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

Abstract

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.

Key Words: Microwave ablation; Colorectal liver metastases; Thermal ablation techniques; Clinical outcomes; Tumor ablation safety

Core Tip: This review focuses on the application of microwave ablation (MWA) as a treatment for colorectal liver metastasis. MWA offers advantages such as higher intratumoral temperatures, larger ablation zones, and reduced heat-sink effects compared to other techniques such as radiofrequency ablation. This review also discusses the safety and clinical outcomes of MWA and emphasizes its potential as an effective treatment for colorectal liver metastasis. Despite its benefits, this review highlights the need for further research to confirm long-term efficacy and optimize patient selection for better outcomes.

INTRODUCTION

Colorectal liver metastases (CRLMs) pose a substantial global health challenge. Colorectal cancer (CRC) ranks as the third most common cancer worldwide with approximately 1.9 million new cases diagnosed annually. Liver metastases develop in up to 50% of CRC patients during illness, and liver involvement is a leading cause of mortality. Globally, CRC is responsible for nearly 935000 deaths per year, and liver metastases play a major role in this statistic[1,2]. Although early detection and treatment have been improving, the survival rates for CRLM patients remain low, especially when the metastases are unresectable[3].

The management of CRLM has significantly advanced over time. Surgical resection remains the gold standard for treating resectable CRLM and provides the best opportunity for long-term survival, where the 5-year survival rates are 22%-58% in selected cases[3]. However, only 15%-25% of patients are diagnosed with resectable disease, and this determination is often limited by the size, number, and location of liver metastases and the patient’s overall health and comorbidities[4]. For patients with unresectable CRLM, systemic chemotherapy remains the primary treatment option. However, chemotherapy alone rarely results in long-term survival, and most patients eventually experience disease progression[5].

The limitations of current treatments have prompted interest in alternative therapies, especially for patients with unresectable liver metastases. Thermal ablation techniques such as radiofrequency ablation (RFA) and microwave ablation (MWA) have emerged as promising methods for the local control of liver metastases. MWA offers several advantages over RFA, including higher intratumoral temperatures, larger ablation zones, and reduced sensitivity to the heat-sink effect near blood vessels[6]. These benefits make MWA a preferable option for treating liver metastases near major vascular structures, and its minimally invasive nature broadens its clinical applications[7].

Despite its potential, gaps remain in understanding the long-term efficacy of MWA, particularly in comparison to surgical resection and systemic treatments. This review aims to comprehensively analyze MWA as a treatment for CRLMs. The mechanisms, clinical efficacy, and safety profile of MWA were examined, and MWA was compared with other treatments such as RFA and surgical resection. Additionally, this review discusses guidelines for patient selection, technical considerations, and future research directions in this field.

GENERAL GUIDELINES FOR MWA IN CRLM PATIENTS

MWA has emerged as a promising treatment for CRLM and a minimally invasive alternative to traditional surgical resection. The selection of patients for MWA is critical and based on several factors, including the number, size, and location of liver metastases. Typically, MWA is most effective for tumors less than 3 cm in diameter, and multiple tumors can be simultaneously treated using multiple probes[8]. MWA is particularly advantageous for tumors near large vessels, where the heat-sink effect can reduce the efficacy of other thermal ablation techniques such as RFA[9]. Moreover, the choice among percutaneous, laparoscopic, or open surgical approaches depends on the accessibility of the tumor and overall health status of the patient[10].

Contraindications for MWA include tumors that are too large or numerous and those near critical structures such as the bile ducts or major blood vessels. Patients with severe comorbidities or poor overall health may not be ideal candidates for this procedure[11]. Pre-procedural imaging is essential for planning the ablation and ensuring the safety and efficacy of the treatment. Advanced imaging techniques such as computed tomography (CT), magnetic resonance imaging (MRI), or ultrasound (US) are used to guide the placement of MWA probes and monitor the ablation in real time[5]. Post-procedural imaging is also crucial for assessing the success of the ablation and detecting any immediate complications[12].

In terms of outcomes, studies have shown that MWA can achieve comparable overall survival (OS) and progression-free survival rates to surgical resection for selected patients with CRLM. For example, Puijk et al[7] demonstrated that MWA was effective for small, unresectable CRLMs with similar survival rates to those of patients undergoing hepatic resection. Complications related to MWA are generally rare and include minor issues such as pain at the ablation site and more serious complications such as bile duct injury or liver abscesses, which are relatively rare[7]. Proper patient selection, meticulous procedural planning, and advanced imaging techniques are key to optimizing the outcomes of MWA in patients with CRLM[13].

EFFICACY OF MWA FOR UNRESECTABLE CRLM

MWA has shown significant promise in the treatment of unresectable CRLM as a viable alternative to patients who are not candidates for surgical resection. The primary advantage of MWA is its ability to achieve high intratumoral temperatures, which results in effective tumor ablation with minimal heat-sink effects, particularly in tumors near large blood vessels. Studies have demonstrated that MWA can achieve comparable, if not superior, outcomes to those of other thermal ablation techniques such as RFA in terms of OS and progression-free survival[8]. For example, a systematic review by Lucchina et al[14] reported that MWA provided excellent local control rates for intermediate-sized CRLM (3-5 cm), and the local control rates were 22%-90% depending on the study and tumor characteristics.

In clinical practice, MWA has been effectively used in combination with systemic chemotherapy to downsize tumors and convert previously unresectable CRLM to resectable states. Ammori et al[15] highlighted that combining hepatic artery infusion chemotherapy with systemic chemotherapy could significantly downsize the tumor, enable complete resection and/or ablation in approximately 25% of patients with initially unresectable CRLM. This combination strategy has been associated with improved long-term survival. The median survival extended up to 59 months in patients who successfully underwent complete resection or ablation, compared to 16 months in those who did not convert[15].

Additionally, the efficacy of MWA is supported by its favorable safety profile and minimal incidence of complications. Studies indicate that MWA is associated with lower complication rates than RFA, and the procedural time for MWA is significantly shorter, so it is an attractive option for both patients and clinicians[16,17]. Clinical outcomes from MWA treatments show promising survival benefits with global recurrence-free survival (RFS) rates at 1, 3, and 5 years of 65.1%, 44.6%, and 34.3%, respectively, and the OS rates at the same intervals of 86.7%, 59.6%, and 44.8%, respectively[2]. These outcomes are comparable to those achieved with surgical resection, underscoring MWA’s potential as a primary or adjunctive treatment modality for unresectable CRLM.

MWA FOR RESECTABLE CRLM

MWA is increasingly considered a viable treatment option for patients with resectable CRLM, especially those who may not be ideal candidates for surgical resection due to comorbidities or other risk factors. Several studies have evaluated the efficacy of MWA over surgical resection and provided insights into its potential as an alternative treatment modality. A systematic review and meta-analysis by Di Martino et al[18] examined the local ablative therapies for resectable CRLM, including MWA. The review found that MWA demonstrated favorable outcomes in terms of disease-free survival (DFS) and OS compared to other ablative techniques, such as RFA and cryoablation (CA)[18]. The median 3-year and 5-year OS rates for MWA were 70% and 55%, respectively, which indicates its potential efficacy in managing resectable CRLM.

Despite these promising results, hepatic resection remains the gold standard for treating resectable CRLM with superior local control and survival benefits. However, MWA has shown comparable results in specific patient subsets. For example, a study by Tinguely et al[4] on stereotactic MWA for resectable CRLM demonstrated non-inferior OS compared to hepatic resection: The 3-year OS rates were 78% for MWA and 76% for resection. Additionally, MWA was associated with lower overall and major complication rates, making it a safer alternative for patients with greater surgical risk. The study also highlighted the advantages of MWA in terms of hepatic retreatment options, which could be beneficial for long-term disease management[4]. The use of MWA for resectable CRLM also offers advantages in terms of procedural simplicity and recovery time. Gavriilidis et al[19] conducted a network meta-analysis that compared the recurrence rates and survival benefits among MWA, RFA, and hepatic resection. These findings suggest that although hepatic resection remains the preferred treatment for optimal disease-free and OS, MWA serves as a valuable alternative for patients who are unsuitable for surgery due to various constraints. One study emphasized that MWA could be effectively integrated into multimodal treatment plans to potentially improve the patient outcomes when MWA is combined with systemic therapies[19].

TECHNICAL CONSIDERATIONS AND APPROACHES

MWA for CRLM involves meticulous planning and advanced imaging techniques to ensure precise targeting and effective tumor destruction. The choice of imaging guidance is critical and includes US, CT, and MRI. Each modality has advantages and limitations. For example, US is widely available and provides real-time guidance, but its efficacy can be compromised in patients with poor acoustic windows or deeply situated tumors[20]. CT guidance offers high spatial resolution and is particularly useful for targeting tumors in the hepatic dome or near the diaphragm[21]. MRI, which is less commonly used because of its relatively high cost and limited availability, provides superior soft-tissue contrast and is invaluable in detecting small lesions and assessing ablation margins[22]. The procedural approach to MWA can be percutaneous, laparoscopic, or open surgical. Each option has specific indications based on the tumor location, patient anatomy, and overall health status. Percutaneous MWA is the least invasive method and often preferred for superficial or easily accessible lesions. Laparoscopic MWA enables direct visualization and manipulation of the liver, which is beneficial for tumors near critical structures such as bile ducts or major vessels[23]. Open surgical MWA is typically reserved for patients undergoing concomitant hepatic resection or those with complex tumor burdens that require extensive manipulation[16]. The use of advanced assistive technologies such as fusion imaging, which combines real-time US with CT or MRI data, has significantly improved the accuracy and efficacy of MWA in challenging cases[22,24].

The technical success and clinical outcomes of MWA are influenced by several factors, including the size and number of tumors, their proximity to large blood vessels, and the presence of the heat-sink effect. Studies have shown that MWA can achieve high rates of complete ablation for tumors smaller than 3 cm, with minimal complications[21,25]. The heat-sink effect, where blood flow in adjacent vessels dissipates the heat generated by ablation, can reduce the efficacy of thermal ablation. However, the ability of MWA to generate higher temperatures overcomes this limitation and makes it more effective than RFA for treating tumors adjacent to large vessels[17,25]. Additionally, the use of artificial ascites or pneumoperitoneum can create a safe distance between the tumor and adjacent organs and reduce the risk of thermal injury[21]. In conclusion, the technical considerations and approaches for MWA in CRLM patients require a multidisciplinary effort and combine advanced imaging techniques with precise procedural planning to optimize outcomes. The choice of imaging modality and procedural approach should be tailored to the anatomy and tumor characteristics of individual patients to ensure effective and safe ablation. Continued advancements in imaging and assistive technologies are expected to increase the precision and efficacy of MWA in the treatment of CRLM[16,26].

MWA is generally well tolerated, but as an invasive procedure, it is associated with potential complications. The most commonly reported complications include bleeding, bile duct injury, infection, and thermal damage to adjacent organs[27]. Complication rates vary depending on factors such as the tumor size, location, and experience of the surgical team. Notably, MWA is less affected by the heat-sink effect than other ablation techniques, but its high thermal efficiency can increase the risk of unintended tissue damage, especially when treating tumors near major vessels or bile ducts[16].

The choice of surgical approach (open surgical resection or laparoscopic surgery) can influence the complication rates and overall success of the procedure. Performing MWA during open surgical resection enables direct visualization of the liver and precise targeting of the tumor, reduces the risk of incomplete ablation and facilitates the immediate management of complications. In addition, laparoscopic MWA is a minimally invasive option with reduced recovery time and less postoperative pain[27]. However, the laparoscopic approach may be technically challenging, particularly for tumors located deep within the liver or near critical structures, and it requires advanced imaging guidance to ensure precise ablation[28,29]. The decision to perform MWA during open or laparoscopic resection should be guided by the tumor characteristics, patient condition, and surgeon expertise to balance the risks and benefits of each approach[30,31].

CLINICAL OUTCOMES AND SAFETY

MWA has demonstrated significant efficacy in the treatment of CRLM. Several studies reported high rates of complete tumor ablation and favorable long-term survival outcomes. In a meta-analysis by Facciorusso et al[32], the OS and DFS rates for MWA were comparable to those of RFA, and a notable reduction in long-term recurrence rates favors MWA. The 5-year OS rate for MWA was approximately 81.9%, which indicates its potential as an effective treatment modality for CRLM. Table 1 shows the clinical outcomes and safety data from key studies that compare MWA with other ablative techniques and resection for CRLM.

Table 1 Summary of clinical outcomes and safety in studies comparing microwave ablation with other ablation techniques for colorectal liver metastases.

Ref.	Modality	Follow-up (months)	Complication rate (%)	Local recurrence rate (%)	Overall survival (months)	Disease-free survival (months)
Di Martino et al[18], 2020	MWA vs RFA	36	7	8 (MWA); 12 (RFA)	44.5	38.5
Gavriilidis et al[19], 2021	MWA vs RFA vs HR	36	12	5	32.1	24.5
Mimmo et al[2], 2022	MWA	60	10	6	34.3	22
Tinguely et al[4], 2023	MWA vs HR	60	15	7	58	28
Ammori et al[15], 2013	HAI chemotherapy	60	16	18	47	25
Izzo et al[8], 2019	RFA vs MWA	66	10.5	7.9	50	22
Lucchina et al[14], 2016	MWA	12	10	6	32	18
Meloni et al[16], 2017	MWA	36	15	5.2	24	24
Vogl et al[17], 2017	MWA	36	5	5.2	32	24
Carrafiello et al[29], 2008	MWA	12	5	6	36	12
Cornelis et al[36], 2017	MWA	60	5	6	32	18
Facciorusso et al[32], 2020	MWA vs RFA	39	7	4.3 (MWA); 7.5 (RFA)	39	22
Moussa et al[40], 2019	MWA	24	8	5	24	24
Spiliotis et al[41], 2021	MWA vs RFA	24	12	6	24	24
Tan et al[38], 2019	MWA vs RFA	24	6	12 (MWA); 15 (RFA)	24	24
Vietti Violi et al[39], 2018	MWA vs RFA	24	12	12 (MWA); 14 (RFA)	24	24
Zheng et al[42], 2018	TACE vs TACE + MWA	45	17	6	17.1	6.7

This table provides a comprehensive overview of the clinical outcomes and safety across various studies that evaluated microwave ablation in comparison with other ablation techniques such as radiofrequency ablation, hepatic resection, and other modalities. The table summarizes key metrics, including the follow-up duration, complication rates, local recurrence rates, overall survival, and disease-free survival. These metrics highlight the relative effectiveness and safety profiles of microwave ablation and its potential advantages or limitations in the treatment of colorectal liver metastases. MWA: Microwave ablation; RFA: Radiofrequency ablation; HR: Hepatic resection; HAI: Hepatic artery infusion; TACE: Transarterial chemoembolization.

The safety profile of MWA is also well documented. Several studies highlighted its low incidence of major complications. Ierardi et al[33] conducted a study to compare MWA and RFA for hepatic lesions and reported that MWA was associated with a lower incidence of complications such as bile duct injury and hemorrhage. This study also emphasized the advantage of MWA in reducing the heat-sink effect, which enhances its efficacy in treating tumors near large blood vessels. Similarly, Hu et al[34] compared MWA with CA for hepatocellular carcinoma (HCC) in high-risk locations and concluded that MWA provided comparable OS and RFS rates with minimal complications.

Advanced imaging technologies have improved the outcomes of MWA. Asvadi et al[21] demonstrated that CT-guided MWA of hepatic dome tumors resulted in a high technical success rate and a low incidence of major complications. This study also showed that MWA was effective in achieving complete tumor ablation even in challenging anatomical locations and broadened its applicability[21]. An et al[20] reported that US-guided percutaneous MWA for HCC in challenging locations achieved comparable success and survival outcomes with those in less challenging locations, which validates the safety and efficacy of MWA in complex clinical scenarios. In conclusion, the clinical outcomes of MWA for CRLM are promising with high rates of local control and long-term survival. The safety profile of MWA is also favorable with low rates of major complications. The use of advanced imaging technologies has increased the precision and efficacy of MWA and made it a viable and effective treatment option for patients with CRLM.

COMPARISON WITH OTHER ABLATION TECHNIQUES

MWA is one of several thermal ablation techniques to treat CRLM, and RFA is the most commonly compared modality. Both techniques use heat to induce coagulative necrosis of tumors, but MWA offers certain advantages over RFA. MWA achieves higher intratumoral temperatures, larger ablation zones, and shorter ablation times. Additionally, MWA is less affected by the heat-sink effect caused by nearby blood vessels, which makes it more effective in treating tumors near large vascular structures[35,36]. Table 2 summarizes the advantages and disadvantages of MWA compared with other ablation techniques such as RFA, hepatic arterial infusion, and transarterial chemoembolization. This comparison highlights key differences in clinical effectiveness and safety and provides a clearer understanding of when MWA is the preferred option.

Table 2 Advantages and disadvantages of microwave ablation compared with other ablation techniques.

Ref.	Modality	Advantages	Disadvantages
Carrafiello et al[29], 2008	MWA vs other ablation techniques	Higher intratumoral temperatures, larger ablation zones, less heat-sink effect	Requires further studies to confirm long-term effectiveness
Cornelis et al[36], 2017	MWA vs RFA	Less dependent on electrical conductivities, higher temperatures, less desiccation	Insufficient long-term data on oncologic effectiveness
Facciorusso et al[32], 2020	MWA vs RFA	Broader zone of active heating, higher temperatures, shorter treatment times, no heat-sink effect	Broader and less predictable necrosis areas, uncertain if larger ablation zone translates to survival gain
Moussa et al[40], 2019	MWA vs RFA	Overcomes limitations of RFA in lung cancer treatment, higher temperatures, larger ablation zones	Potential complications, need for optimal patient selection
Spiliotis et al[41], 2021	MWA vs RFA	Better oncological outcomes in terms of local tumor progression for HCC	Requires high-quality evidence to confirm superiority
Tan et al[38], 2019	MWA vs RFA	Lower local recurrence rates in laparoscopic ablation	Higher major complication rate in laparoscopic MWA
Vietti Violi et al[39], 2018	MWA vs RFA	Low local tumor progression rates, fewer complications	No significant difference in complications between MWA and RFA
Zheng et al[42], 2018	MWA vs TACE	Improved overall survival, longer time to progression	Higher recurrence rates, potential complications
Ammori et al[15], 2013	HAI chemotherapy vs R/A	Increased conversion to resection/ablation, improved long-term survival	Only 25% of patients respond sufficiently for conversion
Gavriilidis et al[19], 2021	MWA vs HR vs RFA	Less local recurrence, better 3-year and 5-year survival	Significantly younger patients, lower preoperative CEA
Lucchina et al[14], 2016	MWA vs RFA	Higher thermal efficiency, no heat-sink effect, suitable for tumors near vessels	Requires further validation for widespread use
Meloni et al[16], 2017	MWA vs other ablation techniques	High efficacy, fast procedure, good local control	Requires advanced imaging and close follow-up
Mimmo et al[2], 2022	MWA	High local control rates, long-term disease control	Requires optimal patient selection and proper procedural techniques
Tinguely et al[4], 2023	MWA vs HR	Non-inferior overall survival compared to resection, lower complications	Higher retreatment rates compared to resection
Vogl et al[17], 2017	MWA	Shorter ablation time, less pain, less heat sink effect	Needs scientific proof of advantages
Wagstaff et al[46], 2014	MWA vs RFA	Similar oncologic outcomes, better functional and perioperative outcomes	Low risk of residual disease, candidates must be properly informed

This table summarizes the advantages and disadvantages of microwave ablation (MWA) compared to other ablation techniques such as radiofrequency ablation, hepatic arterial infusion, and transarterial chemoembolization. The table highlights the specific benefits of MWA, such as higher intratumoral temperatures, larger ablation zones, and reduced heat-sink effects, and potential drawbacks such as the need for further studies to confirm its long-term effectiveness and higher complication rates in certain contexts. This comparison provides insights into the suitability of MWA for treating colorectal liver metastases and helps understand its role relative to other established therapies. MWA: Microwave ablation; RFA: Radiofrequency ablation; HCC: Hepatocellular carcinoma; TACE: Transarterial chemoembolization; HAI: Hepatic artery infusion; R/A: Resection/ablation; HR: Hepatic resection; CEA: Carcinoembryonic antigen.

In terms of clinical outcomes, several studies have compared the efficacy and safety of MWA and RFA. A systematic review and meta-analysis by Facciorusso et al[32] revealed no significant difference in OS or DFS between the two techniques for HCC. However, MWA tends to have better local tumor control, particularly for larger tumors[37]. Similarly, a meta-analysis by Tan et al[38] reported that MWA had a lower local recurrence rate and a similar complication profile compared with RFA, which highlights potential advantages of MWA in certain clinical scenarios. Another study by Vietti et al[39] conducted a randomized controlled trial comparing MWA and RFA for HCC lesions of 4 cm or smaller. The study revealed that both techniques had similar rates of local tumor progression at two years, but MWA was associated with fewer grade-3 and grade-4 complications. These findings suggest that MWA may be safer for patients with tumors in challenging locations[39]. Furthermore, Moussa et al[40] reviewed the use of MWA in primary lung malignancies and demonstrated its advantages over RFA in terms of achieving higher temperatures and larger ablation zones, which are crucial for effective tumor destruction. CA is another alternative to thermal ablation techniques such as MWA and RFA. CA uses freezing to induce tumor cell death and is particularly useful for tumors near critical structures because of its precision. Hu et al[34] compared MWA and CA for HCC in high-risk locations and reported that both techniques provided comparable OS and RFS rates. However, MWA has a higher rate of local tumor progression and major complications than CA.

In conclusion, although both MWA and RFA are effective thermal ablation techniques to treat CRLM, MWA offers several advantages, particularly in terms of higher temperatures, larger ablation zones, and a reduced heat-sink effect. MWA has shown comparable or superior efficacy in various studies, with a favorable safety profile. However, the choice of ablation technique should be tailored to individual patient and tumor characteristics, and further research is necessary to establish the optimal use of these modalities in clinical practice[41,42].

FUTURE DIRECTIONS AND RESEARCH NEEDS

As the field of MWA for CRLM continues to evolve, several key areas require further investigation to optimize treatment outcomes and expand its applications. One promising avenue is the integration of MWA with systemic therapies, such as chemotherapy and immunotherapy. Studies have shown that combining local ablation with systemic treatments can increase the OS and reduce recurrence rates by targeting both local and distant disease[43,44]. Future research should focus on identifying the most effective combinations and treatment protocols and understanding the underlying mechanisms that drive synergistic effects.

Another important area for future research is the development and refinement of advanced imaging techniques to guide MWA procedures. Current imaging modalities such as US, CT, and MRI provide essential real-time guidance during ablation. However, innovations such as contrast-enhanced US, fusion imaging that combines real-time US with CT or MRI, and high-resolution imaging probes can improve the precision and efficacy of MWA[45]. Studies should investigate the clinical benefits of these advanced imaging techniques and their impact on procedural outcomes, particularly for tumors in challenging locations.

The exploration of the immunomodulatory effects of MWA is another frontier with significant potential. Preclinical and clinical studies suggest that thermal ablation, including MWA, can induce an immune response by promoting the antigen presentation and enhancing the systemic anti-tumor immunity[43]. Investigating how MWA can be used in conjunction with immune checkpoint inhibitors and other immunotherapies can lead to novel treatment strategies that leverage the body’s immune system to combat CRLM. Research in this area should aim to elucidate the mechanisms of immune activation and identify patient populations that may benefit most from these combined approaches. Further studies are necessary to optimize the technical parameters of MWA, such as the power settings, duration of ablation, and probe placement strategies. Comparative research on different ablation devices and techniques can help establish standardized protocols that maximize the treatment efficacy and minimize complications[46]. Long-term follow-up studies are also crucial for evaluating the durability of MWA’s clinical benefits and its role in long-term disease management.

Finally, there is a need for large-scale, multicenter randomized controlled trials to provide robust evidence on the comparative effectiveness of MWA vs other treatment modalities, including surgical resection, RFA, and CA. These studies should aim to clarify the indications for MWA, identify optimal patient selection criteria, and determine the best practices to integrate MWA into multimodal treatment regimens[11]. Such trials will be instrumental in establishing MWA as a standard of care for CRLM and guiding clinical decision-making.

CONCLUSION

MWA offers several advantages in the treatment of CRLM compared to other ablative techniques such as RFA. MWA provides faster heating, larger ablation zones, and reduced sensitivity to the heat-sink effect, so it is particularly suitable for larger or complex tumors and those near blood vessels[47]. Clinical outcomes demonstrate favorable local control rates, low recurrence rates, and good OS, especially in comparison with RFA and hepatic resection[48]. Moreover, the minimally invasive nature of MWA enables shorter procedure times and faster recovery, which enhances the quality of life for patients[16].

However, despite these advantages, the long-term efficacy of MWA, particularly for multi-focal and large metastases, remains under investigation. The current body of evidence highlights the need for well-designed, large-scale randomized controlled trials to confirm the superiority of MWA over other ablation techniques and to establish clear treatment protocols[28]. Future studies should focus on optimizing patient selection, refining ablation techniques, and exploring combinations with systemic therapies to further improve the clinical outcomes[29].

ACKNOWLEDGEMENTS

We would like to express our gratitude to our colleagues and institutional collaborators for their support throughout this research.