Presented Wednesday, 05 September 2007 at the 29th Congress of the Societe International d'Urologie - SIU 2007 - Optimizing Clinical Outcomes in Prostate and Renal Cell Carcinomas - The Second Annual Symposium on Advanced GU Malignancy - Palais des Congres de Paris, France

Introduction and Objectives: Tookad (WST09) is a novel bacteriochlorophyl derived intravascular photosensitizer. When activated by 763nm laser light it destroys prostate cancer by damaging its blood supply. It then clears within 90 minutes. We studied the safety and efficacy of this form of Vascular Targeted Phototherapy (VTP) in men with recurrent prostate cancer after external beam radiation therapy (EBRT) after an initial failure of VTP.

Material & Methods: We investigated the effect of increasing light delivered from 4 -6 interstitial prostate source fibers at a fixed Tookad dose of 2 mg/kg in 8 men with recurrent prostate cancer after radiation who had failed an initial treatment with Tookad VTP. Initial VTP treatment had been with Tookad at 2 mg/kg and variable amount of light. Light was measured in the prostate, urethra and rectum to monitor safety and efficacy. Treatment efficacy was assessed by 1-wk dynamic contrast enhanced MRI, by serial serum PSA determinations, and 6 month multi-core biopsy.

Results: Total light energy delivered previously to the prostate averaged 63 J/cc with a range of 41 to 83 J/cc. Retreatment light energy delivered was significantly higher at a mean of 215 J/cc. Tookad-VTP retreatment was easily performed and generally well tolerated. The majority of patients were discharged within 24 hours. MRI total prostate devascularization response in the initial treatment was 16.4% and ranged from 7% to 34% of the entire prostate. The mean retreatment response 46.9%. An average 6-month PSA decrease of 66% (range 1% - 99%) from baseline was measured, with several patients achieving undetectable PSA. MR and PSA response correlated directly with energy delivered. Pathological correlation with PSA and MR changes remain to be determined. In spite of extensive prostate defects at MRI voiding function was minimally affected in the majority of patients. There was 1 significant adverse outcome, a urethro-rectal fistula.

Conclusions: Tookad-VTP for recurrent prostate cancer after radiation can be readministered safely. Increased light dose appears to increase the likelihood of increased efficacy. The ability to retreat with Tookad VTP suggests that a strategy of sequential targeted treatments of small tumors might be feasible.

Authors: Trachtenberg J, Elhilali M

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