High-Resolution Ultrasound Allows Percutaneous Initiation and Surveillance of Prostate Cancer in an Orthotopic Murine Model

Introduction: Prostate cancer xenografts should prefer or- thotopic growth to subcutaneous tumors as the former more closely mimics the natural tumor environment. However, these models are technically demanding and require an invasive laparotomy. To overcome these problems, we evaluated a minimally invasive approach by performing per- cutaneous prostate puncture under the control of high-res- olution ultrasound imaging. Materials and Methods: Ortho- topic tumor cell inoculation was performed in two groups of mice, i.e. in 10 nude mice via ultrasound-guided inoculation and in another 10 nude mice via an open surgical approach. Tumor growth was monitored after 4, 5 and 6 weeks by means of a high-resolution ultrasound system. Results: High-resolution ultrasound allowed exact tumor growth monitoring. After ultrasound-guided inoculation, 8 of 10 an- imals showed tumor engraftment. The surgical procedure was successful in 9 of 10 animals. Tumor volume was slightly but not significantly greater after surgical tumor induction. Our work demonstrates that tumor cell inoculation via per- cutaneous puncture of the prostate is feasible, less time-consuming and minimally invasive compared to an open surgi- cal approach. This reduces the animal burden. Conclusion: Although the tumor size and the precision of inoculation is lower compared to the open surgical technique, this novel procedure enables real-time prostate punctures, suggesting the feasibility of other procedures including biopsy and local drug applications.