Photodynamic Diagnosis of Prostate Cancer Using 5-Aminolevulinic Acid—First Clinical Experiences

Abstract

To study the feasibility of 5-aminolevulinic-acid (5-ALA)-induced photodynamic diagnosis (PDD) for the evaluation of the surgical margins (SMs) during radical prostatectomy (RP) in patients with prostate cancer (PCa). A total of 18 patients with histologically confirmed PCa (Gleason score 4 to 8, prostate-specific antigen 1 to 20 ng/mL) underwent RP. Of the 18 patients, 16 received 5-ALA (20 mg/kg) orally 2 hours before RP, and 2 served as controls without any application of 5-ALA. To study the protoporphyrin IX (PPIX) accumulation after application of 5-ALA, all harvested specimens were investigated by fluorescence microscopy and spectroscopy. In 10 of 16 patients, PDD of the SMs and the prostate was performed during RP using an incoherent light source filtered for efficient fluorescence excitation. In all 16 patients, who had received 5-ALA fluorescence microscopy showed a selective accumulation of PPIX in the PCa cells, and only weak PPIX fluorescence could be detected in benign epithelial cells and none in the adjacent stroma. The 2 patients, who had not received 5-ALA had no PPIX fluorescence in the prostate. Of 10 patients, 8 demonstrated fluorescence-negative and histologically confirmed negative margins during PDD, and 1 each demonstrated a fluorescence-positive SM that was also confirmed by histologic examination and a positive SM that was not confirmed by PPD. This is the first report of PDD for PCa using 5-ALA. These initial results have demonstrated that PPIX is selectively enhanced in malignant tissue, an essential prerequisite of PDD. Additional studies are warranted to validate these preliminary data and the efficacy of PDD for PCa during RP.