Hepatic Ablation Promotes Colon Cancer Metastases in an Immunocompetent Murine Model

Objective: To determine the impact of radiofrequency (RF) and microwave (MW) energy compared to direct cautery on metatstatic colon cancer growth. Background: Hepatic ablation with MW and RF energy creates a temperature gradient around a target site with temperatures known to create tissue injury and cell death. In contrast, direct heat application (cautery) vaporizes tissue with a higher site temperature but reduced heat gradient on surrounding tissue. We hypothesize that different energy devices create variable zones of sublethal injury that may promote tumor recurrence. To test this hypothesis we applied MW, RF, and cautery to normal murine liver with a concomitant metastatic colon cancer challenge. Methods: C57/Bl6 mice received hepatic thermal injury with MW, RF, or cautery to create a superficial 3-mm lesion immediately after intrasplenic injection of 50K MC38 colon cancer cells. Thermal imaging recorded tissue temperature during ablation and for 10 seconds after energy cessation. Hepatic tumor location and volume was determined at day 7. Results: Cautery demonstrated the highest maximum tissue temperatures (129 degrees C) with more rapid return to baseline compared toMWor RF energy. All mice had metastasis at the ablation site. Mean tumor volume was significantly greater in theMW(95.3mm(3); P = 0.007) and RF (55.7mm(3); P = 0.015) than cautery (7.13mm(3)). There was no difference in volume between MW and RF energy (P = 0.2). Conclusions: Hepatic thermal ablation promotes colon cancer metastasis at the injury site. MV and RF energy result in greater metastatic volume than cautery. These data suggest that the method of energy delivery promotes local metastasis.