Vascular‐targeted photodynamic therapy (padoporfin, WST09) for recurrent prostate cancer after failure of external beam radiotherapy: a study of escalating light doses

Abstract

OBJECTIVE: To report on the efficacy of TOOKAD® (WST 09; NegmaLerads, Magny‐Les‐Hameaux, France) vascular‐targeted photodynamic therapy (VTP) as a method of whole‐prostate ablation in patients with recurrent localized prostate cancer after the failure of external beam radiotherapy (EBRT). PATIENTS AND METHODS: Patients received a fixed photosensitizer dose of 2 mg/kg and patient‐specific light doses as determined by computer‐aided treatment planning. Up to six cylindrical light‐diffusing delivery fibres were placed transperineally in the prostate under ultrasonographic guidance. The treatment response was assessed by measuring serum prostate‐specific antigen (PSA) levels, lesion formation (avascular areas of tissue) measured on 7‐day gadolinium‐enhanced T1‐weighted magnetic resonance imaging (MRI) and a 6‐month biopsy. RESULTS: Treatment of the whole prostate was possible with minimal effects on surrounding organs. An increased light dose improved the tissue response, with MRI‐detectable avascular lesions, encompassing up to 80% of the prostate in some patients. A complete response, as determined by the 6‐month biopsy, required that patients received light doses of at least 23 J/cm 2 in 90% of the prostate volume (D 90 > 23 J/cm 2 ). Of the 13 patients who received at least this light dose, eight were biopsy‐negative at 6 months. In this group of eight patients, PSA levels decreased and did so to negligible levels for those patients with a baseline PSA level of <5 ng/mL. Side‐effects were modest and self‐limited in most patients; there were recto‐urethral fistulae in two patients, one of which closed spontaneously. CONCLUSIONS: TOOKAD‐VTP can produce large avascular regions in the irradiated prostate, and result in a complete negative‐biopsy response at high light doses. A response rate of more than half for those patients receiving the highest light doses shows the clinical potential of TOOKAD‐VTP to manage recurrence of prostatic carcinoma after EBRT.