Apoptosis Post Microwave Ablation of the Liver: Does it Change with Power?

Abstract

Apoptosis is a type of the delayed or indirect cellular responses that happen after microwave ablation. It helps eradicate the few cancer cells that might survive the applied heat during cancer ablation. The extent of its expression is yet to be defined. Aims: We investigated whether the ablation power made any difference to the expression of apoptosis in the ablated and normal areas. Methods: Ablations with 50W, 70W, and 90W powers were created in three ex vivo perfused porcine livers. Biopsies were collected from the lesions and were assessed with Hematoxylin-Eosin and immunohistochemistry (Caspase 3 and M30) looking for apoptosis in each zone (central necrotic zone [CNZ], transitional zone [TZ], and normal surrounding zone [NZ]). Statistical analysis was performed using ANOVA and t-test. Results: None of the CNZ showed expression of Caspase-3. In the TZ, there was significant difference between 50W and 90W (P = 0.009), but not between 50W and 70W (P = 0.8), or between 70W and 90W (P = 0.4). In the NZ, a highly significant difference was noted between 50W and 90W (P = 0.003), a significant difference between 50W and 70W (P = 0.01), but not between 70W and 90W (P = 0.06). For M30, no expression of M30 was noted in all necrotic zones. A significant difference was noted between 50W and 90W (P = 0.02). There were no significant differences between 50W and 70W (P = 0.4) or between 70W and 90W (P = 0.07). Conclusion: Increasing power enhances apoptosis in the ablated areas. This response can be an adjunct for eradicating cancer cells that might escape the heat in the ablated zones.