Interstitial photodynamic therapy in the canine prostate

• Published in: British Journal of Urology 1997-12, Vol.80 (6), p.898-902
• Main Authors: LEE, L.K., WHITEHURST, C., CHEN, Q., PANTELIDES, M.L., HETZEL, F.W., MOORE, J.V.
• Format: Article
• Language: English
• Subjects: Animals; Antineoplastic Agents - therapeutic use; Biological and medical sciences; Dihematoporphyrin Ether - therapeutic use; Diseases of the urinary system; Dogs; interstitial laser therapy; Male; Medical sciences; Necrosis; Photochemotherapy - methods; Photodynamic therapy; Photosensitizing Agents - therapeutic use; Prostate - pathology; Prostate - radiation effects; prostate carcinoma; Prostatic Diseases - drug therapy; Prostatic Diseases - pathology; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects)
• ISSN: 0007-1331; 1464-410X
• DOI: 10.1046/j.1464-410X.1997.00460.x

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. Materials and 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. Conclusion  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.