Robot-assisted laparoscopic high-intensity focused ultrasound for focal therapy of prostate: novel approach.

Abstract

Focal therapy for prostate cancer is an experimental approach, and the best candidate for the focal targeted therapy continues to evolve along with the development of therapeutic modalities. HIFU delivers ultrasonic energy to a focal area of tissue with resultant local heat and complete coagulative necrosis. 1–4 Transrectal HIFU has been proven to be capable of providing long-term local control of prostate cancer. 5–7 A novel FDA (510k)-cleared laparoscopic HIFU probe for soft tissue ablation has been developed (Sonatherm laparoscopic probe; SonaCare Medical LLC, Indianapolis, IN, USA; Fig. 1a,b). This device has an 11-mm shaft that delivers continuous HIFU-energy in direct contact with the target tissues to ablate 1 cc of tissue per minute (extremely powerful compared with the conventional transrectal HIFU), and could provide a new opportunity for focal HIFU with a laparoscopic approach in conjunction with pelvic lymphadenectomy for precise staging and additional therapeutic benefit in non-low-risk prostate cancer. The aims of the present study were to show the technical feasibility and precision of the laparoscopic HIFU approach for targeted focal ablation to the predetermined image-visible lesion, using a posterior approach from the Denonvilliers’ space for the PZ tumor and an anterior approach from the Retzius space for the TZ tumor. Three fresh male cadavers were used for the present study in accordance with all institutional review board ethical requirements. Under transrectal US guidance, gold fiducials (0.9 mmdiameter × 3 mm-length; CIVCO Medical Solutions, Kalona, IA, USA) were implanted in the left posterior (PZ; n = 3) and right anterior (TZ; n = 3) of the cadaver prostates to serve as the center of a virtual tumor. Transperitoneal laparoscopic access was obtained using a da Vinci (Intuitive Surgical, Sunnyvale, CA, USA) robot-assisted approach. Through a posterior approach by the incision of the posterior vesical peritoneum, Denonvilliers’ fascia was incised and the prostate was released from the anterior surface of the rectum towards the apex. The HIFU probe was placed between the rectum and prostate to target PZ tumors (Fig. 1c). An anterior approach through the Retzius space was used to target TZ tumors (Fig. 1d). During the anterior approach, a4 × 4-inch dry gauze was tamponed posterior to the prostate to protect the rectal wall from any risk of accidental injury caused by HIFU energy penetrating through the prostate. The HIFU probe was placed in direct contact with the surface of the targeted zone with coupling assistance between the device and the prostate surface by US jelly, and the virtual tumor was set as the center of the ablation zone. The virtual tumor was identified as a hyperechoic lesion on real-time US. Robotic bilateral pelvic lymph node dissection was carried out with an extended pattern template. Gross inspection and histological evaluation of the prostate and the periprostate anatomy were carried out. A 3-mm step-sectional analysis of the prostate was carried out to measure the size of coagulative necrosis of the HIFU lesion and to identify the proximity of the fiducial to the center of the HIFU lesion. Placement of the laparoscopic HIFU probe using the posterior approach (for PZ tumors) and anterior approach (for TZ tumors) was feasible in all cases. The simultaneous display of both the initial planning and real-time monitoring US images confirmed the targeting precision. The average time for the total HIFU procedure was 18 min (range 10–31 min), including all steps of coupling realignment, targeting and ablation. The surgical time was approximately 1–1.5 h (including access, ablation and lymph-node dissection). Step-sectional analysis of the prostate showed histological evidence of the ablative zone, with