Abstract: We included one randomised clinical trial that compared four groups: electro-coagulation alone, electro-coagulation + dimethyl sulphoxide, electro-coagulation + allopurinol, and control (Salim 1993). The risk of bias in the trial is high. In three groups, patients had their metastases destroyed with diathermy electro-coagulation (current set at No 5) and received: 1) solution of allopurinol by mouth 5 mL 4 x a day or 2) allopurinol by mouth 5 mL (50 mg) 4 x a day or 3) dimethyl sulphoxide by mouth 5 mL (500 mg) 4 x a day. In the control group patients received a solution of allopurinol by mouth 5 mL 4 x a day. The treatment was started in the fifth postoperative day and was continued for five years. Three hundred and six patients who had undergone resection of the sigmoid colon and who had five or more hepatic metastases were included; 75 received electro-coagulation alone (58 were evaluable), 76 received electro-coagulation plus allopurinol (53 were evaluable), 78 received electro-coagulation plus dimethyl sulphoxide (57 were evaluable), and 77 were in the control group (55 evaluable). The authors reported the number of deaths due to disease spread (100% in the control, 98% in electro-coagulation, 87% in electro-coagulation + allopurinol, and 86% in the electro-coagulation + dimethyl sulphoxide groups). There was a significant benefit in favour of the electro-coagulation + allopurinol (risk ratio (RR) 0.87 (95% confidence interval (CI) 0.78 to 0.96)) and electro-coagulation + dimethyl sulphoxide (RR 0.86 (95% CI 0.77 to 0.95)) groups compared to the control group, but no such benefit in the electro-coagulation alone group (RR 0.98 (95% CI 0.95 to 1.02)) compared to the control group. There were no local recurrences, no positive tests for occult blood, and observed pulmonary metastases were always with ultrasonographic evidence of hepatic secondaries and were not significantly different for the experimental groups compared to the control group (electro-coagulation: RR 1.11 (95% CI 0.4 to 3.09)), electro-coagulation + allopurinol (RR 0.86 (95% CI 0.28 to 2.66)), electro-coagulation + dimethyl sulphoxide (RR 0.8 (95% CI 0.26 to 2.48)). None of the adverse events were significantly associated with treatment. On the basis of one randomised trial which did not describe its methodology in sufficient detail to assess risk of bias and quality, excluded 27% of patients after randomisation due to various reasons, and is probably not free from selective outcome reporting bias, there is insufficient evidence to conclude that in patients with colonic cancer liver metastases, electro-coagulation alone brings any significant benefit in terms of survival or recurrence compared with the control. In addition, there is insufficient evidence for the effectiveness of adding allopurinol or dimethyl sulphoxide to electro-coagulation. The probability for selective outcome reporting bias in the trial is high. More randomised trials are needed in order to sufficiently validate electro-coagulation with or without co-interventions.

Plain-language summary: One randomised clinical trial was included comparing four arms: electro-coagulation alone, electro-coagulation + dimethyl sulphoxide, electro-coagulation + allopurinol and control. The treatment was started in the fifth postoperative day and was continued for five years. Three hundred and six patients were included, but only 223 could be included in the analyses. On the basis of one randomised trial, which did not describe its methodology in sufficient detail to assess risk of bias and quality, excluded 27% of patients after randomisation due to various reasons, and is probably not free from selective outcome reporting bias, there is insufficient evidence to conclude that in patients with colonic cancer liver metastases, electro-coagulation alone brings any significant benefit in terms of survival or recurrence compared with the control group. In addition, there is insufficient evidence for the effectiveness of adding allopurinol or dimethyl sulphoxide to electro-coagulation.