PpIX). Reduced response rates are observed in thicker skin lesions, which may be due to insufficient PpIX accumulation within the target tissue. To enhance PpIX production,several physical and chemical pretreatments have been suggested. One of the chemical substances proposed to stimulate PpIX production is vitamin D because of its ability of being a keratinocyte pro-differentiating hormone. Based on in vitro and in animal model studies, we propose to study the potential impact of patient vitamin D pre-treatment in AK response to MAL-PDT.