Transarterial (chemo)embolisation versus systemic chemotherapy for colorectal cancer liver metastases

The liver is affected by two groups of malignant tumours: primary liver cancers and liver metastases. Liver metastases are significantly more common than primary liver cancer, and five-year survival after radical surgical treatment of liver metastases ranges from 28% to 50%, depending on primary cancer site. However, R0 resection (resection for cure) is not feasible in most people; therefore, other treatments have to be considered in the case of non-resectability. One possible option is based on the concept that the blood supply to hepatic tumours originates predominantly from the hepatic artery. Transarterial chemoembolisation (TACE) of the peripheral branches of the hepatic artery can be achieved by administering a chemotherapeutic drug followed by vascular occlusive agents and can lead to selective necrosis of the cancer tissue while leaving normal liver parenchyma virtually unaffected. The entire procedure can be performed without infusion of chemotherapy and is then called bland transarterial embolisation (TAE). These procedures are usually applied over a few sessions. Another possible treatment option is systemic chemotherapy which, in the case of colorectal cancer metastases, is most commonly performed using FOLFOX (folinic acid, 5-fluorouracil, and oxaliplatin) and FOLFIRI (folinic acid, 5-fluorouracil, and irinotecan) regimens applied in multiple sessions over a long period of time. These therapies disrupt the cell cycle, leading to death of rapidly dividing malignant cells. Current guidelines determine the role of TAE and TACE as non-curative treatment options applicable in people with liver-only or liver-dominant metastatic disease that is unresectable or non-ablatable, and in people who have failed systemic chemotherapy. Regarding the treatment modalities in people with colorectal cancer liver metastases, we found no systematic reviews comparing the efficacy of TAE or TACE versus systemic chemotherapy.

To evaluate the beneficial and harmful effects of transarterial embolisation (TAE) or transarterial chemoembolisation (TACE) compared with systemic chemotherapy in people with liver-dominant unresectable colorectal cancer liver metastases.

We searched the Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE, Embase, and three additional databases up to 4 April 2024. We also searched two trials registers and the European Medicines Agency database and checked reference lists of retrieved publications.

We included randomised clinical trials assessing beneficial and harmful effects of TAE or TACE versus systemic chemotherapy in adults (aged 18 years or older) with colorectal cancer liver metastases.

We used standard Cochrane methods. Our primary outcomes were all-cause mortality; overall survival (time to mortality); and any adverse events or complications. Our secondary outcomes were cancer mortality; health-related quality of life; progression-free survival; proportion of participants dying or surviving with progression of the disease; time to progression of liver metastases; recurrence of liver metastases; and tumour response measures (complete response, partial response, stable disease, and progressive disease). For the purpose of the review and to perform necessary analyses, whenever possible, we converted survival rates to mortality rates, as this was our primary outcome. For the analysis of dichotomous outcomes, we used the risk ratio (RR); for continuous outcomes, we used the mean difference; and for time to event outcomes, we calculated hazard ratios (HRs), all with 95% confidence intervals (CI). We used the standardised mean difference with 95% CIs when the trials used different instruments. We used GRADE to assess the certainty of evidence for each outcome. We based our conclusions on outcomes analysed at the longest follow-up.

We included three trials with 118 participants randomised to TACE versus 120 participants to systemic chemotherapy. Four participants were excluded; one due to disease progression prior to treatment and three due to decline in health. The trials reported data on one or more outcomes. Two trials were performed in China and one in Italy. The trials differed in terms of embolisation techniques and chemotherapeutic agents. Follow-up ranged from 12 months to 50 months. TACE may reduce mortality at longest follow-up (RR 0.86, 95% CI 0.79 to 0.94; 3 trials, 234 participants; very low-certainty evidence), but the evidence is very uncertain. TACE may have little to no effect on overall survival (time to mortality) (HR 0.61, 95% CI 0.37 to 1.01; 1 trial, 70 participants; very low-certainty evidence), any adverse events or complications (3 trials, 234 participants; very low-certainty evidence), health-related quality of life (2 trials, 154 participants; very low-certainty evidence), progression-free survival (1 trial, 70 participants; very low-certainty evidence), and tumour response measures (presented as the overall response rate) (RR 1.81, 95% CI 1.11 to 2.96; 3 trials, 234 participants; very low-certainty evidence), but the evidence is very uncertain. No trials reported cancer mortality, proportion of participants dying or surviving with progression of the disease, and recurrence of liver metastases. We found no trials comparing the effects of TAE versus systemic chemotherapy in people with colorectal cancer liver metastases.

The evidence regarding effectiveness of TACE versus systemic chemotherapy in people with colorectal cancer liver metastases is of very low certainty and is based on three trials. Our confidence in the results is limited due to the risk of bias, inconsistency, indirectness, and imprecision. It is very uncertain whether TACE confers benefits with regard to reduction in mortality, overall survival (time to mortality), reduction in adverse events or complications, improvement in health-related quality of life, improvement in progression-free survival, and tumour response measures (presented as the overall response rate). Data on cancer mortality, proportion of participants dying or surviving with progression of the disease, and recurrence of liver metastases are lacking. We found no trials assessing TAE versus systemic chemotherapy. More randomised clinical trials are needed to strengthen the body of evidence and provide insight into the benefits and harms of TACE or TAE in comparison with systemic chemotherapy in people with liver metastases from colorectal cancer.