To evaluate the efficacy of ultrasound-guided microwave ablation combined with hepatic artery chemoembolization (TACE) in the treatment of liver metastases from colorectal cancer with different diameters and identify the factors affecting the prognosis.

A retrospective analysis was performed on 122 patients with liver metastases from colorectal cancer who underwent TACE, ultrasound-guided microwave ablation, or the combination of the two at Gansu Provincial Hospital from January 2016 to January 2019. According to the maximum diameter of the metastasis, the patients were divided into either a ≤3 cm group (group A; 57 cases) or a ＞3, ≤5 cm group (group B; 65 cases). The efficacy of the three treatment methods in group A and group B was observed. The chi-square test or Fisher's exact probability test was used to compare the difference in treatment efficiency and disease control rate among the three treatment methods. The Kaplan-Meier method was used to plot the survival curves of the three treatment methods and calculate the cumulative survival at 1, 2, and 3 years after treatment. The log-rank test was used to compare the difference in cumulative survival rate among the three treatments, and the COX regression model was used to analyze the factors affecting the prognosis of colorectal cancer liver metastasis.

In group A, the treatment efficiency, disease control rate, cumulative survival rate, and recurrence rate were comparable between patients receiving combination therapy and those receiving microwave ablation therapy (P＞0.05). The treatment effective rate, disease control rate, and cumulative survival rate associated with combination therapy and microwave ablation therapy were significantly higher [95.2% vs 91.3% vs 64.0%; 100% vs 95.7% vs 72.0%; (100%, 95.6%, 55.7%) vs (100%, 92.3%, 24.2%) vs (95.1%, 59.5%, 0%)], and the recurrence rate (21.1% vs 22.2% vs 65.0%) was significantly lower than those with TACE treatment (effective rate: χ²=6.546, 5.056, P=0.013, 0.039; disease control rate: both P=0.011; cumulative survival rate: χ²=19.256, 7.651, P＜0.001,=0.006; recurrence rate: P=0.006, 0.008). In group B, the effective rate, disease control rate, and cumulative survival rate associated with combination therapy were significantly higher [94.4% vs 70.9% vs 38.5%; 97.2% vs 80.6% vs 57.7%; (100%, 91.3%, 11.7%) vs (95.5%, 71.1%, 4.5%) vs (91.5%, 34.0%, 0%)], and the recurrence rate (36.0% vs 68.2% vs 94.4%) was significantly lower than those with microwave ablation therapy or TACE therapy (effective rate: χ²=6.690, 22.964, P=0.018, ＜0.001; disease control rate: P=0.043, ＜0.001; cumulative survival rate: χ²=5.511, 24.469, P=0.019, ＜0.001; recurrence rate: P=0.028, ＜0.001). The effective rate, disease control rate, and cumulative survival rate associated with microwave ablation therapy were significantly higher, and the recurrence rate was significantly lower than those with TACE therapy (effective rate: χ²=6.068, P=0.020; disease control rate: χ²=3.159, P=0.046; cumulative survival rate: χ²=5.429, P=0.020; recurrence rate: P=0.039). Multivariate COX regression analysis showed that the maximum diameter of metastases (RR=3.360, Ρ＜0.001), lesion number (RR=2.210, Ρ=0.022), pre-treatment chemotherapy (RR=0.979, Ρ=0.001), degree of differentiation (highly differentiated: RR=0.103, Ρ＜0.001), and treatment methods (combination therapy or microwave ablation treatment: RR=0.044, 0.174, Ρ＜0.001) were independent factors affecting the prognosis of liver metastases from colorectal cancer.

Microwave ablation combined with TACE under ultrasound guidance has obvious advantages in the treatment of ＞3-5 cm colorectal cancer liver metastasis, which can significantly prolong the survival time. The larger the diameter and number of the metastatic foci, the worse the prognosis of the patients. Combination therapy or ultrasound-guided microwave ablation therapy, combined with pre-treatment chemotherapy, can increase survival rate and improve prognosis.