• Hepatobiliary cancer
• liver

We read with interest the article by Auernhammer and Göke1 on therapeutic strategies for liver metastasis in neuroendocrine carcinomas. Local tumour progress following radiofrequency ablation (RFA) occurred in only 6% of neuroendocrine carcinomas, but no data on overall survival and prognostic factors following RFA were available. As another thermal ablative technique for liver cancer, microwave ablation (MWA), which uses electromagnetic energy to rapidly rotate adjacent polar water molecules to achieve primarily active heating, shows the following advantages: higher intratumorous temperatures, larger ablation volumes, shorter ablation time and simultaneously multiple probe deployment.2 3 We wish to report an incidence of MWA treatment for primary liver cancer and to examine additional factors that affect survival.

A large database with 1007 patients (1363 nodules) was generated in seven Chinese centres between January 2005 and July 2010. Criteria for radical treatment were as follows: a single lesion of 8 cm or smaller, three or fewer multiple lesions with a maximum diameter of 4 cm or less and absence of portal vein cancerous thrombus or extrahepatic metastases (those who did not meet the criteria received palliative treatment). All the patients were percutaneously treated by a cooled-shaft microwave system (KY-2000, Kangyou Medical, Nanjing city, China) consisting of a 15-G needle antenna and a 20-G thermocouple under ultrasound guidance.

The median follow-up period for all patients was 17.3 months (range 3–68.9 months). All patients (mean age 56.3 years (range 21–90 years), 819 men) underwent a mean of 1.2±0.4 sessions (total 1643 sessions, range 1–4 sessions) for each nodule with a median ablation time of 7.5 min (range 2.0–60.9 min). Eight hundred and fifty-five patients were Child class A, 124 were Child class B and 28 were Child class C. Of 1007 patients, 754 had one nodule and 253 had multiple nodules. The mean diameter of the nodule was 2.9±1.8 cm (range 1.0–18.5 cm), with 904 (66.3%) nodules ≤3 cm and 459 (33.7%) nodules >3 cm. Nine hundred and seventy (96.3%) patients underwent radical MWA (figure 1) and others received palliative treatment.

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Figure 1

Transverse images in a 41-year-old man with a single focus of hepatocellular carcinoma (HCC; 2.5×2 cm) and accompanying cirrhosis. (A) Contrast-enhanced MRI scan obtained before ablation shows a well-demarcated tumour (arrow) adjacent to liver hilum with hyperintensity at arterial phase. (B) Transverse arterial phase MRI scan obtained 24 months after ablation shows a hypointense ablation zone (arrow) at the site of the treated tumour, suggesting the absence of new tumour progress. (C) Transverse venous phase MRI scan obtained 24 months after ablation shows the hypointense ablation zone (arrow) adjacent to the large vessel of the liver hilum.

Overall, the 1-, 3- and 5-year cumulative survival rates were 91.2%, 72.5% and 59.8%, respectively. For patients who underwent radical treatment, the 1-, 3- and 5-year cumulative survival rates were 92.9%, 74.1% and 61.2%, respectively. The 1-, 3- and 5-year cumulative survival rates for patients with a single nodule (92.8%, 77.7% and 65.8%, respectively) were significantly higher than those for patients with multiple nodules (85.6%, 55.4% and 41%, respectively) (p<0.001). Technique effectiveness was 97.1% (1276/1363), and local tumour progress occurred in 5.9% (78/1363) of the tumours. Intrahepatic metastasis occurred in 40.8% (411/1007) of the patients, and extrahepatic metastasis occurred in 10.4% (105/1007) of the patients. The treatment-related death rate was 0.4% (4/1007), and major complications occurred in 2.2% (36/1643). Multivariate analysis using the Cox proportional hazards regression model showed that sex (p=0.016), tumour size (p<0.001), tumour number (p<0.001), tumour type (p=0.039), Child–Pugh classification (p<0.001), preablation α-fetoprotein level (p=0.004), liver cirrhosis (p=0.019) and postablation extrahepatic metastasis (p<0.001) were independent unfavourable prognostic factors (table 1).

The 5-year survival result in the present study is comparable to resection and transplantation4 5 and has a slight advantage over the RFA, ethanol injection and non-cooled-tip MWA treatment.6–8 The optimistic results may be attributed to the following reasons. First, cooled-shaft MWA shows higher thermal efficiency, thus producing a larger ablation zone and becoming less prone to convective heat loss from blood flow with ablation zone remaining uniform,3 which may be attributable to low local tumour progress, especially for tumours adjacent to large vessels (only 6.6% per tumour). Second, the simultaneous treatment of multiple tumours is feasible with multiple microwave antennae, which shortens the treatment time and leads to a synergistically larger elliptical-shaped ablation zone for round and large tumours.

This large-scale study shows that ultrasound-guided percutaneous cooled-tip MWA is effective and safe in treating patients with primary liver cancer with favourable local tumour control and long-term outcomes.