Interstitial photodynamic therapy for prostate cancer: a developing modality

Patients with early stage prostate cancer are generally treated with either a radical prostatectomy or radiotherapy. While both approaches have good survival outcomes, they are associated with significant side effects and non-trivial failure rates. Photodynamic therapy has been studied as a possible treatment for both recurrent and primary prostate cancer. Interstitial photodynamic therapy requires strict dosimetry, mandating an understanding of photosensitizer concentration, tissue oxygenation, and light fluence. Preclinical studies have investigated the optical characteristics of prostate tissue showing variability both prior to and during photodynamic therapy. Canine studies have been undertaken demonstrating necrosis of the glandular epithelium to depths ranging from 1 to 17mm from a single light source depending on the photosensitizer used. Necrosis is typically followed by glandular atrophy with maintenance of the gross prostatic architecture. Urinary complications in the canine studies were more prominent when transurethral light was used and often occurred in a dose-dependent fashion. Few clinical trials have been undertaken to date investigating photodynamic therapy of the prostate in patients. The limited data that are available suggest that photodynamic therapy is tolerable in patients with recurrent and primary disease. This review summarizes the preclinical and clinical work in photodynamic therapy in the prostate and suggests areas of future research which must be addressed before the technique can become a practical option for patients.