Local tumour progression after ultrasound-guided microwave ablation of liver malignancies: risk factors analysis of 2529 tumours.

OBJECTIVES: To identify the incidence and risk factors that predict local tumour progression (LTP) after ultrasound-guided percutaneous microwave ablation (MWA) of liver malignancies. MATERIALS AND METHODS: One thousand two hundred and nine patients with 2,529 malignant nodules (mean size 2.8 ± 1.4 cm, range 0.9-8.0 cm) were treated by MWA between July 2005 and December 2012. The influence of 11 factors on the risk of LTP was assessed. Univariate Kaplan-Meier and Cox proportional hazard models were used for statistical analysis. RESULTS: The overall LTP was 4.2 % per tumour and 8.6 % per patient with a median follow-up of 20.3 months. LTP per tumour was 4.3 % for primary liver cancer and 4.1 % for metastases (p = 0.32). The survival of LTP and free-LTP patients at 1, 3, and 5 years was 92.4 %, 71.6 %, and 45.1 %, respectively, and 92.9 %, 70.1 %, and 52.4 %, respectively (p = 0.93). By univariate analysis, tumour location, size and ablation time were significant risk factors of LTP. Multivariate analysis identified tumour size (>3.0 cm) to be the only independent predictor of LTP. CONCLUSIONS: MWA of liver malignancies achieves a relatively low-incidence LTP, although LTP risk significantly increases if tumour size >3.0 cm. The technique seems to be appropriate even for patients with a tumour at a risk location. KEY POINTS: • Microwave ablation of liver malignancies achieves a low incidence local tumour progression. • LTP risk significantly increases if the tumour size is >3.0 cm. • MWA seems to be appropriate even for patients with a tumour at a risk location.