Stereotactic Radiofrequency Ablation: Providing New Dimensions in Interventional Oncology

Abstract

Purpose: Radiofrequency ablation (RFA) has become widely accepted as the first-line local tumor therapy of surgical untreatable primary and secondary liver malignancies. Main risk factors for residual tumor and local recurrence are tumor size (> 3cm), imprecise probe placement and insufficient overlapping of multiple ablation spheres. Our aim was to evaluate if stereotactic RFA may improve the results of conventional techniques. Materials/Methods: Stereotactic RFA of 92 primary and 67 secondary liver tumors in 68 patients was performed. After general anesthesia the patient was rigidly immobilized on the CT table. A contrast-enhanced helical CT scan (2 mm slice thickness) was obtained with respiratory triggering. Pathways for multiple probes were planned on a navigation system in order to cover the whole tumor volume by overlapping necroses. Depending on the size of the tumor (0.5-11 cm, mean: 2.9 cm) pathways for the placement of 1-24 probes were planned. After registration a targeting device was adjusted for every path. In maximal expiration one after another coaxial needle was advanced to the preplanned depth. A native control CT was performed for verification of needle placement. RFA followed subsequently. Residual tumor was determined on a contrast-enhanced CT after 1 month, recurrence on CTs at 3 months intervals (mean follow-up: 9.2 months). Results: Residual tumor was found in 12/159 lesions (2.7%) of which 10 could be successfully retreated. Recurrences were found in 12/147 (8.2%) lesions, of which 3 were successfully re-ablated. Recurrence rate for lesions < 3 cm (n=92) was 4.3%, 3-5 cm (n=48) was 12.5% and > 5 cm (n=19) was 10.5%. Conclusion: Stereotaxy allows for precise positioning and 3D-distribution of RFA probes in order to achieve an overlapping ablation zone for even large lesions. It decreases the local tumor recurrence rate as compared to conventional CT/US-guided RFA.