Abstract: We included one randomised clinical trial with 61 participants (43 male and 18 female) with colorectal cancer with liver metastases: 22 received transarterial embolisation (TAE; hepatic artery embolisation), 19 received transarterial chemoembolisation (TACE; 5-fluorouracil hepatic artery infusion chemotherapy with degradable microspheres), and 20 received 'no active therapeutic intervention' as a control. Most tumours were synchronous, unresectable metastases involving up to 75% of the liver. Participants were followed for a minimum of seven months. The trial was at high risk of bias. Very-low-certainty evidence found inconclusive results for mortality at 44 months between the TAE and TACE versus no intervention groups (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.74 to 1.06; 61 participants). Local recurrence was reported in 10 participants without any details about the group allocation. Very-low-certainty evidence found little or no difference in mortality between the TAE and no intervention groups (RR 0.91, 95% CI 0.75 to 1.10; 42 participants). Median survival was 7 months from trial entry (range 2 to 44 months) in the TAE group and 7.9 months (range 1 to 26 months) in the control group, and 8.7 months after diagnosis (range 2 to 49 months) in the TAE group and 9.6 months (range 1 to 27 months) in the control group. The trial authors reported the differences were not statistically significant. There were no reported side effects in the control group. In the TAE group, 18 participants experienced short-term symptoms of 'post-embolisation syndrome', which were relieved with symptomatic treatment; one participant also had a local puncture site haematoma. Very-low-certainty evidence found little or no difference in mortality between the TACE and no intervention groups (RR 0.83, 95% CI 0.65 to 1.07; 39 participants). Median survival in the TACE group was 10.7 months (range 3 to 38 months) from trial entry, and 13.0 months (range 3 to 38 months) after diagnosis. The trial authors reported that differences between groups were not statistically significant. All participants experienced short-term nausea, with or without vomiting, immediately after treatment; one participant developed a wound infection, and one developed deep vein thrombosis. The trial did not measure failure to clear liver metastases, time to progression of liver metastases, tumour response measures, or health-related quality of life. Cancer Research Campaign, a non-profit organisation, provided a grant for the trial; Pharmacia Ltd. delivered the Port-a-Cath arterial delivery systems and degradable starch microspheres. We identified one ongoing trial comparing TACE plus chemotherapy versus chemotherapy alone in people with unresectable colorectal liver metastases who failed with first-line chemotherapy (NCT03783559). Based on one, small randomised trial at high risk of bias, the evidence is very uncertain about the effect of TAE or TACE versus no active therapeutic intervention on mortality for people with liver metastases as the true effect may be substantially different. The trial did not measure failure to clear liver metastases, time to progression of liver metastases, tumour response measures, or health-related quality of life. Short-term, minor adverse events were recorded in the intervention groups only. Large trials, following current standards of conduct and reporting, are required to explore the benefits and harms of TAE or TACE compared with no intervention or placebo in people with resectable and unresectable liver metastasis.

Plain-language summary: We last searched for evidence on 20 December 2019. We included one randomised trial from earlier searches. This trial randomly assigned people with colorectal liver metastases that could not be surgically removed, to one of three intervention groups: TAE (22 participants), TACE (19 participants), and a control group (20 participants) that received no active therapeutic intervention. Cancer Research Campaign, a non-profit organisation, provided a grant for the study; Pharmacia Ltd. delivered the Port-a-Cath arterial delivery systems and degradable starch microspheres. Trial participants were followed for a minimum of seven months. Mortality at 44 months from trial entry was 86% in the TAE group, 79% in the TACE group, and 95% in the control group. Median survival after trial entry was 7.0 months in the TAE group, 10.7 months in the TACE group, and 7.9 months in the control group. Median survival from diagnosis was 8.7 months in the TAE group, 13.0 months in the TACE group, and 9.6 months in the control group. Local recurrence was reported in 10 participants, without further details of their treatment group. None of the participants in the control group reported side effects; 82% of the TAE group experienced short-term pain, nausea, vomiting, and high temperature, which got better with symptomatic treatment, and there was one report of bruising at the puncture site. TACE recipients reported short-term nausea, with or without vomiting, after most of the treatment sessions, and short-lived pain or discomfort; there was one wound infection, and one case of deep vein thrombosis. All the results were inconclusive between groups. The evidence from one small randomised clinical trial showed neither beneficial nor harmful effects of TAE or TACE compared to no intervention, in people with liver metastases, measured by mortality. We did not find data on the other outcomes of interest. We judged the evidence to be of very low certainty. The identified trial was small, at high risk of bias, and with inconclusive results.