Oxygen saturation and perfusion changes during photodynamic therapy: use of noninvasive monitoring

Abstract

Conflicts of interest S. Ibbotson has received travel expenses from Galderma, U.K. Photodynamic therapy (PDT) requires tissue‐localized photosensitizer, light of appropriate wavelength and the presence of oxygen. Indeed, the manipulation of oxygen tension can alter the efficacy of PDT in vitro, resulting in opportunities for optimization of treatment.1 The use of topical PDT in dermatology for dysplasia and superficial nonmelanoma skin cancer is well established,2 and its routine use in clinical practice has advanced beyond our understanding of what is happening at a cellular level in human skin. While topical PDT is highly effective in selected patients, relapse rates of approximately 20% can be expected by the 5‐year follow‐up.3 In addition, current PDT regimens are not maximally effective for lesions such as thicker nodular basal cell carcinomas, and pain during irradiation can sometimes be limiting. In view of this, there is a clinical need for optimization of PDT treatment parameters, and one approach has been to maximize PDT efficiency based on in vivo data,4 such as the use of lower irradiance or pulsed‐light delivery.