Efficacy and safety of cryoablation procedures using mouse models of bladder cancer

The standard treatment for muscle-invasive bladder cancer (MIBC), total cystectomy, is highly invasive. Decreased quality of life (QOL) due to urinary diversion is a serious problem in patients with MIBC. In this study, we examined the therapeutic efficacy of cryoablation for MIBC in a mouse model of orthotopic bladder cancer and investigated its usefulness as a new treatment modality. Murine bladder cancer models were established by administering the chemical carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine. We monitored physiological parameters, including body weight, water intake, urine output, and urination frequency. Cryoablation was then performed on the tumor-bearing mice, and postoperative tissue changes were assessed histologically. Physiological responses were tracked for up to 28 days post-surgery and compared with those in a non-surgical control group. Additionally, levels of CD4 ⁺ and CD8 ⁺ T cells were measured to evaluate immune activation following cryoablation. After cryoablation in the bladder cancer mouse model, we observed the following: i) localized frostbite-induced injury to the muscle layer, which was gradually replaced by adjacent tissue; ii) preservation of spontaneous urination post-surgery; and iii) no procedure-related mortality. Moreover, a significant increase in CD4 ⁺ and CD8 ⁺ T cells was detected 28 days after cryoablation. The efficacy, safety, and immune activation potential of cryoablation were confirmed in an orthotopic murine model of bladder carcinoma. Cryoablation for MIBC shows promise as a novel therapeutic approach, not only as a radical, bladder-sparing treatment, but also as a form of combination immunotherapy with the potential to reduce metastatic disease.