Thermal Characterization and Preclinical Validation of an Accessible, Carbon Dioxide-Based Cryotherapy System

To investigate the potential of an affordable cryotherapy device for accessible treatment of breast cancer, the performance of a novel carbon dioxide-based device was evaluated through both benchtop and in vivo canine models. This novel device was quantitatively compared to a commercial device that utilizes argon gas as the cryogen. The thermal behavior of each device was characterized through calorimetry and by measuring the temperature profiles of iceballs generated in tissue phantoms. A 45-minute treatment from the carbon dioxide device in a tissue phantom produced a 1.67 +/- 0.06 cm diameter lethal isotherm that was equivalent to a 7-minute treatment from the commercial argon-based device which produced a 1.53 +/- 0.15 cm diameter lethal isotherm. In vivo validation was performed with the carbon dioxide-based device in one spontaneously occurring canine mammary mass with two standard 10-minutes freezes. Following cryotherapy, this mass was surgically resected and analyzed for necrosis margins via histopathology. The histopathology margin of necrosis from the in vivo treatment with the carbon dioxide device at 14 days post cryoablation was 1.57 cm. While carbon dioxide gas has historically been considered an impractical cryogen due to its low working pressure and high boiling point, this study shows that carbon dioxide-based cryotherapy may be equivalent to conventional argon-based cryotherapy in the size of the ablation zone in a standard treatment time. The validation of the carbon dioxide device performed in this study is an important step towards bringing accessible breast cancer treatment to women in low-resource settings.