Intraprostatic distribution and long term follow-up after AdV-tk immunotherapy as neoadjuvant to surgery in patients with prostate cancer

A phase I-II study to evaluate gene mediated cytotoxic immunotherapy in newly diagnosed prostate cancer before radical prostatectomy was conducted in Monterrey, Mexico. METHODS: To investigate delivery of adenovirus to the prostate, fluorescently labeled vector was injected into fresh prostatectomy specimens and distribution visually analyzed. The optimal volume and site instillation was then used for transrectal ultrasound guided intraprostatic injection in 10 patients with adenocarcinoma scheduled for radical prostatectomy. Each received 2-apical and 2-basal 0.5 ml injections of AdV-tk for a total of 1×10(11) vp followed by 14 days of prodrug. Nine patients continued to tumor resection: 6 high-risk, 1 intermediate and 2 low-risk. In-vivo vector distribution was analyzed from resected tissue of four patients. Patients were monitored for tumor progression and acute and long-term safety. RESULTS: Two apical and two basal injections of 0.5ml led to optimal organ-wide distribution of an adenoviral vector ex-vivo and in-vivo. Cytotoxicity was evidenced by transient rise in PSA and tumor histology. There were no significant adverse events deemed related to the treatment and no late toxicities after median follow up of 11.3 years. All six high-risk patients had positive surgical margins and one had seminal vesicle involvement. Despite slow PSA rise post-surgery in 3 of these patients, none developed metastases. The intermediate and low-risk patients had complete resections and none have progressed. CONCLUSION: In-vivo transrectal ultrasound guided instillation of an adenoviral vector into four sites in the prostate was practical as an outpatient procedure, well tolerated and led to distribution throughout the intraprostatic tumor mass. AdV-tk demonstrated no significant acute or late toxicities. Trends in PSA and disease progression conveyed the possibility of a sustained immune response against residual disease.