Liver cancer: Increased microwave delivery to ablation zone with ooled shaft antenna - Experimental and clinical studies

Purpose: To prospectively investigate whether the ablation zone induced with microwaves could be increased by delivering greater energy with a cooled-shaft antenna. Materials and Methods: All studies were animal care and ethics committee approved. Written informed consent was obtained from all patients. Microwave ablation was performed by using a cooled-shaft antenna in 48 ex vivo and 12 in vivo experiments with porcine livers. The coagulation diameters achieved in different microwave ablation parameter groups (60-90 W for 5-25 minutes) were compared. Ninety patients (78 men, 12 women; mean age, 53 years; age range, 20-82 years) with 133 0.8-8.0-cm (mean, 2.7 cm +/- 1.5 [standard deviation]) primary or metastatic liver cancers were treated with the same microwave ablation technique. Complete ablation (CA) and local tumor progression (LTP) rates were determined. Generalized estimating equations were used to compare differences in tumor size, ablation zone diameter, and CA and LTP rates between different patient subgroups. Results: In the ex vivo livers, in vivo livers, and liver cancers, one application of microwave energy with 80W for 25 minutes produced mean coagulation diameters of 5.6 x 7.4 cm, 3.5 x 5.9 cm, and 3.6 x 5.0 cm, respectively. Skin burn was not observed. CA rates in small (<= 3.0-cm), intermediate (3.1-5.0-cm), and large (5.1-8.0-cm) liver cancers were 94% (81 of 86), 91% (31 of 34), and 92% (12 of 13), respectively. During a mean follow-up period of 17.4 months, LTP occurred in seven (5%) treated cancers. There was a significant difference in LTP rate between the cirrhosis and no-cirrhosis groups (P = .03). Four patients had major complications. Conclusion: Delivery of greater microwave energy with cooled-shaft antennas yielded large ablation zones in ex vivo and in vivo livers and in liver cancers. Effective local tumor control was achieved during one microwave ablation session. (c) RSNA, 2007.