title: Interstitial photodynamic therapy in the canine prostate.
abstract: OBJECTIVE
  To determine the depth of tissue destruction and the minimum light dose required for necrosis in interstitial photodynamic therapy (PDT), as a prerequisite for the investigational therapy of patients.
  
  
  METHODS
  Seven adult beagle dogs were given 2 mg/kg of the photosensitizer Photofrin intravenously and two controls received none. After 24 h, 450 J/cm of 630 nm wavelength laser light was delivered interstitially to the prostate via a 2 cm long diffuser fibre. Seven single-fibre treatments were performed in five sensitized dogs and two single-fibre treatments in the controls. The two remaining sensitized dogs had two fibres placed 10 mm apart within the prostate to determine the coalescence of PDT lesions. The penetration depth of light was measured in all prostates, and after PDT the extent of necrosis was assessed histologically.
  
  
  RESULTS
  The mean (standard deviation, SD) radius of PDT destruction around each diffuser was 5.3 (1.4) mm and PDT lesions overlapped in prostates treated with two fibres placed 10 mm apart. There was no observable tissue damage in the controls. The mean (SD) minimum light dose required for PDT necrosis was 84 (64) J/cm2. Differences among animals in the light penetration depth were small, with a mean of 2.14 (0.2) mm, and did not correlate with the depth of necrosis (P = 0.07). Bleeding around the optical diffuser fibre impeded light penetration.
  
  
  CONCLUSIONS
  Interstitial PDT in the canine prostate using Photofrin produced modest volumes of tissue necrosis. The minimum light dose required to induce necrosis was variable because bleeding was unpredictable in relation to the optical fibre.
authors.affiliation: CRC Department of Experimental Radiation Oncology, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Manchester, UK.
authors.forename: L K
authors.initials: LK
authors.lastname: Lee
authors.forename: C
authors.initials: C
authors.lastname: Whitehurst
authors.forename: Q
authors.initials: Q
authors.lastname: Chen
authors.forename: M L
authors.initials: ML
authors.lastname: Pantelides
authors.forename: F W
authors.initials: FW
authors.lastname: Hetzel
authors.forename: J V
authors.initials: JV
authors.lastname: Moore
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017323:Dihematoporphyrin Ether / Q000627:therapeutic use*; D004285:Dogs; D008297:Male; D009336:Necrosis; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011467:Prostate / Q000473:pathology / Q000528:radiation effects; D011469:Prostatic Diseases / Q000188:drug therapy* / Q000473:pathology
chemical_list: D000970:Antineoplastic Agents; D017319:Photosensitizing Agents; D017323:Dihematoporphyrin Ether