Interstitial photodynamic therapy of the canine prostate using intra-arterial administration of photosensitizer and computerized pulsed light delivery

Purpose: We determined the feasibility of complete treatment of the canine prostate and long-term effectiveness of interstitial photodynamic therapy using the intra-arterial photosensitizer QLT0074 (benzoporphyrin derivative 1,3-diene C,D-diethylene glycol ester A ring) (QLT, Vancouver, British Columbia, Canada) administration and pulsed light delivery. Materials and Methods: The prostate gland of 11 dogs were infused with QLT0074 via the prostatovesical arteries (2 mg drug per artery bilaterally) under fluoroscopic guidance. Immediately following infusion the prostate was surgically exposed and 7 optical fibers with 1.5 cm cylindrical diffusers in after loading sheaths were inserted into the prostate through a template. Light was delivered sequentially to the optic fibers via a computer driven switch system. One dog was sacrificed 6 days after photodynamic therapy to assess acute tissue effects. The other 10 dogs were monitored for clinical tolerance and urinary function, and sacrificed at between 3 and 11 months. Prostate specimens were examined microscopically to evaluate long-term tissue reactions. Results: Comprehensive destruction of the prostate was noted in the acute dog. Except for urinary retention and mild hematuria no other perioperative complications were observed in the chronic dogs. Urodynamic examination did not reveal deleterious bladder and urethral function. Average prostate volume decreased 71% at 3 months and 56% after 6 months (p = 0.007 and 0.014, respectively). Microscopic evaluation revealed prostate glandular epithelial atrophy, stromal fibrosis and mononuclear cell infiltration. Conclusions: Interstitial photodynamic therapy using intra-arterial QLT0074 and pulsed light delivery is safe and feasible for comprehensive destruction of the canine prostate. Clinical trials are required to confirm it for managing prostate diseases.