Cryoablation: physical and molecular basis with putative immunological consequences

Cryoablation (CA) is unique as the singular energy deprivation therapy that impacts all cellular processes. CA is independent of cell cycle stage and degree of cellular stemness. Importantly, CA is typically applied as a non-repetitive (single session) treatment that does not support adaptative mutagenesis as do many repetitive therapies. CA is characterized by the launch of multiple forms of cell death including (a) ice-related physical damage, (b) initiation of cellular stress responses (kill switch activation) and launch of necrosis and apoptosis, (c) vascular stasis, and (d) likely activation of ablative immune responses. CA is not without limitation related to the thermal gradient formed between cryoprobe surface (∼-185°C) and the distal surface of the freeze zone (∼0°C) requiring freeze margin extension beyond the tumor boundary (up to ∼1 cm). This limitation is mitigated in part by commonly applied dual freeze thaw cycles and the use of freeze sensitizing adjuvants. This review will (1) identify the cascade of damaging effects of the freeze-thaw process, its physical and molecular-based relationships, (2) a likely immunological involvement (abscopic effect), and (3) explore the use of freeze-sensitizing adjuvants necessary to limit freezing beyond the tumor margin.