Volumetric 3D assessment of ablation zones after thermal ablation of colorectal liver metastases to improve prediction of local tumor progression

Computational modeling of microwave ablation of lung tumors: Assessment of model-predictions against post-treatment imaging

BACKGROUND

Percutaneous microwave ablation is a clinically established method for treatment of unresectable lung nodules. When planning the intervention, the size of ablation zone, which should encompass the nodule as well as a surrounding margin of normal tissue, is predicted via manufacturer-provided geometric models, which do not consider patient-specific characteristics. However, the size and shape of ablation is dependent on tissue composition and properties and can vary between patients.

PURPOSE

To comparatively assess performance of a computational model-based approach and manufacturer geometric model for predicting extent of ablation zones following microwave lung ablation procedures on a retrospectively collected clinical imaging dataset.

METHODS

A retrospective computed-tomography (CT) imaging dataset was assembled of 50 patients treated with microwave ablation of lung tumors at a single institution. For each case, the dataset consisted of a pre-procedure CT acquired without the ablation applicator, a peri-procedure CT scan with the ablation applicator in position, and post-procedure CT scan to assess the ablation zone extent acquired on the first follow-up visit. A physics-based computational model of microwave absorption and bioheat transfer was implemented using the finite element method, with the model geometry incorporating key tissue types within 2 cm of the applicator as informed by imaging data. The model-predicted extent of the ablation zone was estimated using the Arrhenius thermal damage model. The ablation zone predicted by the manufacturer geometric model consisted of an ellipsoid registered with the applicator position and dimensions provided by instructions for use documentation. Both ablation estimates were compared to ground truth ablation zone segmented from post-procedure CT via Dice similarity coefficient (DSC) and average absolute error (AAE). The statistically significant difference at level 0.05 in performance between both ablation prediction methods was tested with permutation test on DSC as well as AAE datasets with applied Bonferroni multiple-comparison correction.

RESULTS

Receiver operating characteristic analysis of the predictive power of the volume of insufficient coverage (i.e. tumor volume which did not receive an ablative thermal dose) as an indicator of local tumor recurrence yielded an area under the curve of 0.84, illustrating the clinical significance of accurate prediction of ablation zone extents. Across all cases, AAEs were 3.65 ± 1.12 mm, and 5.11 ± 1.93 mm for patient-specific computational and manufacturer geometric models respectively. Similarly, average DSCs were 0.55 ± 0.14, and 0.46 ± 0.19 for computational and manufacturer geometric models respectively. The manufacturer geometric model overpredicted volume of the ablation zone compared to ground truth by 141% on average, whereas the patient-specific computational model overpredicted ablation zone volumes by 31.5% on average.

CONCLUSIONS

Patient-specific physics-based computational models of lung microwave ablation yield improved prediction of microwave ablation extent compared to the manufacturer geometric model.

Immediate changes in MRI signals after the MRI-guided microwave ablation of malignant liver tumors

OBJECTIVE

To observe the immediate changes in MRI signals after the MRI-guided microwave ablation of malignant liver tumors and to explore the pattern of immediate signal changes post-ablation.

MATERIALS AND METHODS

A retrospective analysis was conducted on 23 patients with 27 lesions who underwent MRI-guided liver microwave ablation at Baoshan people's Hospital from September 2022 to December 2023. The relationship between the changes in MRI signals and time post-ablation was studied. The first scan was performed immediately after ablation (designated as 0 min) and followed by scans at 3 min, 6 min, 10 min, 15 min, 20 min, and 30 min post-ablation. The signal characteristics that changed in each sequence after each scan were measured and recorded.

RESULTS

After ablation, the mean maximum diameter of the high-signal range in 27 T1WI ablation foci varied over a short period of time (0 min: 22.00 mm; at 3 min: 26.58 mm; at 6 min: 26.94 mm; at 10 min: 27.06 mm; at 15 min: 27.12mm; at 20 min: 27.16 mm; and at 30 min: 27.16 mm). The change from 0-10 min was statistically significant (t = -10.326, P < 0.001), whereas the change from 10-30 min was not statistically significant (t = -1.536, P = 0.068). And, the signal intensity increased over time. The signal intensity of the primary lesion remained unchanged while the range decreased. There were minimal differences in the range and intensity changes in the T2-weighted imaging (T2WI) sequence. In diffusion-weighted imaging (DWI), the lesions showed high-signal intensity pre-ablation, but in post-ablation, it exhibited a high-signal surrounding the ablation zone with iso-intense or mixed signals, and the apparent diffusion coefficient (ADC) value increased.

CONCLUSION

The high-signal range observed in the T1WI sequence at the 10th min scan after the ablation completely reflected the true extent of the ablated foci, whereas the low-signal range in the T2WI sequence was stable and unchanged.

Transmission-Based Monitoring of Dual-Applicator Microwave Ablation Discriminates Discontiguous from Contiguous Ablation Zones in an In Vivo Porcine Liver Model

PURPOSE

To determine the technical feasibility of discriminating discontiguous from contiguous ablation zones between a pair of microwave ablation (MWA) applicators using broadband microwave transmission signal measurements in an in vivo porcine liver model.

MATERIALS AND METHODS

Dual applicator 2.45 GHz MWA was performed using 1 directional and 1 omnidirectional applicator, spaced 3 cm apart, under imaging guidance. The study involved 15 hepatic MWAs across 4 swine, with ablation durations of 200 seconds (n = 8) for discontiguous ablation and 600 seconds (n = 7) for contiguous ablation, each at 60 W; these ablation durations and applied power combinations were selected with the intent of creating discontiguous (200 s) and contiguous (600 s) ablation zones. A custom software periodically measured transmission signals between the applicators at 46-second intervals. Contrast-enhanced computed tomography (CT), gross pathology, and histopathologic analyses were used to assess the processed transmission signal (PTS).

RESULTS

Statistical analyses revealed significant differences between contiguous and discontiguous ablation zones on contrast-enhanced CT imaging (volume, 16.9 cm3 [SD ± 5.2] vs 3.9 cm3 [SD ± 1.5]; P = .0002) and gross tissue sections and histology (area, 10 cm3 [SD ± 3.3] and 6.5 cm3 [SD ± 1.3]; P = .001), and PTS datasets showed values of 85.1% (SD ± 11) and 37.3% (SD ± 12.9; P = .02). PTS values functioned well as predictors of complete versus incomplete ablation (area under the receiver operating characteristic curve, 0.90), with a PTS threshold of 53% being optimal for indicating ablation zone contiguity. Ablation zone contiguity was strongly correlated with PTS (Spearman correlation coefficient, 0.86; P < .0001).

CONCLUSIONS

This study demonstrated that PTS between dual MWA applicators can distinguish between contiguous and discontiguous ablation zones.

Quantitative Ablation Confirmation Methods in Percutaneous Thermal Ablation of Malignant Liver Tumors: Technical Insights, Clinical Evidence, and Future Outlook

Percutaneous image-guided thermal ablation is an established local curative-intent treatment technique for the treatment of primary and secondary malignant liver tumors. Whereas margin assessment after surgical resection can be accomplished with microscopic examination of the resected specimen, margin assessment after percutaneous thermal ablation relies on cross-sectional imaging. The critical measure of technical success is the minimal ablative margin (MAM), defined as the minimum distance between the tumor and the edge of the ablation zone. Traditionally, the MAM has been assessed qualitatively using anatomic landmarks, which has suboptimal accuracy and reproducibility and is prone to operator bias. Consequently, specialized software-based methods have been developed to standardize and automate MAM quantification. In this review, the authors discuss the technical components of such methods, including image acquisition, segmentation, registration, and MAM computation, define the sources of measurement error, describe available software solutions in terms of image processing techniques and modes of integration, and outline the current clinical evidence, which strongly supports the use of such dedicated software. Finally, the authors discuss current logistical and financial barriers to widespread use of ablation confirmation methods as well as potential solutions. Keywords: Ablation Techniques, CT, Image Postprocessing, Liver Supplemental material is available for this article. © RSNA, 2025.

Software-based versus visual assessment of the minimal ablative margin in patients with liver tumours undergoing percutaneous thermal ablation (COVER-ALL): a randomised phase 2 trial

BACKGROUND

Tumour coverage with an optimal minimal ablative margin is crucial for improving local control of liver tumours following thermal ablation. The minimal ablative margin has traditionally been assessed through visual inspection of co-registered CT images. However, rates of local tumour control after thermal ablation are highly variable with visual assessment. We aimed to assess the use of a novel software-based method for minimal ablative margin assessment that incorporates biomechanical deformable image registration and artificial intelligence (AI)-based autosegmentation.

METHODS

The COVER-ALL randomised, phase 2, superiority trial was conducted at The University of Texas MD Anderson Cancer Center (Houston, TX, USA). Patients aged 18 years or older with up to three histology-agnostic liver tumours measuring 1-5 cm and undergoing CT-guided thermal ablation were enrolled. Thermal ablation was performed with the aim of achieving a minimal ablative margin of 5 mm or greater. Patients were randomly assigned (1:1) to the experimental group (software-based assessment) or the control group (visual assessment) by use of dynamic minimisation to balance covariates. Randomisation was performed intraprocedurally after placement of the ablation applicator. Assessment of oncological outcomes and adverse events were masked to treatment allocation. All analyses were conducted on an intention-to-treat basis. The primary endpoint was the minimal ablative margin on post-ablation intraprocedural CT. A preplanned interim analysis for superiority was done at 50% patient enrolment. Adverse events were recorded with the Common Terminology Criteria for Adverse Events. This trial is registered with ClinicalTrials.gov (NCT04083378), and recruitment is complete.

FINDINGS

Patients were enrolled and treated with thermal ablation between June 15, 2020, and Oct 5, 2023. 26 patients were randomly assigned to the control group (mean age 58·1 [SD 14·8] years; 18 [69%] male and eight [31%] female; 11 [42%] colorectal cancer liver metastasis; median tumour diameter 1·7 cm [IQR 1·3-2·3]) and 24 to the experimental group (mean age 60·5 [14·4] years; 16 [67%] male and eight [33%] female; ten [42%] colorectal cancer liver metastasis; median tumour diameter 1·8 cm [1·5-2·5]). The interim analysis showed a mean minimal ablative margin of 2·2 mm (SD 2·8) in the control group and 5·9 mm (2·7) in the experimental group (p<0·0001), prompting halting of enrolment in the control group. A further 50 patients were enrolled to a non-randomised experimental group (mean age 56·5 [SD 11·7] years; 27 [54%] male and 23 [46%] female; 30 [60%] colorectal cancer liver metastasis; median tumour diameter 1·5 cm [IQR 1·3-2·2]); among these patients, the mean minimal ablative margin was 7·2 mm (SD 2·8). Grade 1-3 adverse events were reported in five (5%) of 100 patients: three (12%) of 26 in the control group and two (3%) of 74 in the experimental groups. No grade 4-5 adverse events or treatment-related deaths were reported.

INTERPRETATION

Software-based assessment during CT-guided thermal ablation of liver tumours is safe and significantly improves the minimal ablative margin compared to visual assessment. Adoption of software-based assessment as a standard component of thermal ablation should be considered to achieve the intended minimal ablative margin.

FUNDING

US National Institutes of Health and US National Cancer Institute.

Evaluation of navigation and robotic systems for percutaneous image-guided interventions: A novel metric for advanced imaging and artificial intelligence integration

PURPOSE

Navigation and robotic systems aim to improve the accuracy and efficiency of percutaneous image-guided interventions, but the evaluation of their autonomy and integration of advanced imaging and artificial intelligence (AI) is lacking. The purpose of this study was to evaluate the level of automation and integration of advanced imaging and artificial intelligence in navigation and robotic systems for percutaneous image-guided interventions, using established and novel metrics to categorize and compare their capabilities.

MATERIALS AND METHODS

Following PRISMA guidelines, a systematic review was conducted to identify studies on clinically validated navigation and robotic systems published between 2000 and May 2024. The PubMed, Embase, Cochrane Library, and Web of Science databases were searched. Data on navigation devices were extracted and analyzed. The levels of autonomy in surgical robotics (LASR) classification system (from 1 to 5) was used to analyze automation. A novel taxonomy, the Levels of Integration of Advanced Imaging and AI (LIAI2) classification system, was created to categorize the integration of imaging technologies and AI (from 1 to 5). These two scores were combined into an aggregate score (from 1 to 10) to reflect the autonomy in percutaneous image-guided intervention.

RESULTS

The review included 20 studies assessing two navigation systems and eight robotic devices. The median LASR score was 1 (Q1, Q3: 1, 1), the median LIAI2 score was 2 (Q1, Q3: 2, 3), and the median aggregate score was 3 (Q1, Q3: 3, 4). Only one robotic system (10 % of those reviewed) achieved the highest LASR qualification in the literature, a level 2/5. Four systems (40 %) shared the highest rating for LIAI2, which was a score of 3/5. Four systems (40 %) achieved the highest aggregate scores of 4/10.

CONCLUSION

None of the navigation and robotic systems achieved full autonomy for percutaneous image-guided intervention. The LASR and LIAI2 scales can guide innovation by identifying areas for further development and integration.

Evaluation of the Ki-67 labeling index on immediate pre-ablation biopsies as a predictive biomarker of local recurrence of colorectal cancer liver metastases

The aim of this study was to evaluate if the Ki-67 labeling index (LI) on immediate pre-ablation biopsies of colorectal liver metastases (CLM) is associated with the presence of viable tumor cells in subsequent ablation zone biopsies and/or local tumor progression-free survival (LTPFS). Biopsies of CLM were performed before and after microwave ablation (MWA), as part of a prospective clinical trial between October 2013 and May 2019. Pre-ablation biopsy slides were examined for the Ki-67 LI using light microscopy. Ablation zone biopsy specimens were evaluated for the presence of viable tumor using hematoxylin-eosin and immunohistochemistry. Differences in CLM Ki-67 LI between positive and negative for viable tumor ablation zone biopsies were assessed using the Mann-Whitney U test. Biopsy, tumor and margin data were evaluated as predictors of LTPFS using Kaplan-Meier/Cox methods. Thirty-four patients with 48 CLM underwent biopsy before and after MWA. Sufficient tissue for Ki-67 labeling was obtained in 43/48 (89.6%) CLM. Viable tumor cells were detected in 11 ablation zones (22.9%). There was no significant difference in the CLM Ki-67 LI between the positive and negative for viable tumor ablation zones (mean: 69.2% vs. 64.3% respectively, p = 0.4). Adequate ablation zone margins (> 5 mm; p = 0.029) and negative ablation zone biopsies (p = 0.009) were significant predictors of longer LTPFS. KRAS status, tumor size and Ki-67 LI were not significant predictors of LTPFS. Complete tumor ablation (with adequate margins and negative ablation zone biopsies) is the most important factor in achieving local control of CLM, even for tumors exhibiting aggressive tumor biology.

Multicenter and inter-software evaluation of ablative margins after thermal ablation of colorectal liver metastases

PURPOSE

To assess the association between minimal ablative margin (MAM) and local tumor progression (LTP) following CT-guided thermal ablation of colorectal liver metastases (CRLM) in a multicenter cohort and across two confirmation software.

MATERIALS AND METHODS

This multicenter retrospective study included patients who underwent CT-guided radiofrequency or microwave ablation for CRLM between 2009 and 2021 in three institutions. Three-dimensional (3D) MAM was retrospectively assessed using dedicated ablation confirmation software by automatic non-rigid (Ablation-fit) or semi-automatic rigid co-registration (SAFIR) of intraprocedural pre- and post-ablation contrast-enhanced CT scans by two independent reader teams blinded to patient outcomes. LTP was assessed on a per-tumor basis. Factors associated with LTP-free survival were assessed using multivariable Cox regression analysis.

RESULTS

Overall, 113 patients (mean age: 67 ± 10 years; 78 men) who underwent thermal ablation for 189 CRLM (mean diameter: 1.9 ± 1.1 cm) met the inclusion criteria. 173/189 (92%) CRLM could be successfully analyzed using both software. Over a median follow-up of 31 months (IQR: 22-47), 21 of 173 CRLM (12.1%) developed LTP. On multivariable analysis, 3D MAM was independently associated with LTP in both software (Ablation-fit: HR 0.47, 95% CI: 0.36-0.61, p < 0.001; SAFIR: HR 0.42, 95% CI: 0.32-0.55, p < 0.001). No LTP was observed in CRLM ablated with MAM ≥ 4 mm (Ablation-fit) and ≥ 5 mm (SAFIR). The per-tumor median absolute difference in MAM quantification between both software was 2 mm (IQR: 1-3).

CONCLUSION

MAM was independently associated with LTP after thermal ablation of CRLM across multicenter data and two confirmation software. Ablations achieving a MAM ≥ 5 mm were associated with local control in both software.

CLINICAL RELEVANCE STATEMENT

MAMs from intraprocedural contrast-enhanced CT were independently associated with LTP after thermal ablation of CRLM across multicenter data and two confirmation software, with a margin ≥ 5 mm associated with local control in both software.

KEY POINTS

Sufficient ablative margins are critical for local control following thermal ablation of CRLM. Intraprocedural CT-derived MAM was the only independent factor associated with LTP across two confirmation software. No LTP was observed in CRLM ablated with a MAM ≥ 5 mm.

Microwave Ablation of Refractory Oligometastatic Non-Small Cell Lung Cancer in the Liver

PURPOSE

To evaluate safety and effectiveness of microwave ablation (MWA) in the treatment of liver metastases (LMs) secondary to non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

This retrospective study included patients with NSCLC who underwent MWA of LM from March 2015 to July 2022. Local tumor progression-free survival (LTPFS) and overall survival (OS) were estimated using competing risk analysis and the Kaplan-Meier method. Postprocedural adverse events were recorded according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0.

RESULTS

Twenty-three patients with 32 LMs were treated in 27 MWA sessions. The mean dimension of the largest index tumor was 1.96 cm (SD ± 0.75). Technical success was 100%. Technical effectiveness was achieved in 26 (81.3%) of 32 tumors. The median length of follow-up was 37.7 months (interquartile range, 20.5-54.5 months). The median LTPFS was 16.3 months (95% confidence interval [CI], 7.87-44.10 months). The median OS was 31.7 months (95% CI, 11.1-65.8 months). Ablation margin was a significant factor for LTPFS, with tumors ablated without a measurable margin being more likely to progress than those with measurable margins (subdistribution hazard ratios [HRs], 0.008-0.024; P < .001). Older age (HR, 1.18; 95% CI, 1.09-1.28; P < .001) and presence of synchronous lung metastases (HR, 14.73; 95% CI, 1.86-116.95; P = .011) were significant predictors of OS. Serious adverse events (CTCAE Grade ≥3) within 30 days occurred in 2 (7.4%) of 27 sessions, including pulmonary embolus and severe abdominal pain.

CONCLUSIONS

Percutaneous MWA was a safe treatment for NSCLC LM, with longer survival noted in younger patients and those without synchronous lung tumors.

Evaluation of Local Tumor Outcomes Following Microwave Ablation of Colorectal Liver Metastases Using CT Imaging: A Comparison of Visual versus Quantitative Methods

Purpose To compare visual versus quantitative ablation confirmation for identifying local tumor progression and residual tumor following microwave ablation (MWA) of colorectal liver metastases (CRLM). Materials and Methods This retrospective study included patients undergoing MWA of CRLM from October 2014 to February 2018. Two independent readers visually assessed pre- and postprocedure images and semiquantitatively scored for incomplete ablation, using a six-point Likert scale, and extracted quantitative imaging metrics of minimal ablative margin (MAM) and percentage of tumor outside of the ablation zone, using both rigid and deformable registration. Diagnostic accuracy and intra- and interobserver agreement were assessed. Results The study included 60 patients (median age, 71 years [IQR, 60-74.5 years]; 38 male) with 97 tumors with a median diameter of 1.3 cm (IQR, 1.0-1.8 cm). Median follow-up time was 749 days (IQR, 330-1519 days). Median time to complete rigid and deformable workflows was 3.0 minutes (IQR, 3.0-3.2 minutes) and 14.0 minutes (IQR,13.9-14.4 minutes), respectively. MAM with deformable registration had the highest intra- and interobserver agreement, with Gwet AC1 of 0.92 and 0.67, respectively, significantly higher than interobserver agreement of visual assessment (Gwet AC1, 0.18; P < .0001). Overall, quantitative methods using MAM had generally higher sensitivity, of up to 95.6%, than visual methods (67.3%, P < .001), at a cost of lower specificity (40% vs 71.1%, P < .001), using deformable image registration. Conclusion Quantitative ablation margin metrics provide more reliable assessment of outcomes than visual comparison using pre- and postprocedure diagnostic images following MWA of CRLM. Keywords: Interventional-Body, Liver, Neoplasms, Ablation Techniques Supplemental material is available for this article. Published under a CC BY 4.0 license.

Impact of Power and Time in Hepatic Microwave Ablation: Effect of Different Energy Delivery Schemes

Microwave ablation often involves the use of continuous energy-delivery protocols with a fixed power and time. To achieve larger ablation zones, a range of protocols and power levels have been studied in experimental studies. The objective of the present study was to develop and experimentally evaluate the performance of a coupled computational electromagnetic-bioheat transfer model of 2.45 GHz microwave ablation under a variety of continuous and pulsed power delivery schemes. The main aim was to obtain an in-depth knowledge of the influence of energy delivery settings on ablation zone profiles and thermal damage in the peri-ablation zone. In addition to the theoretical model, we evaluated the power delivery schemes using ex vivo experiments and compared them to previously published data from in vivo experiments. The results showed slight differences in terms of the ablation zone size for different power delivery schemes under ex vivo conditions, with the applied energy level being the most important factor that determines ablation zone size; however, under in vivo conditions, applying a high-power pulse prior to and following a longer constant power application (BOOKEND 95 W protocol) presented the most favorable ablation zones. Moreover, the modeling and experimental studies identified threshold applied power and ablation times beyond which increases did not yield substantive increases in ablation zone extents.

Comparison of Effectiveness and Safety of Microwave Ablation of Colorectal Liver Metastases Adjacent versus Nonadjacent to the Diaphragm

PURPOSE

To compare the effectiveness and safety of percutaneous microwave ablation (MWA) for colorectal liver metastasis (CLM) adjacent versus nonadjacent to the diaphragm.

MATERIALS AND METHODS

This was a retrospective analysis of a prospectively created MWA database, from 2 prospective clinical trials for patients with CLM treated in a single tertiary center from 2012 to 2023. CLM adjacent to the diaphragm was defined as a tumor located <1 cm from the diaphragm. Minimal ablation margin (MM) was calculated with 3-dimensional software using postablation contrast-enhanced computed tomography (CT). Adverse events were assessed with Common Terminology Criteria for Adverse Events (CTCAE) v5.0 classification for 6 months.

RESULTS

Two hundred nine CLMs underwent 191 MWA sessions in 143 patients. Mean tumor diameter was 1.52 cm (SD ± 0.53). Eighty-three of 209 (39.7%) CLMs were adjacent to the diaphragm. There was no difference in local tumor progression-free survival (LTPFS) between CLMs adjacent and nonadjacent to the diaphragm (hazard ratio [HR], 0.65; 95% CI, 0.37-1.16; P = .15). MMs of 5-10 mm and >10 mm were documented in 49.3% versus 46.8% (P = .83) and 21.6% versus 12.6% (P = .16) for CLMs adjacent versus nonadjacent to the diaphragm, respectively. Twelve-month LTPFS was similar between groups (HR, 0.65; 95% CI, 0.37-1.16; P = .15) without local tumor progression for MM of >10 mm. There were 3 Grade IV adverse events: 1 diaphragmatic perforation, 1 liver abscess, and 1 biloma. Pneumothorax was associated with location adjacent to the diaphragm (P < .001) and transpulmonary approach (P < .001). Median length of hospital stay was 2 days (interquartile range [IQR], 1-3 days) for patients who needed thoracostomy (n = 20, 9.6%) compared with 1 day (IQR, 1-8 days) for those who did not, without long-term sequelae.

CONCLUSIONS

MWA of CLM adjacent to the diaphragm is effective and safe, without difference in success and 12-month LTPFS. Pneumothorax was associated with location adjacent to the diaphragm and thoracostomy that resulted in longer hospitalization without long-term sequelae.

Contribution and advances of robotics in percutaneous oncological interventional radiology

The advent of robotic systems in interventional radiology marks a significant evolution in minimally invasive medical procedures, offering enhanced precision, safety, and efficiency. This review comprehensively analyzes the current state and applications of robotic system usage in interventional radiology, which can be particularly helpful for complex procedures and in challenging anatomical regions. Robotic systems can improve the accuracy of interventions like microwave ablation, radiofrequency ablation, and irreversible electroporation. Indeed, studies have shown a notable decrease of an average 30% in the mean deviation of probes, and a 40% lesser need for adjustments during interventions carried out with robotic assistance. Moreover, this review highlights a 35% reduction in radiation dose and a stable-to-30% reduction in operating time associated with robot-assisted procedures compared to manual methods. Additionally, the potential of robotic systems to standardize procedures and minimize complications is discussed, along with the challenges they pose, such as setup duration, organ movement, and a lack of tactile feedback. Despite these advancements, the field still grapples with a dearth of randomized controlled trials, which underscores the need for more robust evidence to validate the efficacy and safety of robotic system usage in interventional radiology.

Ablative margin quantification using deformable versus rigid image registration in colorectal liver metastasis thermal ablation: a retrospective single-center study

PURPOSE

To investigate the correlation of minimal ablative margin (MAM) quantification using biomechanical deformable (DIR) versus intensity-based rigid image registration (RIR) with local outcomes following colorectal liver metastasis (CLM) thermal ablation.

METHODS

This retrospective single-institution study included consecutive patients undergoing thermal ablation between May 2016 and October 2021. Patients who did not have intraprocedural pre- and post-ablation contrast-enhanced CT images for MAM quantification or follow-up period less than 1 year without residual tumor or local tumor progression (LTP) were excluded. DIR and RIR methods were used to quantify the MAM. The registration accuracy was compared using Dice similarity coefficient (DSC). Area under the receiver operating characteristic curve (AUC) was used to test MAM in predicting local tumor outcomes.

RESULTS

A total of 72 patients (mean age 57; 44 men) with 139 tumors (mean diameter 1.5 cm ± 0.8 (SD)) were included. During a median follow-up of 29.4 months, there was one residual unablated tumor and the LTP rate was 17% (24/138). The ranges of DSC were 0.96-0.98 and 0.67-0.98 for DIR and RIR, respectively (p < 0.001). When using DIR, 27 (19%) tumors were partially or totally registered outside the liver, compared to 46 (33%) with RIR. Using DIR versus RIR, the corresponding median MAM was 4.7 mm versus 4.0 mm, respectively (p = 0.5). The AUC in predicting residual tumor and 1-year LTP for DIR versus RIR was 0.89 versus 0.72, respectively (p < 0.001).

CONCLUSION

Ablative margin quantified on intra-procedural CT imaging using DIR method outperformed RIR for predicting local outcomes of CLM thermal ablation.

CLINICAL RELEVANCE STATEMENT

The study supports the role of biomechanical deformable image registration as the preferred image registration method over rigid image registration for quantifying minimal ablative margins using intraprocedural contrast-enhanced CT images.

KEY POINTS

• Accurate and reproducible image registration is a prerequisite for clinical application of image-based ablation confirmation methods. • When compared to intensity-based rigid image registration, biomechanical deformable image registration for minimal ablative margin quantification was more accurate for liver registration using intraprocedural contrast-enhanced CT images. • Biomechanical deformable image registration outperformed intensity-based rigid image registration for predicting local tumor outcomes following colorectal liver metastasis thermal ablation.

Single-arm prospective study comparing ablation zone volume between time zero and 24 h after microwave ablation of liver tumors

PURPOSE

Percutaneous thermal ablation is an effective treatment for primary and metastatic liver tumors and is a recommended local therapy for early-stage hepatocellular carcinoma (HCC). Reported evidence shows an increase in the ablation zone volume over the first 24-h post-liver ablation. This report compares ablation zone volumes immediately at the completion (T = 0) of 26 microwave ablations of liver tumors to 24-h post-procedure (T = 24) volumes.

MATERIALS AND METHODS

20 patients, 13 (65%) males, underwent a total of 26 hepatic microwave ablations (MWA) under ultrasound guidance. Contrast-enhanced CT (CECT) or MRI was performed immediately and another CECT 24 h post operatively. Evaluation of the ablation zone and comparison of the two post-operative scans were done using BioTrace software. The expansion of ablation zones on post-op CECTs was matched point by point per direction. The distance between each 2 points was measured and grouped by distance. The incidence of each specific distance was then converted into a percentage, first for each case separately, then for all cases altogether. Data were tested by a matched paired one-sided t test.

RESULTS

The median lesion diameter was 1.5 cm (range 0.5-3.3) with 16 (62%) HCC cases and 9 hepatic metastases (4 neuroendocrine carcinoma, 4 colorectal carcinomas, 1 breast carcinoma, 1 pancreatic cancer). The data show a consistent volume expansion greater than 30% (p = 7.7e-5) 24-h post-ablation, where the median expansion is 57%. Distances between T = 0 and T = 24 equal to 3-7 mm occur in over 35% of the cases.

CONCLUSION

The ablation zone expansion at 24-h post-op was not uniform. The final ablation zone is difficult to predict at the time of the procedure. The awareness of the ablation zone expansion is important when treating near-critical structures, managing the heat sink effect, and preserving liver parenchyma.

Identification of A0 minimum ablative margins for colorectal liver metastases: multicentre, retrospective study using deformable CT registration and artificial intelligence-based autosegmentation

BACKGROUND

Several ablation confirmation software methods for minimum ablative margin assessment have recently been developed to improve local outcomes for patients undergoing thermal ablation of colorectal liver metastases. Previous assessments were limited to single institutions mostly at the place of development. The aim of this study was to validate the previously identified 5 mm minimum ablative margin (A0) using autosegmentation and biomechanical deformable image registration in a multi-institutional setting.

METHODS

This was a multicentre, retrospective study including patients with colorectal liver metastases undergoing CT- or ultrasound-guided microwave or radiofrequency ablation during 2009-2022, reporting 3-year local disease progression (residual unablated tumour or local tumour progression) rates by minimum ablative margin across all institutions and identifying an intraprocedural contrast-enhanced CT-based minimum ablative margin associated with a 3-year local disease progression rate of less than 1%.

RESULTS

A total of 400 ablated colorectal liver metastases (median diameter of 1.5 cm) in 243 patients (145 men; median age of 62 [interquartile range 54-70] years) were evaluated, with a median follow-up of 26 (interquartile range 17-40) months. A total of 119 (48.9%) patients with 186 (46.5%) colorectal liver metastases were from international institutions B, C, and D that were not involved in the software development. Three-year local disease progression rates for 0 mm, >0 and <5 mm, and 5 mm or larger minimum ablative margins were 79%, 15%, and 0% respectively for institution A (where the software was developed) and 34%, 19%, and 2% respectively for institutions B, C, and D combined. Local disease progression risk decreased to less than 1% with an intraprocedurally confirmed minimum ablative margin greater than 4.6 mm.

CONCLUSION

A minimum ablative margin of 5 mm or larger demonstrates optimal local oncological outcomes. It is proposed that an intraprocedural minimum ablative margin of 5 mm or larger, confirmed using biomechanical deformable image registration, serves as the A0 for colorectal liver metastasis thermal ablation.

Interventional Oncology: 2024 Update

Interventional Oncology (IO) stands at the forefront of transformative cancer care, leveraging advanced imaging technologies and innovative interventions. This narrative review explores recent developments within IO, highlighting its potential impact facilitated by artificial intelligence (AI), personalized medicine and imaging innovations. The integration of AI in IO holds promise for accelerating tumour detection and characterization, guiding treatment strategies and refining predictive models. Imaging modalities, including functional MRI, PET and cone beam CT are reshaping imaging and precision. Navigation, fusion imaging, augmented reality and robotics have the potential to revolutionize procedural guidance and offer unparalleled accuracy. New developments are observed in embolization and ablative therapies. The pivotal role of genomics in treatment planning, targeted therapies and biomarkers for treatment response prediction underscore the personalization of IO. Quality of life assessment, minimizing side effects and long-term survivorship care emphasize patient-centred outcomes after IO treatment. The evolving landscape of IO training programs, simulation technologies and workforce competence ensures the field's adaptability. Despite barriers to adoption, synergy between interventional radiologists' proficiency and technological advancements hold promise in cancer care.

Multimodality quantitative ultrasound envelope statistics imaging based support vector machines for characterizing tissue scatterer distribution patterns: Methods and application in detecting microwave-induced thermal lesions

Ultrasound envelope statistics imaging, including ultrasound Nakagami imaging, homodyned-K imaging, and information entropy imaging, is an important group of quantitative ultrasound techniques for characterizing tissue scatterer distribution patterns, such as scatterer concentrations and arrangements. In this study, we proposed a machine learning approach to integrate the strength of multimodality quantitative ultrasound envelope statistics imaging techniques and applied it to detecting microwave ablation induced thermal lesions in porcine liver ex vivo. The quantitative ultrasound parameters included were homodyned-K α which is a scatterer clustering parameter related to the effective scatterer number per resolution cell, Nakagami m which is a shape parameter of the envelope probability density function, and Shannon entropy which is a measure of signal uncertainty or complexity. Specifically, the homodyned-K log10(α), Nakagami-m, and horizontally normalized Shannon entropy parameters were combined as input features to train a support vector machine (SVM) model to classify thermal lesions with higher scatterer concentrations from normal tissues with lower scatterer concentrations. Through heterogeneous phantom simulations based on Field II, the proposed SVM model showed a classification accuracy above 0.90; the area accuracy and Dice score of higher-scatterer-concentration zone identification exceeded 83% and 0.86, respectively, with the Hausdorff distance <26. Microwave ablation experiments of porcine liver ex vivo at 60-80 W, 1-3 min showed that the SVM model achieved a classification accuracy of 0.85; compared with single log10(α),m, or hNSE parametric imaging, the SVM model achieved the highest area accuracy (89.1%) and Dice score (0.77) as well as the smallest Hausdorff distance (46.38) of coagulation zone identification. We concluded that the proposed multimodality quantitative ultrasound envelope statistics imaging based SVM approach can enhance the capability to characterize tissue scatterer distribution patterns and has the potential to detect the thermal lesions induced by microwave ablation.

Three-Dimensional Margin as a Predictor of Local Tumor Progression after Microwave Ablation: Intraprocedural versus 4-8-Week Postablation Assessment

PURPOSE

To evaluate the prognostic accuracy of intraprocedural and 4-8-week (current standard) post-microwave ablation zone (AZ) and margin assessments for prediction of local tumor progression (LTP) using 3-dimensional (3D) software.

MATERIALS AND METHODS

Data regarding 100 colorectal liver metastases (CLMs) in 75 patients were collected from 2 prospective fluorodeoxyglucose positron emission tomography (PET)/computed tomography (CT)-guided microwave ablation (MWA) trials. The target CLMs and theoretical 5- and 10-mm margins were segmented and registered intraprocedurally and at 4-8 weeks after MWA contrast-enhanced CT (or magnetic resonance [MR] imaging) using the same methodology and 3D software. Tumor and 5- and 10-mm minimal margin (MM) volumes not covered by the AZ were defined as volumes of insufficient coverage (VICs). The intraprocedural and 4-8-week post-MWA VICs were compared as predictors of LTP using receiver operating characteristic curve analysis.

RESULTS

The median follow-up time was 19.6 months (interquartile range, 7.97-36.5 months). VICs for 5- and 10-mm MMs were predictive of LTP at both time assessments. The highest accuracy for the prediction of LTP was documented with the intra-ablation 5-mm VIC (area under the curve [AUC], 0.78; 95% confidence interval, 0.66-0.89). LTP for a VIC of 6-10-mm margin category was 11.4% compared with 4.3% for >10-mm margin category (P < .001).

CONCLUSIONS

A 3D 5-mm MM is a critical endpoint of thermal ablation, whereas optimal local tumor control is noted with a 10-mm MM. Higher AUCs for prediction of LTP were achieved for intraprocedural evaluation than for the 4-8-week postablation 3D evaluation of the AZ.

Transmission Coefficient-Based Monitoring of Microwave Ablation: Development and Experimental Evaluation in Ex Vivo Tissue

OBJECTIVES

To assess the feasibility of monitoring transient evolution of thermal ablation zones with a microwave transmission coefficient-based technique.

METHODS

Microwave ablation was performed in ex vivo bovine liver with two 2.45 GHz directional antennas. A custom apparatus was developed to enable periodic switching between "heating mode" when power from the generator was coupled to the antennas, and "monitoring mode", when antennas were coupled to a network analyzer for broadband transmission coefficient ( s21) measurements. Experiments were performed with applied powers ranging between 30-50 W per antenna for 53-1219 s. Transient s21 spectra over the course of ablations were analyzed to determine feasibility of predicting extent of ablation zones and compared against ground truth assessment from images of sectioned tissue. A linear regression-based mapping between the two datasets was derived to predict ablation extent.

RESULTS

Normalized average transmission coefficient initially rapidly decreased and then increased before asymptotically approaching steady state, with the transition time ranging between 53 s (45 W) and 109 s (30 W). Analysis of ground truth ablation zone images indicated time to complete ablation of 230-350 s. The relative prediction error for time to complete ablation derived from the s21 data was in the range of 1.6%-2.3% compared to ground truth.

CONCLUSION

We have demonstrated the feasibility of monitoring transient evolution of thermal ablation zones using microwave transmission coefficient measurements in ex vivo tissue.

SIGNIFICANCE

The presented technique has potential to contribute towards addressing the clinical need for a method of monitoring evolution of thermal ablation zones.

Intraprocedural Versus Initial Follow-up Minimal Ablative Margin Assessment After Colorectal Liver Metastasis Thermal Ablation: Which One Better Predicts Local Outcomes?

OBJECTIVES

The aim of this study was to investigate the prognostic value of 3-dimensional minimal ablative margin (MAM) quantified by intraprocedural versus initial follow-up computed tomography (CT) in predicting local tumor progression (LTP) after colorectal liver metastasis (CLM) thermal ablation.

MATERIALS AND METHODS

This single-institution, patient-clustered, tumor-based retrospective study included patients undergoing microwave and radiofrequency ablation between 2016 and 2021. Patients without intraprocedural and initial follow-up contrast-enhanced CT, residual tumors, or with follow-up less than 1 year without LTP were excluded. Minimal ablative margin was quantified by a biomechanical deformable image registration method with segmentations of CLMs on intraprocedural preablation CT and ablation zones on intraprocedural postablation and initial follow-up CT. Prognostic value of MAM to predict LTP was tested using area under the curve and competing-risk regression model.

RESULTS

A total of 68 patients (mean age ± standard deviation, 57 ± 12 years; 43 men) with 133 CLMs were included. During a median follow-up of 30.3 months, LTP rate was 17% (22/133). The median volume of ablation zone was 27 mL and 16 mL segmented on intraprocedural and initial follow-up CT, respectively ( P < 0.001), with corresponding median MAM of 4.7 mm and 0 mm, respectively ( P < 0.001). The area under the curve was higher for MAM quantified on intraprocedural CT (0.89; 95% confidence interval [CI], 0.83-0.94) compared with initial follow-up CT (0.66; 95% CI, 0.54-0.76) in predicting 1-year LTP ( P < 0.001). An MAM of 0 mm on intraprocedural CT was an independent predictor of LTP with a subdistribution hazards ratio of 11.9 (95% CI, 4.9-28.9; P < 0.001), compared with 2.4 (95% CI, 0.9-6.0; P = 0.07) on initial follow-up CT.

CONCLUSIONS

Ablative margin quantified on intraprocedural CT significantly outperformed initial follow-up CT in predicting LTP and should be used for ablation endpoint assessment.

Radiofrequency ablation of hepatocellular carcinoma guided by real-time physics-based ablation simulation: a prospective study

OBJECTIVES

To assess the safety and efficacy of radiofrequency ablation (RFA) guidance software that incorporated patient-specific physics-based simulation of each ablation volume.

MATERIALS AND METHODS

Patients referred for curative ablation of hepatocellular carcinoma (HCC) of 2-5 cm diameter were prospectively enrolled. RFA was performed under general anesthesia. Procedure planning and intraprocedural modifications were guided by computer simulation of each ablation. The segmented target (tumor with 5 mm margin) was registered to and superimposed on subsequent 3D multiplanar images. The applied RF energy was used to calculate a simulated ablation volume which was displayed relative to the electrode and segmented target, to depict any untreated target tissue. After each additional ablation, the software updated the accumulated simulated ablation volume in relation to the target. The primary endpoints were technical efficacy and rate of local tumor progression (LTP).

RESULTS

Sixty-eight tumors were ablated during 57 procedures in 52 patients (68.3 ± 9.2 years old, 78.8% male); 15 (26.3%) had multiple lesions and 23 (39.1%) had prior HCC treatment. The mean tumor diameter was 2.73 (±0.64) cm. The intraprocedural simulation directed additional overlapping ablations in 75.9% of tumors. Technical success and efficacy were 100% at 3-month contrast enhanced CT or MRI follow-up after the single treatment session. Cumulative incidence function estimates for 1- and 2-year LTP were 3.9% and 20.2%, respectively.

CONCLUSION

This prospective study found computer-assisted guidance that simulated each ablation was both safe and efficacious. The low rate of LTP was similar to studies that employed stereotactic guidance and ablation confirmation, without requiring a second contrast enhanced study.

MRI non-rigid registration with tumor contraction correction for ablative margin assessment after microwave ablation of hepatocellular carcinomas

Objective. This study aims to develop and assess a tumor contraction model, enhancing the precision of ablative margin (AM) evaluation after microwave ablation (MWA) treatment for hepatocellular carcinomas (HCCs).Approach. We utilize a probabilistic method called the coherent point drift algorithm to align pre-and post-ablation MRI images. Subsequently, a nonlinear regression method quantifies local tumor contraction induced by MWA, utilizing data from 47 HCC with viable ablated tumors in post-ablation MRI. After automatic non-rigid registration, correction for tumor contraction involves contracting the 3D contour of the warped tumor towards its center in all orientations.Main results. We evaluate the performance of our proposed method on 30 HCC patients who underwent MWA. The Dice similarity coefficient between the post-ablation liver and the warped pre-ablation livers is found to be 0.95 ± 0.01, with a mean corresponding distance between the corresponding landmarks measured at 3.25 ± 0.62 mm. Additionally, we conduct a comparative analysis of clinical outcomes assessed through MRI over a 3 month follow-up period, noting that the AM, as evaluated by our proposed method, accurately detects residual tumor after MWA.Significance. Our proposed method showcases a high level of accuracy in MRI liver registration and AM assessment following ablation treatment. It introduces a potentially approach for predicting incomplete ablations and gauging treatment success.

Physio-chemical Modifications to Re-engineer Small Extracellular Vesicles for Targeted Anticancer Therapeutics Delivery and Imaging

Cancer theranostics developed through nanoengineering applications are essential for targeted oncologic interventions in the new era of personalized and precision medicine. Recently, small extracellular vesicles (sEVs) have emerged as an attractive nanoengineering platform for tumor-directed anticancer therapeutic delivery and imaging of malignant tumors. These natural nanoparticles have multiple advantages over synthetic nanoparticle-based delivery systems, such as intrinsic targeting ability, less immunogenicity, and a prolonged circulation time. Since the inception of sEVs as a viable replacement for liposomes (synthetic nanoparticles) as a drug delivery vehicle, many studies have attempted to further the therapeutic efficacy of sEVs. This article discusses engineering strategies for sEVs using physical and chemical methods to enhance their anticancer therapeutic delivery performance. We review physio-chemical techniques of effective therapeutic loading into sEV, sEV surface engineering for targeted entry of therapeutics, and its cancer environment sensitive release inside the cells/organ. Next, we also discuss the novel hybrid sEV systems developed by a combination of sEVs with lipid and metal nanoparticles to garner each component's benefits while overcoming their drawbacks. The article extensively analyzes multiple sEV labeling techniques developed and investigated for live tracking or imaging sEVs. Finally, we discuss the theranostic potential of engineered sEVs in future cancer care regimens.

3D fusion is superior to 2D point-to-point contrast-enhanced US to evaluate the ablative margin after RFA for hepatocellular carcinoma

PURPOSE

To compare the efficiency of three-dimensional (3D) and two-dimensional (2D) contrast-enhanced ultrasound (CEUS)-derived techniques in evaluating the ablative margin (AM) after radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC).

METHODS

In total, 98 patients with 98 HCCs were enrolled. The 2D CEUS point-to-point imaging (2D CEUS-PI) was conducted by comparing the pre- and post-RFA 2D CEUS images manually, and the 3D CEUS fusion imaging (3D CEUS-FI) was conducted by fusing the pre- and post-RFA 3D CEUS images automatically. These two techniques were compared in distinguishing an adequate AM ≥ 5 mm. Risk factors for local tumor progression (LTP) after RFA were analyzed by the Kaplan-Meier method with log-rank test.

RESULTS

The mean registration time of 3D CEUS-FI and 2D CEUS-PI was 5.0 and 9.3 min, respectively (p < 0.0001). The kappa coefficient was 0.680 for agreement between 2D CEUS-PI and 3D CEUS-FI in the evaluation of AM (p < 0.0001). Tumors with AM < 5 mm by 2D CEUS-PI were all identified as AM < 5 mm by 3D CEUS-FI. Nonetheless, 16 (26%) tumors identified as AM ≥ 5 mm by 2D CEUS-PI were re-classified as AM < 5 mm by 3D CEUS-FI. During a median follow-up time of 31.2 months (range, 3.2-66.0 months), LTP was identified in 8 tumors. The estimated 1-/2-/3-year cumulative incidence of LTP was 4.4%, 8.1%, and 10.3%, respectively. Higher estimated cumulative incidence of LTP was identified in tumors with AM < 5 mm by 2D CEUS-PI (at 3-year, 27.2% vs 0%; p < 0.001), and by 3D CEUS-FI (at 3-year, 20.7% vs 0%; p = 0.004).

CONCLUSION

3D CEUS-FI excelled in the evaluation of AM when compared with 2D CEUS-PI. With equivalent efficacy in the prediction of LTP, 3D CEUS-FI was superior to 2D CEUS-PI for its automatic and time-saving procedure.

CLINICAL RELEVANCE STATEMENT

3D CEUS fusion imaging may serve as an effective tool in evaluating ablative margin and predicting local tumor progression after RFA in HCC.

KEY POINTS

• Both 2D and 3D CEUS-derived techniques could evaluate ablative margin (AM) after RFA for hepatocellular carcinoma. • 3D CEUS fusion imaging was more precise in the evaluation of AM compared to 2D CEUS point-to-point imaging, with advantages of its automatic and time-saving procedure. • An inadequate AM < 5 mm evaluated by CEUS-derived techniques was the only risk factor of LTP after RFA for hepatocellular carcinoma (p < 0.001 for 2D CEUS point-to-point imaging, and p = 0.004 for 3D CEUS fusion imaging).

The Importance of Optimal Thermal Ablation Margins in Colorectal Liver Metastases: A Systematic Review and Meta-Analysis of 21 Studies

BACKGROUND

Colorectal cancer (CRC) is the second most common cause of cancer-related deaths in the US. Thermal ablation (TA) can be a comparable alternative to partial hepatectomy for selected cases when eradication of all visible tumor with an ablative margin of greater than 5 mm is achieved. This systematic review and meta-analysis aimed to encapsulate the current clinical evidence concerning the optimal TA margin for local cure in patients with colorectal liver metastases (CLM).

METHODS

MEDLINE, EMBASE, and the CENTRAL databases were systematically searched from inception until 1 May 2023, in accordance with the PRISMA Guidelines. Measure of effect included the risk ratio (RR) with 95% confidence interval (CI) using the random-effects model.

RESULTS

Overall, 21 studies were included, comprising 2005 participants and 2873 ablated CLMs. TA with margins less than 5 mm were associated with a 3.6 times higher risk for LTP (n = 21 studies, RR: 3.60; 95% CI: 2.58-5.03; p-value < 0.001). When margins less than 5 mm were additionally confirmed by using 3D software, a 5.1 times higher risk for LTP (n = 4 studies, RR: 5.10; 95% CI: 1.45-17.90; p-value < 0.001) was recorded. Moreover, a thermal ablation margin of less than 10 mm but over 5 mm remained significantly associated with 3.64 times higher risk for LTP vs. minimal margin larger than 10 mm (n = 7 studies, RR: 3.64; 95% CI: 1.31-10.10; p-value < 0.001).

CONCLUSIONS

This meta-analysis solidifies that a minimal ablation margin over 5 mm is the minimum critical endpoint required, whereas a minimal margin of at least 10 mm yields optimal local tumor control after TA of CLMs.

Ablation margin quantification after thermal ablation of malignant liver tumors: How to optimize the procedure? A systematic review of the available evidence

Introduction

To minimize the risk of local tumor progression after thermal ablation of liver malignancies, complete tumor ablation with sufficient ablation margins is a prerequisite. This has resulted in ablation margin quantification to become a rapidly evolving field. The aim of this systematic review is to give an overview of the available literature with respect to clinical studies and technical aspects potentially influencing the interpretation and evaluation of ablation margins.

Methods

The Medline database was reviewed for studies on radiofrequency and microwave ablation of liver cancer, ablation margins, image processing and tissue shrinkage. Studies included in this systematic review were analyzed for qualitative and quantitative assessment methods of ablation margins, segmentation and co-registration methods, and the potential influence of tissue shrinkage occurring during thermal ablation.

Results

75 articles were included of which 58 were clinical studies. In most clinical studies the aimed minimal ablation margin (MAM) was ≥ 5 mm. In 10/31 studies, MAM quantification was performed in 3D rather than in three orthogonal image planes. Segmentations were performed either semi-automatically or manually. Rigid and non-rigid co-registration algorithms were used about as often. Tissue shrinkage rates ranged from 7% to 74%.

Conclusions

There is a high variability in ablation margin quantification methods. Prospectively obtained data and a validated robust workflow are needed to better understand the clinical value. Interpretation of quantified ablation margins may be influenced by tissue shrinkage, as this may cause underestimation.

Percutaneous image-guided ablation for hepatic metastases

The presence of hepatic metastases indicates advanced disease and is associated with significant morbidity and mortality, especially when the hepatic disease is not amenable to locoregional treatments. The primary tumour of origin, the distribution and extent of metastatic disease, the underlying liver reserve, the patient performance status and the presence of comorbidities are factors that determine whether a patient will benefit from hepatectomy or local curative-intent treatments. For patients with metastatic colorectal cancer, the most common primary cancer that spreads to the liver, several studies have demonstrated a survival benefit for patients who can be treated with hepatectomy and/or percutaneous ablation, compared to those treated with chemotherapy alone. Despite advances in surgical techniques increasing the percentage of patients eligible for surgery, most patients have unresectable disease or are poor surgical candidates. Percutaneous ablation can be used to provide local disease control and prolong survival for both surgical and non-surgical candidates. This is typically offered to patients with small hepatic metastases that can be ablated with optimal (≥10 mm) or at least adequate minimum ablation margins (≥5 mm), as high local tumour control rates can be achieved for these patients which are comparable to surgical resection. This review summarizes available evidence and outcomes following percutaneous ablation of the most frequently encountered types of hepatic metastases in the clinical practice of interventional oncology. Patient selection, technical considerations, follow-up protocols and oncologic outcomes are presented and discussed.

Study Protocol STEREOLAB: Stereotactic Liver Ablation Assisted with Intra-Arterial CT Hepatic Arteriography and Ablation Confirmation Software Assessment

PURPOSE

This study aims to evaluate the technical efficacy and local tumor progression-free survival (LTPFS) of a standardized workflow for thermal ablation of colorectal liver metastases (CRLM) consisting of CT during hepatic arteriography (CTHA)-based imaging analysis, stereotactic thermal ablation, and computer-based software assessment of ablation margins.

MATERIALS AND METHODS

This investigator initiated, single-center, single-arm prospective trial will enroll up to 50 patients (≤ 5 CRLM, Measuring ≤ 5 cm). Procedures will be performed in an angio-CT suite under general anesthesia. The primary objective is to estimate LTPFS with a follow-up of up to 2 years and secondary objectives are analysis of the impact of minimal ablative margins on LTPFS, adverse events, contrast media utilization and radiation exposure, overall oncological outcomes, and anesthesia/procedural time. Adverse events (AE) will be recorded by CTCAE (Common Toxicity Criteria for Adverse Events), and Bayesian optimal phase-2 design will be applied for major intraprocedural AE stop boundaries. The institutional CRLM ablation registry will be used as benchmark for comparative analysis with the historical cohort.

DISCUSSION

The STEREOLAB trial will introduce a high-precision and standardized thermal ablation workflow for CRLM consisting of CT during hepatic arteriography imaging, stereotactic guidance, and ablation confirmation. Trial Registration ClinicalTrials.gov identifier: (NCT05361551).

Thermal ablation with configurable shapes: a comprehensive, automated model for bespoke tumor treatment

BACKGROUND

Malignant tumors routinely present with irregular shapes and complex configurations. The lack of customization to individual tumor shapes and standardization of procedures limits the success and application of thermal ablation.

METHODS

We introduced an automated treatment model consisting of (i) trajectory and ablation profile planning, (ii) ablation probe insertion, (iii) dynamic energy delivery (including robotically driven control of the energy source power and location over time, according to a treatment plan bespoke to the tumor shape), and (iv) quantitative ablation margin verification. We used a microwave ablation system and a liver phantom (acrylamide polymer with a thermochromic ink) to mimic coagulation and measure the ablation volume. We estimated the ablation width as a function of power and velocity following a probabilistic model. Four representative shapes of liver tumors < 5 cm were selected from two publicly available databases. The ablated specimens were cut along the ablation probe axis and photographed. The shape of the ablated volume was extracted using a color-based segmentation method.

RESULTS

The uncertainty (standard deviation) of the ablation width increased with increasing power by ± 0.03 mm (95% credible interval [0.02, 0.043]) per watt increase in power and by ± 0.85 mm (95% credible interval [0, 2.5]) per mm/s increase in velocity. Continuous ablation along a straight-line trajectory resulted in elongated rotationally symmetric ablation shapes. Simultaneous regulation of the power and/or translation velocity allowed to modulate the ablation width at specific locations.

CONCLUSIONS

This study offers the proof-of-principle of the dynamic energy delivery system using ablation shapes from clinical cases of malignant liver tumors.

RELEVANCE STATEMENT

The proposed automated treatment model could favor the customization and standardization of thermal ablation for complex tumor shapes.

KEY POINTS

• Current thermal ablation systems are limited to ellipsoidal or spherical shapes. • Dynamic energy delivery produces elongated rotationally symmetric ablation shapes with varying widths. • For complex tumor shapes, multiple customized ablation shapes could be combined.

Updated Management of Colorectal Cancer Liver Metastases: Scientific Advances Driving Modern Therapeutic Innovations

Colorectal cancer is the second leading cause of cancer-related deaths in the United States and accounts for an estimated 1 million deaths annually worldwide. The liver is the most common site of metastatic spread from colorectal cancer, significantly driving both morbidity and mortality. Although remarkable advances have been made in recent years in the management for patients with colorectal cancer liver metastases, significant challenges remain in early detection, prevention of progression and recurrence, and in the development of more effective therapeutics. In 2017, our group held a multidisciplinary state-of-the-science symposium to discuss the rapidly evolving clinical and scientific advances in the field of colorectal liver metastases, including novel early detection and prognostic liquid biomarkers, identification of high-risk cohorts, advances in tumor-immune therapy, and different regional and systemic therapeutic strategies. Since that time, there have been scientific discoveries translating into therapeutic innovations addressing the current management challenges. These innovations are currently reshaping the treatment paradigms and spurring further scientific discovery. Herein, we present an updated discussion of both the scientific and clinical advances and future directions in the management of colorectal liver metastases, including adoptive T-cell therapies, novel blood-based biomarkers, and the role of the tumor microbiome. In addition, we provide a comprehensive overview detailing the role of modern multidisciplinary clinical approaches used in the management of patients with colorectal liver metastases, including considerations toward specific molecular tumor profiles identified on next generation sequencing, as well as quality of life implications for these innovative treatments.

Efficacy of Thermal Ablation for Small-Size (0-3 cm) versus Intermediate-Size (3-5 cm) Colorectal Liver Metastases: Results from the Amsterdam Colorectal Liver Met Registry (AmCORE)

PURPOSE

Thermal ablation is widely recognized as the standard of care for small-size unresectable colorectal liver metastases (CRLM). For larger CRLM safety, local control and overall efficacy are not well established and insufficiently validated. The purpose of this comparative series was to analyze outcomes for intermediate-size versus small-size CRLM.

MATERIAL AND METHODS

Patients treated with thermal ablation between December 2000 and November 2021 for small-size and intermediate-size CRLM were included. The primary endpoints were complication rate and local control (LC). Secondary endpoints included local tumor progression-free survival (LTPFS) and overall survival (OS).

RESULTS

In total, 59 patients were included in the intermediate-size (3-5 cm) group and 221 in the small-size (0-3 cm) group. Complications were not significantly different between the two groups (p = 0.546). No significant difference between the groups was found in an overall comparison of OS (HR 1.339; 95% CI 0.824-2.176; p = 0.239). LTPFS (HR 3.388; p < 0.001) and LC (HR 3.744; p = 0.004) were superior in the small-size group. Nevertheless, the 1-, 3-, and 5-year LC for intermediate-size CRLM was still 93.9%, 85.4%, and 81.5%, and technical efficacy improved over time.

CONCLUSIONS

Thermal ablation for intermediate-size unresectable CRLM is safe and induces long-term LC in the vast majority. The results of the COLLISION-XL trial (unresectable colorectal liver metastases: stereotactic body radiotherapy versus microwave ablation-a phase II randomized controlled trial for CRLM 3-5 cm) are required to provide further clarification of the role of local ablative methods for intermediate-size unresectable CRLM.

Multi-Probe RFA vs. Single-Probe MWA in an Ex Vivo Bovine Liver Model: Comparison of Volume and Shape of Coagulation Zones

OBJECTIVES

To compare the volumes and shapes of the coagulation zone (CZ) of a multi-probe RFA system (three RFA electrodes) and a single-probe MWA system from the same vendor in an ex vivo bovine liver model.

MATERIAL & METHODS

A total of 48 CZs were obtained in bovine liver specimens with three different ablation system configurations (single-probe MWA vs. multi-probe RFA with 20 mm inter-probe distance [confluent CZ] vs. multi-probe RFA with 50 mm inter-probe distance [three individual CZs]) at 4, 6, 8, and 10 min ablation time using a fixed ablation protocol. Ablation diameters were measured and ellipticity indices (EIs) and volumes calculated. Calculations for all systems/configurations were compared.

RESULTS

Volumes and diameters increased with ablation time for all configurations. At 4 and 6 min ablation time volumes obtained with the RFA 50 mm setup, and at 8 and 10 min with the RFA 20 mm setup were the largest at 26.5 ± 4.1 mL, 38.1 ± 5.8 mL, 46.3 ± 4.9 mL, 48.4 ± 7.3 mL, respectively. The single-probe MWA could not reach the volumes of the RFA setups for any of the ablation times evaluated. EI were very similar and almost round for RFA 20 mm and single-probe MWA, and differed significantly to the more ovoid ones for the RFA 50 mm configuration.

CONCLUSIONS

The multi-probe RFA system employing three electrodes achieved significantly larger ablation volumes in both configurations (confluent CZ and three individual CZs) per time as compared with a single-probe MWA system in this ex vivo bovine liver model.

Ablative margins in percutaneous thermal ablation of hepatic tumors: a systematic review

INTRODUCTION

This study aims to systematically review current evidence on ablative margins and correlation to local tumor progression (LTP) after thermal ablation of hepatocellular carcinoma (HCC) and colorectal liver metastases (CRLM).

METHODS

A systematic search was performed in PubMed (MEDLINE) and Web of Science to identify all studies that reported on ablative margins (AM) and related LTP rates. Studies were assessed for risk of bias and synthesized separately per tumor type. Where possible, results were pooled to calculate risk differences (RD) as function of AM.

RESULTS

In total, 2910 articles were identified of which 43 articles were eligible for final analysis. There was high variability in AM measurement methodology across studies in terms of measurement technique, imaging modalities, and timing. Most common margin stratification was < 5 mm and > 5 mm, for which data were available in 25/43 studies (58%). Of these, all studies favored AM > 5 mm to reduce the risk of LTP, with absolute RD of 16% points for HCC and 47% points for CRLM as compared to AM < 5 mm.

CONCLUSIONS

Current evidence supports AM > 5 mm to reduce the risk of LTP after thermal ablation of HCC and CRLM. However, standardization of AM measurement and reporting is critical to allow future meta-analyses and improved identification of optimal threshold value for clinical use.

Gradient-based Volumetric PET Parameters on Immediate Pre-ablation FDG-PET Predict Local Tumor Progression in Patients with Colorectal Liver Metastasis Treated by Microwave Ablation

PURPOSE

This study aimed to evaluate the optimal method of segmentation of colorectal liver metastasis (CLM) on immediate pre-ablation PET scans and assess the prognostic value of quantitative pre-ablation PET parameters with regards to local tumor control. A secondary objective was to correlate the target tumor size estimation by PET methods with the tumor measurements on anatomical imaging.

METHODOLOGY

A prospectively accrued cohort of 55 CLMs (46 patients) treated with real-time ¹⁸F-FDG-PET/CT-guided percutaneous microwave ablation was followed-up for a median of 10.8 months (interquartile: 5.5-20.2). Total lesion glycolysis (TLG) and metabolic tumor volume (MTV) values of each CLM were derived from pre-ablation ¹⁸F-FDG-PET with gradient and threshold PET segmentation methodologies. The event was defined as local tumor progression (LTP). Time-dependent receiver operating characteristic (ROC) curve analyses were used to assess area under the curves (AUCs). Intraclass correlation (ICC) and 95.0% confidence interval (CI) were performed to measure the linear relationships between the continuous variables.

RESULTS

AUCs for prediction of LTP obtained from time-dependent ROC analysis for the gradient technique were higher in comparison to the threshold methodologies (AUCs for TLG and volume were: 0.790 and 0.807, respectively). ICC between PET gradient-based and anatomical measurements were higher in comparison to threshold methodologies (ICC for the longest diameter: 733 (95.0% CI 0.538-0.846), ICC for the shortest diameter: .747 (95.0% CI 0.546-0.859), p-values < 0.001).

CONCLUSIONS

The gradient-based technique had a higher AUC for prediction of LTP after microwave ablation of CLM and showed the highest correlation with anatomical imaging tumor measurements.

Efficacy of fusion imaging for immediate post-ablation assessment of malignant liver neoplasms: A systematic review

BACKGROUND

Percutaneous thermal ablation has become the preferred therapeutic treatment option for liver cancers that cannot be resected. Since ablative zone tissue changes over time, it becomes challenging to determine therapy effectiveness over an extended period. Thus, an immediate post-procedural evaluation of the ablation zone is crucial, as it could influence the need for a second-look treatment or follow-up plan. Assessing treatment response immediately after ablation is essential to attain favorable outcomes. This study examines the efficacy of image fusion strategies immediately post-ablation in liver neoplasms to determine therapeutic response.

METHODOLOGY

A comprehensive systematic search using PRISMA methodology was conducted using EMBASE, MEDLINE (via PUBMED), and Cochrane Library Central Registry electronic databases to identify articles that assessed the immediate post-ablation response in malignant hepatic tumors with fusion imaging (FI) systems. The data were retrieved on relevant clinical characteristics, including population demographics, pre-intervention clinical history, lesion characteristics, and intervention type. For the outcome metrics, variables such as average fusion time, intervention metrics, technical success rate, ablative safety margin, supplementary ablation rate, technical efficacy rate, LTP rates, and reported complications were extracted.

RESULTS

Twenty-two studies were included for review after fulfilling the study eligibility criteria. FI's immediate technical success rate ranged from 81.3% to 100% in 17/22 studies. In 16/22 studies, the ablative safety margin was assessed immediately after ablation. Supplementary ablation was performed in 9 studies following immediate evaluation by FI. In 15/22 studies, the technical effectiveness rates during the first follow-up varied from 89.3% to 100%.

CONCLUSION

Based on the studies included, we found that FI can accurately determine the immediate therapeutic response in liver cancer ablation image fusion and could be a feasible intraprocedural tool for determining short-term post-ablation outcomes in unresectable liver neoplasms. There are some technical challenges that limit the widespread adoption of FI techniques. Large-scale randomized trials are warranted to improve on existing protocols. Future research should emphasize improving FI's technological capabilities and clinical applicability to a broader range of tumor types and ablation procedures.

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

Background Confirming ablation completeness with sufficient ablative margin is critical for local tumor control following colorectal liver metastasis (CLM) ablation. An image-based confirmation method considering patient- and ablation-related biomechanical deformation is an unmet need. Purpose To evaluate a biomechanical deformable image registration (DIR) method for three-dimensional (3D) minimal ablative margin (MAM) quantification and the association with local disease progression following CT-guided CLM ablation. Materials and Methods This single-institution retrospective study included patients with CLM treated with CT-guided microwave or radiofrequency ablation from October 2015 to March 2020. A biomechanical DIR method with AI-based autosegmentation of liver, tumors, and ablation zones on CT images was applied for MAM quantification retrospectively. The per-tumor incidence of local disease progression was defined as residual tumor or local tumor progression. Factors associated with local disease progression were evaluated using the multivariable Fine-Gray subdistribution hazard model. Local disease progression sites were spatially localized with the tissue at risk for tumor progression (<5 mm) using a 3D ray-tracing method. Results Overall, 213 ablated CLMs (mean diameter, 1.4 cm) in 124 consecutive patients (mean age, 57 years ± 12 [SD]; 69 women) were evaluated, with a median follow-up interval of 25.8 months. In ablated CLMs, an MAM of 0 mm was depicted in 14.6% (31 of 213), from greater than 0 to less than 5 mm in 40.4% (86 of 213), and greater than or equal to 5 mm in 45.1% (96 of 213). The 2-year cumulative incidence of local disease progression was 72% for 0 mm and 12% for greater than 0 to less than 5 mm. No local disease progression was observed for an MAM greater than or equal to 5 mm. Among 117 tumors with an MAM less than 5 mm, 36 had local disease progression and 30 were spatially localized within the tissue at risk for tumor progression. On multivariable analysis, an MAM of 0 mm (subdistribution hazard ratio, 23.3; 95% CI: 10.8, 50.5; P < .001) was independently associated with local disease progression. Conclusion Biomechanical deformable image registration and autosegmentation on CT images enabled identification and spatial localization of colorectal liver metastases at risk for local disease progression following ablation, with a minimal ablative margin greater than or equal to 5 mm as the optimal end point. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Sofocleous in this issue.

Colorectal Cancer Liver Metastases: Genomics and Biomarkers with Focus on Local Therapies

Molecular cancer biomarkers help personalize treatment, predict oncologic outcomes, and identify patients who can benefit from specific targeted therapies. Colorectal cancer (CRC) is the third-most common cancer, with the liver being the most frequent visceral metastatic site. KRAS, NRAS, BRAF V600E Mutations, DNA Mismatch Repair Deficiency/Microsatellite Instability Status, HER2 Amplification, and NTRK Fusions are NCCN approved and actionable molecular biomarkers for colorectal cancer. Additional biomarkers are also described and can be helpful in different image-guided hepatic directed therapies specifically for CRLM. For example, tumors maintaining the Ki-67 proliferation marker after thermal ablation was shown to be particularly resilient to ablation. Ablation margin was also shown to be an important factor in predicting local recurrence, with a ≥10 mm minimal ablation margin being required to attain local tumor control, especially for patients with mutant KRAS CRLM.

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

PURPOSE

The aim of this study was to compare the effectiveness and outcomes of percutaneous ablation guided by ultrasonography (US) and computed tomography (CT) in colorectal liver oligometastases (CLOM).

METHODS

This study included patients with CLOM treated with percutaneous ablation from January 2008 to January 2021 in this observational study. Only lesions visualized on both CT and US images were further analyzed according to whether patients' initial ablation treatments utilized US guidance or CT guidance. The Kaplan-Meier method was used to estimate local tumor progression (LTP)-free survival after propensity score matching (PSM). The LTP-free survival and treatment-related outcomes were compared between these two groups.

RESULTS

PSM identified 116 patients from each group, with 269 and 238 lesions in the USguided and CT-guided groups, respectively. US-guided ablation had a shorter average procedure time and lower cost than CT-guided ablation (27.54±12.06 minutes vs. 32.70±13.88 minutes, P=0.003; $2,175.13±618.17 vs. $2,455.49±710.25, P=0.002). For patients >60 years of age, the cumulative LTP rate at 1 year was lower in the US-guided group than in the CT-guided group (17.8% vs. 25.1%, P=0.038). For patients with perivascular liver lesions, the cumulative LTP rate at 1 year was lower in the US-guided group (14.4% vs. 28.2%, P=0.040).

CONCLUSION

For patients whose age is >60 years or who have perivascular liver lesions, USguided ablation is better than CT-guided ablation, with a shorter treatment time and lower costs when both ablation methods are feasible for patients.

Real-Time Split-Dose PET/CT-Guided Ablation Improves Colorectal Liver Metastasis Detection and Ablation Zone Margin Assessments without the Need for Repeated Contrast Injection

BACKGROUND

Real-time split-dose PET can identify the targeted colorectal liver metastasis (CLM) and eliminate the need for repeated contrast administration before and during thermal ablation (TA). This study aimed to assess the added value of pre-ablation real-time split-dose PET when combined with non-contract CT in the detection of CLM for ablation and the evaluation of the ablation zone and margins.

METHODS

A total of 190 CLMs/125 participants from two IRB-approved prospective clinical trials using PET/CT-guided TA were analyzed. Based on detection on pre-TA imaging, CLMs were categorized as detectable, non-detectable, and of poor conspicuity on CT alone, and detectable, non-detectable, and low FDG-avidity on PET/CT after the initial dose. Ablation margins around the targeted CLM were evaluated using a 3D volumetric approach.

RESULTS

We found that 129/190 (67.9%) CLMs were detectable on CT alone, and 61/190 CLMs (32.1%) were undetectable or of poor conspicuity, not allowing accurate depiction and targeting by CT alone. Thus, the theoretical 5- and 10-mm margins could not be defined in these tumors (32.1%) using CT alone. When TA intraprocedural PET/CT images are obtained and inspected (fused PET/CT), only 4 CLM (2.1%) remained undetectable or had a low FDG avidity.

CONCLUSIONS

The addition of PET to non-contrast CT improved CLM detection for ablation targeting, margin assessments, and continuous depiction of the FDG avid CLMs during the ablation without the need for multiple intravenous contrast injections pre- and intra-procedurally.

Comparison of Two 2.45 GHz Microwave Ablation Devices with Respect to Ablation Zone Volume in Relation to Applied Energy in Patients with Malignant Liver Tumours

Purpose: (i) to compare two 2.45 GHz MWA devices with respect to AZV in relation to the applied energy after MWA in patients with hepatocellular carcinoma (HCC) or colorectal liver metastasis (CRLM) and (ii) to identify potential confounders for this relationship. Methods: In total, 102 tumours, 65 CRLM and 37 HCC were included in this retrospective analysis. Tumours were treated with Emprint (n = 71) or Neuwave (n = 31) MWA devices. Ablation treatment setting were recorded and applied energy was calculated. AZV and tumour volumes were segmented on the contrast-enhanced CT scans obtained 1 week after treatment. The AZV to applied energy R(AZV:E) ratios were calculated for each tumour treatment and compared between both MWA devices and tumour types. Results: R(AZV:E)EMPRINT was 0.41 and R(AZV:E)NEUWAVE was 0.81, p < 0.001. Moderate correlation between AZV and applied energy was found for Emprint (r = 0.57, R2 = 0.32, p < 0.001) and strong correlation was found for Neuwave (r = 0.78, R2 = 0.61, p < 0.001). R(AZV:E)CRLM was 0.45 and R(AZV:E)HCC was 0.52, p = 0.270. Conclusion: This study confirms the unpredictability of AZVs based on the applied output energy for HCC and CRLM. No significant differences in R(AZV:E) were observed between CRLM and HCC. Significantly lower R(AZV:E) was found for Emprint devices compared to Neuwave; however, reflected energy due to cable and antenna design remains unclear and might contribute to these differences.

Three-dimensional quantitative margin assessment in patients with colorectal liver metastases treated with percutaneous thermal ablation using semi-automatic rigid MRI/CECT-CECT co-registration

PURPOSE

To assess the quantitative minimal ablation margin (MAM) in patients with colorectal liver metastases (CRLM) treated with percutaneous thermal ablation (TA) and correlate the quantitative MAM with local tumour recurrence (LTR).

METHOD

Thirty-nine of 143 patients with solitary or multiple CRLM who underwent a first percutaneous TA procedure between January 2011 and May 2020 were considered eligible for study enrolment. Image fusion of pre- and post-ablation scans and 3D quantitative MAM assessment was performed using the in-house developed semi-automatic rigid MRI/CECT-CECT co-registration software deLIVERed. The quantitative MAM was analysed and correlated with LTR.

RESULTS

Eighteen (46 %) patients were additionally excluded from further analyses due to suboptimal co-registration (quality co-registration score ≤ 3). The quality of co-registration was considered sufficient in 21 (54 %) patients with a total of 29 CRLM. LTR was found in 5 of 29 (17 %) TA-treated CRLM. In total, 12 (41 %) negative MAMs were measured (mean MAM -4.7 ± 2.7 mm). Negative MAMs were significantly more frequently seen in patients who developed LTR (100 %) compared to those without LTR (29 %; p = 0.003). The median MAM of patients who developed LTR (-6.6 mm (IQR -9.5 to -4.6)) was significantly smaller compared to the median MAM of patients without LTR (0.5 mm (IQR -1.8 to 3.0); p < 0.001). The ROC curve showed high accuracy in predicting LTR for the quantitative MAM (area under the curve of 0.975 ± 0.029).

CONCLUSION

This study demonstrated the feasibility of 3D quantitative MAM assessment, using deLIVERed co-registration software, to assess technical success of TA in patients with CRLM and to predict LTR.

Local tumour control after radiofrequency or microwave ablation for colorectal liver metastases in relation to histopathological growth patterns

BACKGROUND

Regrowth after ablation is common, but predictive factors for local control are scarce. This study investigates whether histopathological growth patterns (HGP) can be used as a predictive biomarker for local control after ablation of colorectal liver metastases (CRLM).

METHODS

Patients who received simultaneous resection and ablation as first treatment for CRLM between 2000 and 2019 were considered eligible. HGPs were determined on resected CRLM according to international guidelines and were classified as desmoplastic or non-desmoplastic. As minimal inter-tumoural heterogeneity has been demonstrated, the HGP of resected and ablated CRLM were presumed to be identical. Local tumour progression (LTP) was assessed on postoperative surveillance imaging. Uni- and multivariable competing risk methods were used to compare LTP.

RESULTS

In total 221 patients with 443 ablated tumours were analysed. A desmoplastic HGP was found in 60 (27.1%) patients who had a total of 159 (34.7%) ablated lesions. Five-year LTP [95%CI] was significantly higher for ablated CRLM with a presumed non-desmoplastic HGP (37% [30-43] vs 24% [17-32], Gray's-test p = 0.014). On multivariable analysis, a non-desmoplastic HGP (adjusted HR [95%CI]; 1.55 [1.03-2.35]) was independently associated with higher LTP rates after ablation.

CONCLUSION

HGP is an independent predictor of local tumour progression following ablation of CRLM.

Engineered extracellular vesicles as intelligent nanosystems for next-generation nanomedicine

Extracellular vesicles (EVs), as natural carriers of bioactive cargo, have a unique micro/nanostructure, bioactive composition, and characteristic morphology, as well as fascinating physical, chemical and biochemical features, which have shown promising application in the treatment of a wide range of diseases. However, native EVs have limitations such as lack of or inefficient cell targeting, on-demand delivery, and therapeutic feedback. Recently, EVs have been engineered to contain an intelligent core, enabling them to (i) actively target sites of disease, (ii) respond to endogenous and/or exogenous signals, and (iii) provide treatment feedback for optimal function in the host. These advances pave the way for next-generation nanomedicine and offer promise for a revolution in drug delivery. Here, we summarise recent research on intelligent EVs and discuss the use of "intelligent core" based EV systems for the treatment of disease. We provide a critique about the construction and properties of intelligent EVs, and challenges in their commercialization. We compare the therapeutic potential of intelligent EVs to traditional nanomedicine and highlight key advantages for their clinical application. Collectively, this review aims to provide a new insight into the design of next-generation EV-based theranostic platforms for disease treatment.

Long-term outcomes following percutaneous microwave ablation for colorectal cancer liver metastases

PURPOSE

To evaluate the overall survival (OS), local progression-free survival (PFS) and prognostic factors of patients with colorectal cancer liver metastases (CRLM) undergoing microwave ablation (MWA).

METHOD

A total of 132 patients were retrospectively enrolled who had been treated between 2010 and 2018. For the evaluation of survival rates, all patients were divided according to their indications (curative n = 57 and debulking (patients with additional non-target extrahepatic metastases) n = 75). In total, 257 ablations were evaluated for prognostic factors: number of liver metastases, primary tumor origin (PTO), diameter and volume of metastases, duration and energy of ablation.

RESULTS

The OS was 32.1 months with 93.2% of patients free from recurrence at 28.3 months (median follow-up time). The one- year and three-year OS were 82.72% and 41.66%, respectively. The OS and recurrence-free survival of the curative group were statistically significantly higher than the debulking group (p < .001). Statistically significant prognostic factors for OS included the location of the primary tumor (p < .038) and the number of metastases (all p < .017). Metastasis diameter and volume and ablation duration and energy had no significant correlation with survival (p > .05).

CONCLUSIONS

Satisfactory OS and local tumor PFS can be achieved in patients with CRLM using MWA with the number of metastases and the location of the primary tumor influencing the outcome of patients. The metastasis's size and the duration and energy used for ablation were not of significant prognostic value.

Improved Outcomes of Thermal Ablation for Colorectal Liver Metastases: A 10-Year Analysis from the Prospective Amsterdam CORE Registry (AmCORE)

Background

To analyze long-term oncological outcomes of open and percutaneous thermal ablation in the treatment of patients with colorectal liver metastases (CRLM).

Methods

This assessment from a prospective, longitudinal tumor registry included 329 patients who underwent 541 procedures for 1350 CRLM from January 2010 to February 2021. Three cohorts were formed: 2010–2013 (129 procedures [53 percutaneous]), 2014–2017 (206 procedures [121 percutaneous]) and 2018–2021 (206 procedures [135 percutaneous]). Local tumor progression-free survival (LTPFS) and overall survival (OS) data were estimated using the Kaplan–Meier method. Potential confounding factors were analyzed with uni- and multivariable Cox regression analyses.

Results

LTPFS improved significantly over time for percutaneous ablations (2-year LTPFS 37.7% vs. 69.0% vs. 86.3%, respectively, P < .0001), while LTPFS for open ablations remained reasonably stable (2-year LTPFS 87.1% [2010–2013], vs. 92.7% [2014–2017] vs. 90.2% [2018–2021], P = .12). In the latter cohort (2018–2021), the open approach was no longer superior regarding LTPFS (P = .125). No differences between the three cohorts were found regarding OS (P = .088), length of hospital stay (open approach, P = .065; percutaneous approach, P = .054), and rate and severity of complications (P = .404). The rate and severity of complications favored the percutaneous approach in all three cohorts (P = .002).

Conclusion

Over the last 10 years efficacy of percutaneous ablations has improved remarkably for the treatment of CRLM. Oncological outcomes seem to have reached results following open ablation. Given its minimal invasive character and shorter length of hospital stay, whenever feasible, percutaneous procedures may be favored over an open approach.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00270-022-03152-9.