Recent advances in the prevention and treatment of skin cancer using photodynamic therapy

Abstract

Photodynamic therapy (PDT) is a noninvasive procedure that involves a photosensitizing drug and its subsequent activation by light to produce reactive oxygen species that specifically destroy target cells. Recently, PDT has been widely used in treating non-melanoma skin malignancies, the most common cancer in the USA, with superior cosmetic outcomes compared with conventional therapies. The topical ‘photosensitizers’ commonly used are 5-aminolevulinic acid (ALA) and its esterified derivative methyl 5-aminolevulinate, which are precursors of the endogenous photosensitizer protoporphyrin IX. After treatment with ALA or methyl 5-aminolevulinate, protoporphyrin IX preferentially accumulates in the lesion area of various skin diseases, which allows not only PDT treatment but also fluorescence diagnosis with ALA-induced porphyrins. Susceptible lesions include various forms of non-melanoma skin cancer such as actinic keratosis, basal cell carcinoma and squamous cell carcinoma. The most recent and promising developments in PDT include the discovery of new photosensitizers, the exploitation of new drug delivery systems and the combination of other modalities, which will all contribute to increasing PDT therapeutic efficacy and improving outcome. This article summarizes the main principles of PDT and its current clinical use in the management of non-melanoma skin cancers, as well as recent developments and possible future research directions.

Keywords::

• 5-aminolevulinic acid
• ALA
• MAL
• methyl 5-aminolevulinate
• PDT
• photodynamic therapy
• photosensitizers
• skin cancer
• topical PDT

Acknowledgements

We apologize to those investigators whose work could not be directly referenced owing to space limitations. The authors are grateful to Ann Motten for her critical reading of this manuscript.

Financial & competing interests disclosure

Work in the authors’ laboratories was supported by the American Skin Association, the University of Chicago Cancer Research Center (P30 CA014599), and the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.