Image-Guided Ablation for Colorectal Liver Metastasis: Principles, Current Evidence, and the Path Forward

Abstract

Image-guided ablation can provide effective local tumor control in selected patients with CLM. A randomized controlled trial suggested that radiofrequency ablation combined with systemic chemotherapy resulted in a survival benefit for patients with unresectable CLM, compared to systemic chemotherapy alone. For small tumors, ablation with adequate margins can be considered as an alternative to resection. The improvement of ablation technologies can allow the treatment of tumors close to major vascular structures or bile ducts, on which the applicability of thermal ablation modalities is challenging. Several factors affect the outcomes of ablation, including but not limited to tumor size, number, location, minimal ablation margin, RAS mutation status, prior hepatectomy, and extrahepatic disease. Further understanding of the impact of tumor biology and advanced imaging guidance on overall patient outcomes might help to tailor its application, and improve outcomes of image-guided ablation.

Ablation therapy for patients with colorectal liver metastases with and without extrahepatic metastases: evaluation of long-term outcomes and prognostic factors

“…The optimal patient for ablation has a single or few small metastases and disease limited to the liver. However, our study contributes with evidence that patients with limited and/or controllable extrahepatic metastases may benefit from ablation, though less than patients without extrahepatic metastases as found in other studies [20][21][22]. With a propensity score matched analysis, we found a decreased survival for patients with extrahepatic metastases.…”

Percutaneous ablation of liver metastases from colorectal cancer: a comparison between the outcomes of ultrasound guidance and CT guidance using propensity score matching

“…Peripheral rim enhancement after RFA might mask some small residual tumors [ 21 ]. Fourth, the evaluation of the ablation area on CT might be imperfect if it is not performed by a three-dimensional assessment, which can be limited by the misalignment of the liver due to patient’s position, respiratory phase, tissue attenuation changes after ablation, or image resolution [ 20 , 22 , 23 ]. The hyperechoic halo around the ablation area on US with real-time and flexible orthogonal planes and the use of a contrast agent could increase conspicuousness and make the extent more clearly and reliably identifiable [ 24 , 25 ].…”

“…Although the lesion around the needle was ablated, it is possible that some micro-lesions metastasized along the previous needle track or the injured intra-hepatic vessels adjacent to the tumors [19]. Second, electrode placement, which is a prerequisite factor for ablation, under US guidance might be more centered or "suitable" within the target lesion compared with CT guidance, covering the whole lesion more sufficiently with overlapping ablation areas [20]. Third, the partial volume effect, slice thickness, or metal artifacts on CT might interfere with the determination of tiny lesion residue.…”

Irreversible electroporation for the management of pancreatic cancer: Current data and future directions

“…A major limitation of IRE is the intent of producing a small ablation zone of approximately 1-1.5 cm, which requires several electrodes to produce the desired A0 ablation. This requirement renders the procedure more technically demanding and time-consuming compared to conventional thermal ablation modalities[ 54 ]. Future research should focus on the standardization and optimization of an IRE treatment protocol for the treatment of pancreatic cancer with the goal of providing maximum efficacy without damaging surrounding tissues.…”