Ablative Margins of Colorectal Liver Metastases Using Deformable CT Image Registration and Autosegmentation

Percutaneous image‐guided ablation for hepatic metastases

“…For CLM, it has been shown that minimum ablation margins of at least 5 mm and ideally 10 mm are critical for prolonged local tumour progression-free survival, regardless of the thermal ablation modality used (RFA or MWA). 5,[12][13][14][15]17,18,[55][56][57][58] This is referred to as an A0 ablation, analogous to surgical resections with clear microscopic margins (R0) and is essential to provide local cure and serve as a surgical alternative, since the majority of intrahepatic micrometastases are within 1 cm of the gross tumour. 59 When a 10 mm minimal margin can be achieved, local tumour progression free-survival exceeds 95% and can offer a chance for local cure similar to surgery, without the associated morbidity.…”

“…Current practices include 3D software assessments of the ablation zone and margins. 16,18,55,[61][62][63] These assessments have higher discrimination power to detect areas of insufficient tumour coverage by the ablation zone than 2D imaging alone and can provide intraoperative feedback regarding areas with suboptimal coverage that can be re-ablated in the same setting. 16,55,[61][62][63] Although recent evidence indicates that the intraprocedural 3D assessment is more sensitive than the first post-ablation imaging for the detection of insufficient margins that can predict local tumour progression, 64 historically the technical efficacy of ablation relied on a 4-8 weeks postablation contrast-enhanced CT or MRI with contrast.…”

“…5,14,72 Though a wide range of local tumour progression rates have been reported in the early experience with ablation for CLM (2-60%), ablations with margins ≥5 mm and with histologically proven tumourfree ablation zones (as seen on immediate post-ablation biopsies) have local tumour progression rates that are similar to those reported for wedge or anatomic liver resections (0-7%). 13,14,18 A recent retrospective study showed zero cases of local tumour progression of CLM when a minimal ablation margin ≥5 mm was achieved, as quantified using 3D software with biomechanical deformable CT image registration. 18 A phase II randomized controlled clinical trial showed prolonged progression-free survival in patients with initially unresesctable CRC liver metastases undergoing RFA (with or without hepatic resection) plus standard of care chemotherapy (FOLFOX), compared to chemotherapy alone.…”

“…13,14,18 A recent retrospective study showed zero cases of local tumour progression of CLM when a minimal ablation margin ≥5 mm was achieved, as quantified using 3D software with biomechanical deformable CT image registration. 18 A phase II randomized controlled clinical trial showed prolonged progression-free survival in patients with initially unresesctable CRC liver metastases undergoing RFA (with or without hepatic resection) plus standard of care chemotherapy (FOLFOX), compared to chemotherapy alone. 75 A subsequent study in the same cohort with longer follow-up demonstrated significantly prolonged overall survival in the combination arm, with 8-year survival rates of 36% versus 9% in the systemic treatment arm.…”

“…10 With careful patient selection and appropriate technique allowing for the creation of ablation zones with adequate minimum ablation margins (≥5 mm, ideally ≥10 mm), local tumour control is similar to that observed after limited resection. 5,6,[11][12][13][14][15][16][17][18][19] The available evidence and outcomes following ablation of the most frequently encountered types of hepatic metastases in clinical practice are reviewed. Patient selection, ablative techniques, complications and follow-up considerations are discussed.…”