Objective: To elucidate if a nonpositive <1-cm resection margin has any effect on hepatic recurrence in patients undergoing liver resection for colorectal liver metastases. Patients and methods: Six hundred and nine patients underwent 663 liver resections. Patients with positive margin were excluded from the analysis. Two groups were studied: group A, <1-cm resection margin and group B, ≥1-cm resection margin. Results: A total of 545 liver resections in 523 patients were carried out with nonpositive resection margins. With a median follow-up of 25 months, the 5-year cumulative hepatic recurrence reached 54% in group A (n = 206) and 41% in group B (n = 339). Factors associated with hepatic recurrence were synchronic metastases (P = 0.0015), bilobar (P < 0.001), two or more metastases (P < 0.001), margin <1 cm (P = 0.0123) and extrahepatic disease (P = 0.0037). A strong correlation between resection margin and number of metastases was confirmed (P < 0.001). At multivariate analysis only two factors were independent predictors of hepatic recurrence: multinodular disease in the liver specimen [≥4 metastases hazard ratio (HR) = 3.45; 95% confidence interval (CI): 2.2–5.38; P < 0.001] and extrahepatic disease at hepatectomy (HR = 1.58; 95% CI: 1.58–3.32). Conclusion: Subcentimeter nonpositive resection margins do not directly influence hepatic recurrence in patients undergoing hepatectomy for colorectal liver metastases.

To evaluate whether a bipolar saline-enhanced radiofrequency (RF) ablation system embedded in one needle is able to consistently produce homogeneous and predictable areas of coagulation necrosis with or without the Pringle maneuver of vascular inflow occlusion. RF ablation (480 kHz) of the liver was performed in 24 healthy pigs by means of laparotomy: group A (n = 5), 4-cm distance between electrodes 1 and 2; group B (n = 7), 4-cm distance and the Pringle maneuver; group C (n = 5), 2-cm distance; and group D (n = 7), 2-cm distance with the Pringle maneuver. Twenty percent NaCl solution was infused continuously at a rate of 100 mL/h via each electrode during the procedure. The pigs were followed up, and they were euthanized on the 7th day. Livers were removed for histologic assessment. Time, impedance, current, power output, specific voltage of the contacts, energy output, temperatures in the liver, volume of the lesion, and energy delivered per lesion volume were determined and compared among groups. Predictability of lesion volume was evaluated with the coefficient of variability. Mean values of the variables were compared among the groups by means of one-way analysis of variance or Kruskall-Wallis test. Impedance at the end of the RF ablation procedure was almost twofold lower than the corresponding initial value in all groups. In Pringle groups B and D, regular ellipsoids of coagulation necrosis were created (mean lesion volume, 149.50 cm3 +/- 34.26 and 69.43 cm3 +/- 15.48, respectively). In non-Pringle groups A and C, the shape of coagulation necrosis was influenced by the vessels encountered, and mean lesion size was lower than that in the Pringle groups (P <.01). The coefficient of variability of lesion size was lower in the Pringle groups (23% and 22%, respectively) than that in the non-Pringle groups (75% and 30%, respectively). The bipolar saline-enhanced RF ablation method produces homogeneous and predictable areas of coagulation necrosis between two electrodes, regardless of the distance between them, preferably with vascular inflow occlusion.

Irreversible electroporation (IRE) has gained attention as a new non-thermal therapy for ablation with important benefits in terms of homogeneous treatment and fast recovery. In this study, a new concept of high voltage generator is used, enabling irreversible electroporation treatment in large tissue volume using parallel plates. Unlike currently available generators, the proposed versatile structure enables delivering high-voltage high-current pulses. To obtain homogeneous results, 3-cm parallel-plates electrodes have also been designed and implemented. IRE ablation was performed on six female pigs at 2000 V/cm electric field, and the results were analysed after sacrifice three hours, three days and seven days after ablation. Histopathological and ultrastructural studies, including transmission and scanning electron microscopy, were carried out. The developed high-voltage generator has proved to be effective for homogeneous IRE treatment using parallel plates. The destruction of the membrane of the hepatocytes and the alterations of the membranes of the cellular organelles seem incompatible with cell death by apoptosis. Although endothelial cells also die with electroporation, the maintenance of vascular scaffold allows repairing processes to begin from the third day after IRE as long as the blood flow has not been interrupted. This study has opened new direction for IRE using high performance generators and highlighted the importance of taking into account ultrastructural changes after IRE by using electron microscopy analysis.