Microwave Ablation for Colorectal Liver Metastases: A Systematic Review and Pooled Oncological Analyses

The impact of Kirsten rat sarcoma (KRAS) status on local tumor progression after surgical ablation of colorectal liver metastases

BACKGROUND

Kirsten rat sarcoma mutation was reported to adversely affect local tumor control after percutaneous ablation of colorectal liver metastasis. Nevertheless, the effect of Kirsten rat sarcoma mutation on surgical ablation has not been investigated in the literature. The aim of this study is to analyze the impact of Kirsten rat sarcoma mutation on local recurrence after surgical ablation of colorectal liver metastasis.

METHODS

This was an institutional review board-approved study of patients who underwent surgical ablation of colorectal liver metastasis between 2005 and 2023 at a single center and underwent Kirsten rat sarcoma testing with ≥1 year follow-up. Local recurrence was analyzed using univariate Kaplan-Meier and multivariate Cox hazard models.

RESULTS

A total of 163 patients with 424 lesions fulfilled inclusion criteria. Fifty (30.7%) patients received radiofrequency ablation and 113 (69.3%) patients received microwave ablation. Fifty-seven patients (32.2%) with 177 lesions were found to have a Kirsten rat sarcoma mutation. Patients with Kirsten rat sarcoma mutation had a larger number of tumors, percentage of posteriorly located tumors, and tumor burden score compared with those with wild-type Kirsten rat sarcoma. Nevertheless, there was no difference between the groups regarding local recurrence per lesion (15% vs 17%, respectively, P = not significant). Independent predictors of local recurrence included tumor size, ablation margin, and blood vessel proximity for radiofrequency ablation compared with tumor size and ablation margin for microwave ablation.

CONCLUSION

There was no effect of Kirsten rat sarcoma mutations on local recurrence after surgical radiofrequency ablation or microwave ablation of colorectal liver metastasis in this study. Tumor size and ablation margin remained as independent predictors.

Microwave ablation for liver metastases from colorectal cancer: A comprehensive review of clinical efficacy and safety

Microwave ablation (MWA) is emerging as a highly effective treatment for colorectal liver metastases (CRLMs). This review explores the advantages of MWA compared to other ablative techniques such as radiofrequency ablation and cryoablation and highlights its clinical efficacy, safety, and technical considerations. MWA offers significant benefits, including higher intratumoral temperatures, larger ablation zones, and reduced susceptibility to the heat-sink effect, which make it particularly suitable for tumors near large blood vessels. This review details the patient selection criteria, procedural approaches, and the use of advanced imaging techniques to improve the precision and effectiveness of MWA. Clinical outcomes indicate that MWA achieves high rates of complete tumor ablation and long-term survival with a favorable safety profile. This review is significant because it provides updated insights into the expanding role of MWA in treating unresectable CRLM and its potential as an alternative to surgical resection for resectable tumors. By summarizing recent studies and clinical trials, this review highlights the comparative effectiveness, safety, and integration with systemic therapies of MWA. In conclusion, MWA is a promising treatment option for CRLM and offers outcomes comparable to or better than those of other ablative techniques. Future research should focus on optimizing technical parameters, integrating MWA with systemic therapies, and conducting large-scale randomized controlled trials to establish standardized treatment protocols. Advancing our understanding of MWA will enhance its application and improve long-term survival and quality of life for patients with CRLM.

How Can We Improve the Survival of Patients with Colorectal Liver Metastases Using Thermal Ablation?

Thermal ablation has been widely used for patients with small colorectal liver metastases (CRLMs), even for resectable cases; however, solid evidence has been scarce. (1) Thermal ablation versus liver resection. Some propensity-score matching studies using patients with balanced baseline characteristics have confirmed less invasiveness and the comparable survival benefits of thermal ablation to liver resection. A more recent pivotal randomized controlled trial comparing thermal ablation and liver resection was presented during the American Society of Clinical Oncology 2024 meeting. Diameter ≤ 3 cm, ten or fewer resectable and ablatable CRLMs were assigned to thermal ablation or liver resection. No differences were observed in the overall survival and local and distant progression-free survival with less morbidity. (2) Combination of thermal ablation and liver resection. Four matching studies demonstrated comparable data between the combination and liver resection alone groups in the long-term survival and recurrence rates without increasing the postoperative complication rates. The selection of the two approaches depends primarily on the number, size, and location of the CRLMs. (3) Chemotherapy in combination with thermal ablation. A propensity-score matching study comparing thermal ablation ± neoadjuvant chemotherapy was conducted. The addition of neoadjuvant chemotherapy was an independent predictive factor for good progression-free survival without increasing morbidity. Two randomized controlled trials demonstrated that additional thermal ablation to systemic chemotherapy can improve the overall survival for initially unresectable CRLMs. (4) Conclusions. Thermal ablation can provide survival benefits for patients with CRLMs in various situations, keeping adequate indications.

Ultrasound-guided intraoperative liver ablation - retrospective review of indications and outcomes

AIM

To define the indications and outcomes of intraoperative ablation of hepatic malignancies.

MATERIALS AND METHODS

This retrospective study comprises 27 patients (male/female: 19/8; mean age: 56 ± 13) undergoing intraoperative ablation (IOA) of liver tumours between July 2001 and August 2021 for 42 tumours, including colorectal liver metastasis (CRLM) (n = 27), hepatocellular carcinoma (HCC)(n = 14), and ovarian cancer metastasis (n = 1). The mean tumour diameter was 2.1 cm ± 1.3 (range, 0.6-5.6 cm). The median imaging follow-up was 26.3 months ± 25.6 (range: 0.13-161.6). Technical success (TS), local tumour progression (LTP), and local progression-free survival (LPFS) were calculated leveraging the Kaplan-Meier method. Adverse events (AE) were categorised according to SIR guidelines.

RESULTS

Indications for IOA include concurrent partial hepatectomy (n = 9), intraoperative detection of a new tumour (n = 4), lack of a safe percutaneous trajectory (n = 3) or clamp of hilum (n = 1). In 7 patients, surgeons made independent decisions for IOA not based on established criteria. Of 32 ablated tumours among 25 patients with available follow-up, TS was achieved for 31 tumours (97%). LTP was detected in 32% of cases at a median of 13.7 months. LPFS at 1,2,3,5 years were 82%, 60%, 51%, 51%. AE rate was 55.5% addressed with minimal or no interventions in 80% of cases. One patient with HCC died of liver failure.

CONCLUSION

The indications for IOA are concurrent partial hepatectomy, intraoperative detection of a new tumour, and suboptimal percutaneous ablation. IOA is effective with high TS. LTP is high. AE rate is relatively high; however, no significant treatment is required in most cases.

Radiofrequency ablation versus microwave ablation for colorectal liver metastases: long-term results of a retrospective cohort surgical experience

Background

Ablation is an alternative treatment modality for selected patients with colorectal liver metastases (CRLMs). Although initially widely performed via radiofrequency ablation (RFA), more recently, microwave ablation (MWA) is being preferred due to its perceived superiority in creating the ablation zones. The aim of this study is to compare the long-term efficacy of these two modalities performed surgically.

Methods

Patients undergoing surgical liver ablation from 2005-2023 at a tertiary center by a single surgeon for CRLM were included in a retrospective institutional review board-approved study. Outcomes were compared using Wilcoxon, Chi-square, Kaplan-Meier, and Cox multivariate regression analyses. Continuous data are presented as median (interquartile range).

Results

There were a total of 242 patients. Laparoscopic RFA was done in 121 patients with 303 lesions and laparoscopic MWA in 121 patients with 300 lesions. There was no difference between the groups regarding operative time (161 vs. 147 minutes, respectively, P=0.4), perioperative morbidity (3% vs. 8%, respectively, P=0.2) or hospital stay (1 vs. 1 day, P=0.05). Local recurrence (LR) per lesion with at least 1 year of imaging follow-up was 29% in the RFA and 13% in the MWA group (P<0.001). Based on univariate survival analysis, tumor size, blood vessel proximity, ablation margin, and ablation modality were independent predictors of LR. To control these variables, direct matching was performed. Each cohort included 189 lesions. Kaplan-Meier analysis of these cohorts showed increased LR-free survival in the MWA group vs. the RFA group (P=0.005).

Conclusions

This large study confirms our initial observation that local tumor control rate is better after MWA vs. RFA.

Recurrence patterns after complex multimodality therapy and hepatic arterial infusion for colorectal liver metastases: A reflection of biology and technique

BACKGROUND AND METHODS

We characterized colorectal liver metastasis recurrence and survival patterns after surgical resection and intraoperative ablation ± hepatic arterial infusion pump (HAIP) placement. We estimated patterns of recurrence and survival in patients undergoing contemporary multimodal treatments. Between 2017 and 2021, patient, tumor characteristics, and recurrence data were collected. Primary outcomes included recurrence patterns and survival data based on operative intervention.

RESULTS

There were 184 patients who underwent hepatectomy and intraoperative ablation. Sixty patients (32.6%) underwent HAIP placement. A total of 513 metastases were ablated, median total of 2 ablations per patient. Median time to recurrence was 31 [22-40] months. Recurrence patterns included tumor at ablative margin on first scheduled postoperative imaging (8, 4.3%), local tumor recurrence at ablative site (69, 37.5%), and non-ablated liver tumor recurrence (38, 20.6%). In patients who underwent HAIP placement, the rate of liver recurrence was reduced (45% vs 70.9%, p = 0.0001). Median overall survival was 64 [41-58] months and prolonged survival was associated with HAIP treatment (85 [66-109] vs 60 [51-70] months.

CONCLUSIONS AND DISCUSSION

Hepatic recurrence is common and combination of intraoperative ablation and HAIP treatments were associated with prolonged survival. These data may reflect patient selection however, future work will clarify preoperative tumor and patient characteristics that may better predict recurrence expectations.

Less contrast, more clarity, innovative visualization technique for management of multiple colorectal liver metastases using microwave ablation through a portal venous access

Colorectal cancer, a leading cause of cancer-related deaths, often results in liver metastases, with about half of patients affected. For those ineligibles for surgery, percutaneous microwave ablation (MWA) offers a viable alternative. Conventionally, visualizing liver lesions prior to MWA demands significant IV contrast, often needing repeated sessions. We introduce a technique using minimal IV contrast to treat multiple metastatic lesions simultaneously. A case of a 47-year-old male with stage 4 colorectal adenocarcinoma and multiple liver metastases is presented. Instead of the typical 100-150 cc of IV contrast, our method used just 25 cc, successfully ablating 6 hepatic metastases in 1 session. This approach not only reduces contrast volume but also optimizes treatment efficiency.

Oligometastatic Colorectal Cancer: A Review of Definitions and Patient Selection for Local Therapies

PURPOSE

Nearly one-third of patients diagnosed with colorectal cancer (CRC) will ultimately develop metastatic disease. While a small percentage of patients can be considered for curative resection, more patients have limited disease that can be considered for local therapy. Challenges remain in defining oligometastatic CRC as well as developing treatment strategies guided by high level evidence.

METHODS

In this review, we present the challenges in defining oligometastatic CRC and summarize the current literature on treatment and outcomes of local therapy in patients with metastatic CRC.

RESULTS

For patients with liver- and/or lung-confined CRC metastases, surgical resection is the standard of care given the potential for long-term progression-free and overall survival. For patients with liver- or lung-confined disease not amenable to surgical resection, non-surgical local therapies, such as thermal ablation, hepatic arterial infusion pump (HAIP), or stereotactic body radiation therapy (SBRT), should be considered. For patients with more advanced disease, such as lymph node or bony metastases, the role of metastasis-directed therapy is controversial. Emerging data suggests that SBRT to ablate all metastases can improve progression-free and overall survival.

CONCLUSION

Multidisciplinary management is critical for patients with metastatic CRC due to the complexity of their cases and the nuanced patient, tumor, biological, and anatomical factors that must be weighed when considering local therapy. High-quality prospective randomized data in CRC are needed to further clarify the role of local ablative therapy in patients with unresectable oligometastatic CRC with ongoing studies including the RESOLUTE trial (ACTRN12621001198819) and the upcoming NCTN ERASur trial (NCT05673148).

Combining Radiofrequency Ablation with Hepatic Resection for Liver-Only Colorectal Metastases: A Propensity-Score Based Analysis of Long-Term Outcomes

BACKGROUND

Combining liver resection (LR) with radiofrequency ablation (RFA) is nowadays an accepted option for treating colorectal liver metastases (CRLMs), but the number of lesions ablated is regularly described as a recurrence risk factor. In this study, we report our experience and determine the impact of RFA on long-term outcomes.

METHOD

This is a retrospective study including patients undergoing LR with or without RFA for CRLM. All variables influencing disease-free survival (DFS) and disease-specific survival (DSS) were examined through a Cox regression analysis before and after propensity-score matching (PSM).

RESULTS

Among the 128 patients included, 71 (55.5%) underwent LR alone and 57 (44.5%) underwent LR+RFA. With univariate analysis, LR+RFA showed a significantly worse DFS than LR alone (p = 0.028), which was not confirmed after PSM (p = 0.064). Thermal ablation did not influence DSS before or after matching (p = 0.282 and p = 0.189). When analyzing the subgroups of patients according to number of RFAs performed, no difference in long-term outcomes was observed (after PSM: p = 0.192 for DFS and p = 0.624 for DSS). Analysis of site of recurrence revealed that neither performing an RFA (p = 0.893) nor the number of lesions ablated (p = 0.093, p = 0.550, and p = 0.087 for 1, 2, and ≥ 2 RFAs) were associated with an increased risk of liver-only relapse.

DISCUSSION

In the setting of a parenchymal sparing strategy, combining RFA with LR is safe in terms of oncological outcomes. Tumor burden, rather than RFA performed, independently influences risk of recurrence and patient survival.

Prediction of Local Tumor Progression After Microwave Ablation in Colorectal Carcinoma Liver Metastases Patients by MRI Radiomics and Clinical Characteristics-Based Combined Model: Preliminary Results

PURPOSE

To investigate the predictability of local tumor progression (LTP) after microwave ablation (MWA) in colorectal carcinoma liver metastases (CRLM) patients by magnetic resonance imaging (MRI) radiomics and clinical characteristics-based combined model.

MATERIALS AND METHODS

Forty-two consecutive CRLM patients (67 tumors) with post-MWA complete response at 1st month MRI were included in this retrospective study. One hundred and eleven radiomics features were extracted for each tumor and for each phase by manual segmentation from pre-treatment MRI T2 fat-suppressed (Phase 2) and early arterial phase T1 fat-suppressed sequences (Phase 1). A clinical model was constructed using clinical data, two combined models were created with feature reduction and machine learning by combining clinical data and Phase 2 and Phase 1 radiomics features. The predicting performance for LTP development was investigated.

RESULTS

LTP developed in 7 patients (16.6%) and 11 tumors (16.4%). In the clinical model, the presence of extrahepatic metastases before MWA was associated with a high probability of LTP (p < 0.001). The pre-treatment levels of carbohydrate antigen 19-9 and carcinoembryonic antigen were higher in the LTP group (p = 0.010, p = 0.020, respectively). Patients with LTP had statistically significantly higher radiomics scores in both phases (p < 0.001 for Phase 2 and p = 0.001 for Phase 1). The classification performance of the combined model 2, created by using clinical data and Phase 2-based radiomics features, achieved the highest discriminative performance in predicting LTP (p = 0,014; the area under curve (AUC) value 0.981 (95% CI 0.948-0.990). The combined model 1, created using clinical data and Phase 1-based radiomics features (AUC value 0,927 (95% CI 0.860-0.993, p < 0.001)) and the clinical model alone [AUC value of 0.887 (95% CI 0.807-0.967, p < 0.001)] had similar performance.

CONCLUSION

Combined models based on clinical data and radiomics features obtained from T2 fat-suppressed and early arterial-phase T1 fat-suppressed MRI are valuable markers in predicting LTP after MWA in CRLM patients. Large-scale studies with internal and external validations are needed to come to a firm conclusion on the predictability of radiomics models in CRLM patients.

Thrombus formation in the suprahepatic inferior vena cava after microwave ablation in patients with hepatic metastasis: a case report

BACKGROUND

Microwave ablation (MWA) via ultrasound guidance is an important tool in the treatment of liver metastases. The most common postoperative complications are abdominal hemorrhage and bile leakage, whereas thrombosis in the suprahepatic inferior vena cava (IVC) is very rare, and clinical management is very difficult when the head end of the thrombus reaches the right atrium.

CASE PRESENTATION

This is a case report of a 52-year-old man with hepatic metastasis 21 months after radical resection of rectal cancer. After chemotherapy combined with targeted therapy, metastasis in segment IV (S4) of the liver was treated with microwave ablation. Two months after treatment, the hepatic metastasis in S4 showed a microwave ablation zone on MRI.Enhanced MRI showed venous thrombosis located in the left hepatic vein and IVC, and the head of the thrombus reached the right atrium. After two weeks of anticoagulation and thrombolytic treatment, the follow-up MRI showed that the venous thrombus had nearly disappeared.

CONCLUSION

When liver metastases are close to the hepatic vein, clinicians should pay attention to the occurrence of hepatic vein and IVC thrombosis following MWA; through early diagnosis and anticoagulation, pulmonary thromboembolism (PTE) can be minimized.

Ablative Therapy in Non-HCC Liver Malignancy

Surgical extirpation of liver tumors remains a proven approach in the management of metastatic tumors to the liver, particularly those of colorectal origin. Ablative, non-resective therapies are an increasingly attractive primary therapy for liver tumors as they are generally better tolerated and result in far less morbidity and mortality. Ablative therapies preserve greater normal liver parenchyma allowing better post-treatment liver function and are particularly appropriate for treating subsequent liver-specific tumor recurrence. This article reviews the current status of ablative therapies for non-hepatocellular liver tumors with a discussion of many of the clinically available approaches.

Ablation versus resection for resectable colorectal liver metastases - Health care related cost and survival analyses from a quasi-randomised study

BACKGROUND

The aim of this study was to compare healthcare related costs and survival in patients treated with microwave ablation (MWA) versus surgical resection for resectable colorectal liver metastases (CRLM), in patients from a quasi-randomised setting.

METHODS

The Swedish subset of data from a prospective multi-centre study investigating survival after percutaneous computer-assisted Microwave Ablation VErsus Resection for Resectable CRLM (MAVERRIC study) was analysed. Patients with CRLM ≤ 3 cm amenable to ablation and resection were considered for study inclusion only on even calendar weeks, while treated with gold standard resection every other week, creating a quasi-randomised setting. Survival and costs (all inpatient hospital admissions, outpatient visits, oncological treatments and radiological imaging) in the 2 years following treatment were investigated.

RESULTS

MWA (n = 52) and resection (n = 53) cohorts had similar baseline patient and tumour characteristics and health care consumption within 1 year prior to CRLM treatment. Treatment related morbidity and length of stay were significantly higher in the resected cohort. Overall health care related costs from decision of treatment and 2 years thereafter were lower in the MWA versus resection cohort (mean ± SD USD 80'964±59'182 versus 110'059±59'671, P < 0.01). Five-year overall survival was 50% versus 54% in MWA versus resection groups (P = 0.95).

CONCLUSIONS

MWA is associated with decreased morbidity, time spent in medical facilities and healthcare related costs within 2 years of initial treatment with equal overall survival, highlighting its benefits for patient and health care systems.

Crosstalk between microwave ablation and ferroptosis: The next hot topic?

Microwave ablation has been one form of thermal ablation in treatments for many tumors, which can locally control unresectable tumors. Ferroptosis is iron-dependent cell death caused by the cumulative reactive oxygen species and lipid peroxidation products. Recently, increasing evidence has shown that ferroptosis might play a vital role in MWA-induced tumor suppression. In this article, we briefly illustrate the concept of ferroptosis, the related signal pathways and inducers, the basic principle of microwave ablation in killing tumors, and the key molecules released after microwave ablation. Then, we describe the cross-talking molecules between microwave ablation and ferroptosis, and discussed the potential mechanism of microwave ablation-induced ferroptosis. This review explores the therapeutic target of ferroptosis in enhancing the systemic antitumor effect after microwave ablation, providing theoretical support in combinational microwave ablation with pro-ferroptosis therapy.

Surgery combined with intra-operative microwaves ablation for the management of colorectal cancer liver metastasis: A case-matched analysis and evaluation of recurrences

Background

Hepatic resection is the only chance of cure for a subgroup of patients with colorectal cancer liver metastasis. As the oncologic outcomes of intra-operative microwaves ablation combined with hepatic resection still remain uncertain in this setting, we aimed to compare this approach with surgery alone in patient's candidate to metastases resection with radical intent.

Methods

Using a case-matched methodology based on age, gender, American Society of Anesthesiology score, Body Mass Index, and burden that take in consideration the number and maximum size of lesions, 20 patients undergoing hepatic resection plus intra-operative microwaves (SURG + IMW group) and 20 patients undergoing hepatic resection alone (SURG group), were included. Relapse-free Survival and post-resection Overall Survival were compared between patients of two groups.

Results

At the median follow up of 22.4 ± 17.8, 12/20 patients (60%) in SURG +IMW group and 13/20 patients (65%) in the SURG group experienced liver metastasis recurrence (p=0.774). None of them had recurrence at the same surgical or ablation site of the first hepatic treatment. 7/12 patients in the SURG+IMW group and 7/13 patients in the SURG group underwent at least one further surgical treatment after relapse (p = 1.000). No difference was reported between the two groups in terms of Relapse-free Survival (p = 0.685) and post-resection Overall Survival (p = 0.151). The use of intra-operative microwaves was not an independent factor affecting Relapse-free Survival and post-resection Overall Survival at univariate and multivariate analysis.

Conclusions

Patients with colorectal cancer liver metastasis undergoing surgery plus intra-operative microwaves have similar post-operative results compared with surgery alone group. The choice between the two approaches could be only technical, depending on the site, number, and volume of the metastases. This approach could also be used in patients with liver metastasis relapse who have already undergone hepatic surgery.

Disappearing Colorectal Liver Metastases: Do We Really Need a Ghostbuster?

The development of new systemic treatment strategies has resulted in a significant increase in the response rates of colorectal liver metastases (CRLM) in the last few years. Although the radiological response is a favorable prognostic factor, complete shrinkage of CRLM, known as disappearing liver metastases (DLM), presents a therapeutic dilemma, and proper management is still debated in the literature. In fact, DLM is not necessarily equal to cure, and when resected, pathological examination reveals in more than 80% of patients a variable percentage of the tumor as residual disease or early recurrence in situ. Moreover, while a higher incidence of intrahepatic recurrence is documented in small series when surgery is avoided, its clinical significance for long-term OS is still under investigation. In light of this, a multidisciplinary approach and, in particular, radiologists’ role is needed to assist the surgeon in the management of DLM, thanks to emerging technology and strategy. Therefore, the aim of this review is to provide an overview of the DLM phenomenon and current management.

Precision Imaging Guidance in the Era of Precision Oncology: An Update of Imaging Tools for Interventional Procedures

Interventional oncology (IO) procedures have become extremely popular in interventional radiology (IR) and play an essential role in the diagnosis, treatment, and supportive care of oncologic patients through new and safe procedures. IR procedures can be divided into two main groups: vascular and non-vascular. Vascular approaches are mainly based on embolization and concomitant injection of chemotherapeutics directly into the tumor-feeding vessels. Percutaneous approaches are a type of non-vascular procedures and include percutaneous image-guided biopsies and different ablation techniques with radiofrequency, microwaves, cryoablation, and focused ultrasound. The use of these techniques requires precise imaging pretreatment planning and guidance that can be provided through different imaging techniques: ultrasound, computed tomography, cone-beam computed tomography, and magnetic resonance. These imaging modalities can be used alone or in combination, thanks to fusion imaging, to further improve the confidence of the operators and the efficacy and safety of the procedures. This article aims is to provide an overview of the available IO procedures based on clinical imaging guidance to develop a targeted and optimal approach to cancer patients.