Objective: Historically, radiofrequency ablation (RFA) of hepatic tumors has been limited by the size of the index tumor, with difficulty in treating tumors larger than 3cm. The recently introduced multiple-electrode RFA system has the potential of generating large ablation volumes and thus, allowing treatment of larger tumors. Our goal is to determine the feasibility and safety of multiple-electrode RFA of hepatic tumors, and to compare ablation volumes based on number of electrodes used.

Methods: We performed a retrospective review of percutaneous RFA of 36 hepatic tumors ranging in diameter 0.9cm-5.4cm and involving 22 patients. Tumors smaller than 2 cm were treated with a single electrode (10 tumors) and larger tumors were treated with 2 electrodes (16 tumors) or 3 electrodes (10 tumors). Electrodes were positioned 1-2cm apart to create an intratumoral configuration that maximized index tumor coverage. CT or MR imaging was obtained within 24 hours of ablation and further imaging at 3-6 months thereafter. Number of electrodes, ablation volume, maximum size of ablation and maximum size of tumor were compared among three probe groups. Complications were defined using NCI’s Common Terminology Criteria for Adverse Events (CTCAE v.3.0).

Results: The mean maximum size of the tumors ablated with 1, 2, and 3 electrodes was 1.2cm, 2.7cm, and 3.4cm; respectively. The mean volume of ablation with 2 electrodes (40.9cm³) and 3 electrodes (86.6cm³) was significantly increased compared to 1 electrode (11.7cm³); p≤0.0004 among comparisons. Four of 31 tumors (13%) with adequate follow-up imaging developed local recurrence (mean follow-up 6.7 months). No major complications (CTCAE≥3) occurred that were directly attributable to the RFA procedure. One patient underwent bile duct intervention 31 days following RFA. This patient then developed an abscess at the RFA site and subsequently died of sepsis.

Conclusions: Multiple-electrode RFA of hepatic tumors is technically feasible and provides the benefit of large ablation zones and, thus, greater confidence in treating larger tumors. While we encountered no major complications directly attributable to RFA, we caution against bile duct manipulation following RFA.