Cryotherapy and radiofrequency ablation: pathophysiologic basis and laboratory studies

There is increasing interest in minimally invasive alternatives to surgery, especially as the natural history of small renal masses appears in the majority to be that of very slow growth. Cryoablation and radiofrequency ablation are two energy-based therapies that can be applied in a minimally invasive manner. We will review the recent clinical and laboratory studies that have formed the scientific foundation of the current clinical protocols and how these protocols may change in light of recent observations.

Although there is literature supporting enhanced cell death with the use of a passive thaw in cryoablation, recent data suggest that the use of an active thaw is no different. The active thaw process will effectively cryoablate renal tissue as well as significantly reduce overall operative time. There is lack of uniformity in the effectiveness of radiofrequency ablation for renal masses. It has been concluded that hematoxylin and eosin staining is inadequate for assessment of cell viability after radiofrequency ablation and thus, nicotinamide adenine dinucleotide staining should be included in the histological assessment of tissue.

Cryoablation is the most studied modality and its ability to both directly and indirectly damage cells is generally understood. Clinical experience will further refine knowledge about optimal freezing temperature and freeze-thaw cycles. The coagulation necrosis of radiofrequency ablation is an effective means of destroying cancerous tissue but targeting this energy has been difficult and treatment failures have occurred.