Introduction:
The liver remains the most frequent site of metastases from colorectal cancer (CRC). The purpose of this retrospective study was to compare the combination therapy of transarterial chemoembolization (TACE) and microwave ablation (MWA) with MWA as monotherapy in treating liver metastases from CRC (LMCRC).

Methods:
A total of 251 patients with unresectable LMCRC not responding to chemotherapy were enrolled. Group A consisted of 184 patients (104M and 80W; mean age: 64±11.4 years) with 442 metastases who received the combination therapy of TACE+MWA. Sixty-seven patients (49M and 18W; mean age: 63.2±11.8 years) with 173 metastases were included in group B, who were treated by MWA as monotherapy. The parameters evaluated were metastasis diameter, complications, diameter of ablation zone 24h post-MWA, local tumor progression (LTP), hepatic distant tumor progression (hDTP), hepatic progression-free survival (hPFS), and overall survival (OS).

Results:
The mean metastasis diameter was 2.3 cm in group A and 2.2 cm in group B (p-value: 0.24). There were no major complications reported. The mean diameter of the ablation zone was significantly larger in group A at 5.1 cm compared to 4.9 cm in group B (p-value: 0.039). The LTP rate was 4.9 % in group A and 4.5 % in group B (p-value: 0.062). The hDTP rate was 71.7% and 83.6% for groups A and B, respectively (p-value: 0.81). The mean hPFS was significantly longer in group A at 13.8 months compared to 8.1 months in group B (p-value: 0.03). The median OS time for group A was 30 months and 26 months for group B (p-value: 0.67). The 1- and 2-year OS rates were 84.2% and 61.1% for group A and 82.3% and 53.2% for group B, respectively.

Conclusions:
The combination therapy of TACE and MWA is superior to the MWA monotherapy for LMCRC, mainly according to the size of ablation zone, hDTP, hPFS and OS.