Preliminary study of transurethral photodynamic therapy mediated with Tookad in a canine prostate model

摘要

Background: photodynamic therapy (PDT) mediated with vascular acting photosensitizer Tookad (pd-bacteriopheophorbide) was investigated as an alternative modality for treating prostate cancer. Our previous studies show that Tookad PDT can induce marked prostatic tissue lesion but minimal urethral lesion. In this study a transurethral procedure was used to evaluate the response of the prostatic urethra to direct urethral irradiation. Materials and Methods: Tookad solution (2.5 mg/ml) was administered (1 mg/kg) through IV catheter by an infusion pump over 10 min. A diffuser fiber (1 cm active length) was inserted into the prostatic urethra. The light irradiation (50 or 100 J/cm) started at 4 min after the onset of drug infusion. Urinalysis was performed for 24 - 48 h post PDT. One week after PDT, prostates (n = 4) were removed at necropsy and subjected to histopathological examination. Results: The cross section of prostates showed severe hemorrhagic and necrotic lesions on the right lobe. The diameter of the lesion, measured from urethra to capsule, was >13 mm for 50 J/cm treatment and > 18 mm for 100 J/cm, respectively. Although underlying periurethral lesion was visible, the urethral surface was intact and prostatic urethra was open. Conclusions: The joint point of the diffuser tip and the guide fiber might be bent while passing through the sharp turn at the Ischial Arch, which could affect the light distribution and cause the asymmetric lesion. Nonetheless, the transurethral direct irradiation can induce marked prostatic tissue lesion but minimal urethral lesion.