Purpose: To assess the ability to deliver full-thickness bladder wall cryoablation through a cystoscopic approach using a new closed-loop 6F cryocatheter and thermal dose-controlled protocol. Materials and Methods: Evaluations were conducted using a chronic porcine model wherein 10 lesions/animal were created throughout the bladder (bladder wall, trigone region, ureteral orifice, and distal ureter). A 6F cryocatheter was passed through the working channel of a flexible cystoscope. Single 1- and 1.5-minute freeze protocols in a saline environment were evaluated and resultant lesion size was determined. A laparoscopic approach was utilized to observe the transmural extension of the ice propagation. Results: Studies demonstrated the generation of transmural lesions characterized by full-thickness histologic necrosis after freezing for 1.5 minutes regardless of tissue thickness (range 2-12 mm). All animals were found to have good overall health (maintained weight, appetite, mobility, and energy levels) throughout the recovery period. No significant deviations were noted in complete blood count and serum chemistry bloodwork except for elevated creatine kinase levels. Importantly, no fistulas or perforations were noted. Conclusions: The cryocatheter was able to rapidly and effectively freeze the bladder wall through a cystoscopic approach. The results showed the ability to consistently ablate an ∼1 cm diameter and up to 1.2 cm deep using a single 1.5-minute freeze protocol. Analysis of the ablation efficacy revealed ∼80% destruction within the frozen mass. Although further testing and refinement are needed, these studies demonstrate the potential of this new approach to provide a next-generation strategy for the treatment of bladder cancer.
Keywords: bladder cancer; cryoablation; cryotherapy; cystoscopy.