Radiofrequency and Microwave Ablation Compared to Systemic Chemotherapy and to Partial Hepatectomy in the Treatment of Colorectal Liver Metastases: A Systematic Review and Meta-Analysis

Abstract

Purpose: To assess safety and outcome of radiofrequency ablation (RFA) and microwave ablation (MWA) as compared to systemic chemotherapy and partial hepatectomy (PH) in the treatment of colorectal liver metastases (CRLM).

Methods: MEDLINE, Embase and the Cochrane Library were searched. Randomized trials and comparative observational studies with multivariate analysis and/or matching were included. Guidelines from National Guideline Clearinghouse and Guidelines International Network were assessed using the AGREE II instrument.

Results: The search revealed 3530 records; 328 were selected for full-text review; 48 were included: 8 systematic reviews, 2 randomized studies, 26 comparative observational studies, 2 guideline-articles and 10 case series; in addition 13 guidelines were evaluated. Literature to assess the effectiveness of ablation was limited. RFA + systemic chemotherapy was superior to chemotherapy alone. PH was superior to RFA alone but not to RFA + PH or to MWA. Compared to PH, RFA showed fewer complications, MWA did not. Outcomes were subject to residual confounding since ablation was only employed for unresectable disease.

Conclusion: The results from the EORTC-CLOCC trial, the comparable survival for ablation + PH versus PH alone, the potential to induce long-term disease control and the low complication rate argue in favour of ablation over chemotherapy alone. Further randomized comparisons of ablation to current-day chemotherapy alone should therefore be considered unethical. Hence, the highest achievable level of evidence for unresectable CRLM seems reached. The apparent selection bias from previous studies and the superior safety profile mandate the setup of randomized controlled trials comparing ablation to surgery.

Keywords: Colorectal liver metastases (CRLM); Microwave ablation (MWA); Partial hepatectomy (PH); Radiofrequency ablation (RFA); Systemic chemotherapy.

Fig. 1

Results of selection: effectiveness of thermal ablation versus surgical resection or systemic chemotherapy in treating patients with CRLM

Fig. 2

Risk of bias of included reviews for RFA

Fig. 3

Risk of bias of Ruers et al. [29]

Fig. 4

Risk of bias of comparative observational studies for RFA

Fig. 5

RFA versus PH alone: overall survival (OS)

Fig. 6

RFA + PH versus PH alone: overall survival (OS)

Fig. 7

RFA versus PH alone: 30-day mortality

Fig. 8

RFA + PH versus PH alone: 60-day mortality

Fig. 9

RFA + PH versus PH alone: 90-day mortality

Fig. 10

RFA versus PH alone: complication rate

Fig. 11

RFA versus PH alone: disease-free survival (DFS)

Fig. 12

RFA versus PH alone: local progression-free survival (LPFS)

Fig. 13

RFA + PH versus PH alone: disease-free survival (DFS)

Fig. 14

RFA + PH versus PH alone: local progression-free survival (LPFS)

Fig. 15

Risk of bias of Shibata et al. [48]

Fig. 16

Risk of bias of observational studies for MWA

Fig. 17

Risk of bias of case series for MWA