ABSTRACT
Protoporphyrin IX (PPIX)-based photodynamic therapy (PDT), following the instillation of 5-aminolaevulinic Acid (5-ALA) or in particular its ester derivative Hexylester Aminolevulinate (HAL), is an interesting approach in this context (Krieg et al., 2000; Jichlinski and Leisinger, 2001). e reason for this is that HAL is approved, reimbursed, and clinically used in many western countries to detect early bladder cancers (Wagnières et al., 2014) and leads to a selective production of PPIX in early NMIBC, thus preventing photodamage to deeper tissue layers of the bladder wall. In addition, the instillation time is signicantly shorter with HAL than with 5-ALA. e broad absorption spectrum of PPIX, with peaks in the range of 390-660 nm, allows the use of various excitation wavelengths presenting dierent penetrations depths into the bladder wall, such as blue, green, or red alone, or a combination of those such as white-light illumination. erefore, dierent clinical research protocols have been launched in dierent countries (Kriegmair et al., 1996; Waidelich et al., 2001; Shackley et al., 2002; Bader et al., 2013).
