Abstract: One randomised clinical trial fulfilled the inclusion criteria of the review. Forty participants with multiple liver metastases of colorectal cancer and no evidence of extrahepatic disease were randomly assigned. Thirty of these participants (14 females and 16 males) were included in the analysis: 14 participants received microwave coagulation and 16 underwent conventional surgery (hepatectomy or liver resection). The diagnosis of colorectal cancer (Stage IB to IIIC; tumour (T)2 node (N)0 to T3N2) and liver metastases was confirmed by histological assessment. Mean participant age was 61 years. The tumours were resectable. The risk of bias in the trial was judged to be high. Participants were followed for three years. Mortality at the last follow-up was 64% (9/14) in the microwave group and 75% (12/16) in the conventional surgery group (risk ratio (RR) 0.86; 95% confidence interval (CI) 0.53 to 1.39), that is, no significant difference was observed. In the microwave coagulation group, 71%, 57%, and 14% survived 1, 2, and 3 years, and in the conventional surgery group, the percentages were 69%, 56%, and 23%. The hazard ratio calculated using the Parmar method was 0.91 (0.39 to 2.15). Mean survival time was 27 months in the microwave group and 25 months in the conventional surgery group, and the mean disease-free interval was 11.3 months in the microwave group and 13.3 months in the hepatectomy group. Differences for both outcomes were not statistically significant. Reported frequency of adverse events was similar between the microwave coagulation and conventional surgery groups, except for the required blood transfusion, which was more common in the conventional surgery group. No intervention-related mortality was observed. After treatment, the carcinoembryonic antigen level decreased significantly in both groups. On the basis of one randomised clinical trial, which did not describe allocation concealment or blinding, and which excluded from analysis 25% of participants after random assignment, evidence is insufficient to show whether microwave coagulation brings any significant benefit in terms of survival or recurrence compared with conventional surgery for participants with liver metastases from colorectal cancer. The number of adverse events, except for the requirement for blood transfusion, which was more common in the liver resection group, was similar in both groups. At present, microwave therapy cannot be recommended outside randomised clinical trials.

Plain-language summary: One randomised clinical trial comparing microwave coagulation with conventional surgery (liver resection) is included in the review: 14 participants received microwave coagulation and 16 participants underwent conventional surgery. The trial was judged to have a high risk of systematic error (ie, overestimation of benefits and underestimation of harms). On the basis of one randomised trial, which did not describe allocation concealment or blinding, and which excluded from analysis 25% of participants after random assignment, evidence is insufficient to show whether microwave coagulation provides any significant benefit in terms of survival or recurrence compared with conventional surgery for participants with liver metastases from colorectal cancer. The number of adverse events, except for the requirement for blood transfusion, which was more common in the liver resection group, was similar in both groups. At present, microwave therapy cannot be recommended outside randomised clinical trials.