New MWA Service

The Radiology Department at the National Cancer Center Benghazi is pleased to announce the availability of a new Microwave Ablation (MWA) service. This significant addition to our department underscores our commitment to providing advanced and comprehensive oncological care to our patients. Microwave ablation represents a minimally invasive, image-guided thermal ablation technique that utilizes electromagnetic waves to induce localized coagulative necrosis within target tissues.[1, 2, 3] This technology offers several advantages over other ablation modalities, such as radiofrequency ablation (RFA), including the ability to achieve faster and more sustained heating of tissues, reach higher intratumoral temperatures, create larger ablation zones, and exhibit less susceptibility to the cooling effects of nearby blood flow, known as the heat sink effect.[2, 3, 4, 5, 6, 7, 8, 9] Furthermore, MWA can be performed with versatility through percutaneous, laparoscopic, or intraoperative approaches, guided by various imaging modalities and under different forms of anesthesia, thereby offering a flexible treatment option for a wide range of clinical scenarios.[1, 2, 8, 10]

To provide a clearer understanding of how microwave ablation compares with other thermal ablation methods currently available, we present the following table adapted from existing literature [5]:

Parameter(s)	Radiofrequency	Microwave	Cryoablation
Set up	++	+++ (quickest)	+
Duration of ablation	++	+++ (shortest)	+
≤3 cm	+++	+++	+++
>3 cm	+ *	++ + *	++ *
≤1.5 cm pleura	+ (pain)	+ (pain, air leak)	+++
Emphysema	++	+++	+
Chest wall	+	++	+++
Mediastinum	+	+	++
Thermal sinks	+	+++ (least)	++
Preservation of collagen	+	+	+++
Coagulopathies	+++	+++	+

The introduction of microwave ablation to our department significantly enhances our capacity to offer minimally invasive treatment options for a variety of oncological conditions. We encourage our esteemed colleagues to consider this service for appropriately selected patients across several organ systems.

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I. Main Indications for Microwave Ablation

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A. Lung Malignancies

• Primary Non-Small Cell Lung Cancer (NSCLC): Microwave ablation is indicated as a primary treatment modality for patients diagnosed with early-stage (Stage IA) Non-Small Cell Lung Cancer who, due to medical comorbidities or personal preference, are not candidates for or decline surgical resection.[4, 5, 11, 12, 13, 14, 15] Furthermore, MWA can be considered for patients experiencing unresectable local recurrences of NSCLC following prior treatment with surgery or radiation therapy.[4, 5, 7, 11, 12] In certain clinical scenarios, MWA may also offer a therapeutic option for patients presenting with multiple primary lung cancers.[4, 11] It is important to note that tumor size plays a crucial role in the success of this procedure, with studies consistently demonstrating better outcomes, including higher rates of technical success and lower incidences of local recurrence, in lesions with a maximum diameter ≤ 3 cm.[1, 2, 4, 5, 6, 11, 12, 14, 16, 17, 18, 19, 20, 21, 22, 23, 24] While some investigations have explored the application of MWA in larger tumors, extending up to 5 cm in research settings [23, 24], the current body of evidence strongly supports its use in smaller lesions for optimal results. Clinical data suggests that microwave ablation can achieve local tumor control in early-stage lung cancer patients that is comparable or slightly less to that of surgery, particularly in the subset of patients deemed medically inoperable.[1, 2, 6, 11, 16] Additionally, due to its technical characteristics, MWA may offer advantages over RFA in treating lung lesions situated near large blood vessels, as it can generate higher temperatures and is less affected by the heat dissipation caused by blood flow.[2, 4, 5, 17]
• Pulmonary Metastases: Microwave ablation is a viable consideration for patients with oligometastatic disease to the lungs, typically defined as the presence of five or fewer metastatic lesions, often with individual maximum diameters ≤ 3 cm.[5, 6, 7, 11, 12, 17, 20, 25, 26, 27, 28] These metastases may originate from a variety of primary cancers, including colorectal, sarcoma, head and neck, renal cell carcinoma, and thyroid cancers.[11] MWA may be particularly relevant when surgical removal of these lung metastases (pulmonary metastasectomy) is not a feasible option.[11] Furthermore, the procedure can potentially be integrated with or utilized following systemic therapies such as chemotherapy or immunotherapy.[4, 7, 11, 14, 16] Notably, evidence indicates that MWA for lung metastases, especially those originating from colorectal cancer, can achieve rates of local disease control and overall survival that are comparable to those obtained with surgical intervention in carefully selected patients.[6, 26, 27, 28, 29] An important benefit of MWA in the context of lung malignancies is that it represents a lung-preserving treatment option that has a minimal impact on pulmonary function. This is particularly advantageous for patients with pre-existing limitations in their respiratory reserve or those who have previously undergone lung surgeries.[7, 11, 26]

B. Hepatic Neoplasms

• Primary Hepatocellular Carcinoma (HCC): Microwave ablation is indicated for the treatment of unresectable Hepatocellular Carcinoma, particularly in patients with early-stage disease characterized by smaller tumors and well-compensated liver function (Child-Pugh class A or B).[2, 8, 30, 31, 32, 33, 34, 35, 36, 37] In specific clinical scenarios, MWA may also serve as a bridge to liver transplantation for eligible patients.[2, 35, 38] The size criteria for hepatic lesions treated with MWA generally include single tumors with a maximum diameter ≤ 5 cm, or up to three separate nodules, each measuring ≤ 3 cm.[1, 2, 8, 18, 30, 33, 37, 39] MWA can be considered as both a primary treatment for newly diagnosed HCC and as a secondary treatment option for recurrent or residual disease following other locoregional therapies.[34] Studies have demonstrated that microwave ablation can achieve long-term oncologic outcomes for HCC tumors ≤ 4 cm that are comparable to those of surgical resection, with potential benefits such as reduced intraoperative blood loss and shorter durations of postoperative hospitalization.[33] While MWA is generally best suited for patients with Child-Pugh class A or B cirrhosis, its use may be cautiously considered in highly selected Child-Pugh C patients (a relative contraindication) typically in palliative settings or as a bridge to transplant when other options are unavailable, after careful multidisciplinary risk-benefit assessment, recognizing the associated low rates of local tumor recurrence but potentially higher procedural risks.[35, 36]
• Metastatic Liver Tumors: The primary indication for microwave ablation in the treatment of metastatic liver tumors is for metastases originating from colorectal cancer, particularly in situations where surgical resection is not a feasible treatment option.[2, 3, 29, 36, 37, 39, 40] Similar to the treatment of primary liver cancer, tumor size and number are important considerations, with typical criteria including lesions with a maximum diameter ≤ 3 cm, although well-located lesions up to 5 cm may be considered. The total number of metastatic lesions treated in a single session is usually limited to five or fewer.[1, 2, 8, 18, 29, 30, 36, 37, 39, 40] Microwave ablation can also be utilized as a palliative treatment strategy to control the growth of liver metastases, alleviate associated symptoms, and potentially extend patient survival.[1, 2, 40] Clinical evidence suggests that MWA for colorectal liver metastases is a safe procedure that offers excellent local tumor control and prolonged survival in carefully selected patients when compared to historical controls.[29]

C. Thyroid Nodules and Cancers

• Benign Thyroid Nodules: Microwave ablation is indicated for the treatment of symptomatic benign thyroid nodules that cause compressive symptoms such as difficulty swallowing (dysphagia), shortness of breath (dyspnea), neck pressure, or cosmetic concerns.[3, 41, 42, 43, 44, 45, 46, 47, 48] This minimally invasive approach is particularly relevant for patients who either refuse to undergo surgical thyroidectomy or are not considered suitable candidates for surgery due to medical comorbidities.[43] Generally, the benign thyroid nodules considered for MWA are larger than 2 cm in size and are not extending significantly into the chest cavity (retrosternal extension).[41, 43, 46] Both single and multiple benign thyroid nodules can be treated with microwave ablation, although patients with multinodular goiters may require several treatment sessions over a period to achieve optimal results.[41, 43] Microwave ablation has emerged as a promising minimally invasive technique for managing benign thyroid nodules, demonstrating significant reductions in nodule volume, ranging from approximately 45.9% to 85% in various studies.[44, 45, 47, 48] This volume reduction is often accompanied by a significant improvement or complete resolution of nodule-related symptoms. Furthermore, MWA for benign thyroid nodules is associated with a low rate of complications and offers the advantage of no visible scarring on the neck.[44, 45, 47, 48] Comparative studies have indicated that microwave ablation exhibits comparable efficacy to radiofrequency ablation (RFA) in the treatment of predominantly solid benign thyroid nodules.[47] Additionally, MWA presents technical differences from RFA and laser ablation (LA) that may offer safety advantages for patients with surgical implants or pre-existing cardiac conditions.[48]
• Malignant Thyroid Nodules (Papillary Thyroid Microcarcinoma – PTMC): Microwave ablation is increasingly being recognized as a potential alternative to surgical intervention for the treatment of low-risk Papillary Thyroid Microcarcinoma, defined as papillary thyroid cancer with a maximum diameter ≤ 10 mm and confined to the thyroid gland.[45, 48, 49, 50, 51, 52] This approach is primarily considered for patients with PTMC who refuse to undergo thyroid surgery or who have medical contraindications to surgical resection.[49, 50] While primarily indicated for intrathyroidal PTMC, limited research is exploring MWA for cases with suspected minimal capsular invasion on ultrasound; however, this remains investigational due to concerns about incomplete treatment and requires careful patient selection and discussion within a multidisciplinary setting, acknowledging the lack of long-term data.[50] Clinical studies have demonstrated that microwave ablation for PTMC exhibits promising short-term efficacy that is comparable to that achieved with surgery. Notably, MWA offers advantages such as shorter operative times, reduced postoperative hospital stays, and lower overall hospitalization costs.[51] Furthermore, the rates of recurrence and lymph node metastasis following MWA for PTMC appear to be similar to those observed after surgical treatment in short-to-medium term follow-up.[51] These findings suggest that microwave ablation could represent an efficient, safe, and cost-effective therapeutic modality for carefully selected patients with papillary thyroid microcarcinoma.[51]

D. Bone Tumors and Metastases

• Bone Metastases: Microwave ablation is primarily indicated for the palliation of pain in patients with metastatic bone disease that has proven refractory to conventional treatments such as radiation therapy or systemic chemotherapy.[3, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65] In certain cases, MWA may also be utilized for achieving local control of metastatic bone tumors.[55, 56, 57] The procedure can be effectively combined with cementoplasty, a technique involving the injection of bone cement, to provide stabilization and prevent pathological fractures in bones weakened by metastatic deposits.[54, 55, 59, 61] The size of bone metastases suitable for microwave ablation is generally with a maximum diameter ≤ 5 cm.[53, 54] Clinical investigations have consistently demonstrated that MWA provides rapid and significant relief from pain associated with metastatic osseous disease. This pain reduction is often accompanied by a decrease in the patient’s reliance on analgesic medications, such as opioids, and a subsequent improvement in their overall quality of life.[54, 59, 60, 61, 62, 63, 64, 65]
• Primary Bone Tumors: Microwave ablation has shown effectiveness in the treatment of benign bone tumors, particularly osteoid osteoma, offering high rates of success, low rates of recurrence, and a minimal incidence of complications.[3, 53, 56, 57, 66] In the management of primary malignant pelvic bone tumors, MWA may play a role in limb salvage, although it is often employed as part of a comprehensive, multidisciplinary treatment strategy that includes surgical resection and chemotherapy.[67] Additionally, microwave ablation can be utilized as an intraoperative adjunct during the surgical treatment of bone tumors to effectively control intraoperative hemorrhage from the tumor or to improve the safety margins during tumor resection.[54, 56, 57] Several advantages are associated with the use of MWA for bone tumors, including its minimally invasive nature, which typically results in shorter hospital stays and less trauma to the patient. Furthermore, MWA helps in preserving the structural integrity of the bone affected by the tumor and has demonstrated the potential to stimulate an anti-tumor immune response within the patient.[53, 57]

E. Renal Neoplasms

• Small Renal Masses (Primarily Renal Cell Carcinoma – RCC): Microwave ablation is indicated for the treatment of small renal masses (SRMs), particularly presumed or biopsy-proven T1a Renal Cell Carcinoma (maximum diameter ≤ 4 cm), in patients who are not suitable candidates for surgical resection (partial or radical nephrectomy) due to significant medical comorbidities, advanced age, or presence of a solitary kidney.[Ref A, Ref B, Ref C, Ref D] It may also be considered for patients who refuse surgery or have hereditary syndromes predisposing to multiple kidney tumors (e.g., Von Hippel-Lindau disease).[Ref B, Ref E] MWA offers a nephron-sparing approach, aiming to preserve renal function, which is particularly crucial in patients with pre-existing chronic kidney disease or a solitary kidney.[Ref A, Ref D] The procedure is generally best suited for exophytic tumors (growing outwards from the kidney surface) as centrally located tumors near the renal hilum and collecting system pose higher risks of complications and incomplete ablation.[Ref C, Ref F] Clinical studies demonstrate high rates of technical success and local tumor control for appropriately selected SRMs treated with MWA, with oncologic outcomes potentially comparable to partial nephrectomy in specific patient populations, particularly those deemed unfit for surgery.[Ref A, Ref B, Ref G] Compared to Radiofrequency Ablation (RFA), MWA may achieve larger ablation zones more rapidly and be less susceptible to the heat sink effect from adjacent blood flow, potentially offering advantages for treating larger SRMs (e.g., 3-4 cm) or those near vessels.[Ref C, Ref F]

II. Brief Contraindications for Microwave Ablation

Absolute Contraindications: There are specific conditions under which microwave ablation should not be performed due to potential safety concerns. These absolute contraindications include pregnancy, as the potential risks to both the pregnant patient and the developing fetus have not been definitively established.[2, 68] Patients who have cardiac pacemakers or other types of implanted electronic medical devices are also typically not candidates for MWA, as the microwave energy could potentially interfere with the proper functioning of these devices.[2, 9, 12, 38, 68] Furthermore, the presence of an uncorrectable bleeding diathesis, indicated by abnormal coagulation indices such as an International Normalized Ratio (INR) greater than 1.5 or a platelet count below 50,000 per cubic millimeter, is an absolute contraindication due to the increased risk of significant bleeding complications.[12, 30, 36, 69, 70, 71] Finally, patients with an active infection at the intended treatment site or those with a systemic infection should not undergo microwave ablation until the infection has been adequately treated.[36, 72]

Relative Contraindications: Certain conditions may increase the risk of complications or reduce the effectiveness of microwave ablation, and therefore require careful consideration and a thorough assessment of the potential risks versus the benefits of the procedure, often involving multidisciplinary discussion. These relative contraindications include tumors located in close proximity, generally within 1 cm, to major blood vessels, vital structures (e.g., bowel, nerve plexuses), or the hepatic/renal hilum. While MWA is less susceptible to the heat sink effect than RFA, the risk of incomplete ablation and potential damage to adjacent structures still exists.[5, 12, 17, 21, 36, 37, 73, 74, 75, 76, Ref C, Ref F] Tumors that are located subcapsularly, meaning just beneath the surface of organs like the liver, lung, or kidney, may also be considered a relative contraindication due to the potential risk of organ rupture, hemorrhage, or complications such as pneumothorax (lung) or urinoma (kidney).[36, 73, 74, Ref C] Patients with a poor overall performance status, for example, those with an ECOG score greater than 2 or 3, may not be suitable candidates for MWA.[12, 36] In the context of liver tumors, involvement of the major hepatic bile ducts, significant untreated extrahepatic disease, and decompensated liver disease (Child-Pugh class C cirrhosis) are also considered relative contraindications.[36, 37] Similarly, for renal tumors, proximity to or invasion of the collecting system or major hilar vessels represents a relative contraindication.[Ref C, Ref F] Additionally, tumors that occupy a very large volume of the affected organ may limit the remaining functional reserve after ablation, making the procedure less advisable.[37] It is important to recognize that the understanding of contraindications for MWA is continually evolving as more clinical data becomes available.[38] Some contraindications that were initially based on experience with radiofrequency ablation may not strictly apply to microwave ablation due to its distinct mechanism of action and inherent technical advantages.[38] Therefore, a careful and individualized assessment is crucial in determining the appropriateness of MWA for each patient.

To provide a quick reference for our colleagues, the following table summarizes the general contraindications for microwave ablation as discussed above:

Absolute Contraindications	Relative Contraindications
Pregnancy	Tumors in close proximity (< 1 cm) to major blood vessels, vital structures (bowel, nerve), or hepatic/renal hilum
Cardiac pacemakers or other implanted electronic devices	Subcapsularly located tumors (liver, lung, kidney)
Uncorrectable bleeding diathesis (INR >1.5, Plt <50k)	Poor patient performance status (e.g., ECOG > 2 or 3)
Active infection (local site or systemic)	Tumors involving major hepatic bile ducts or renal collecting system
	Ascites (particularly for liver ablation)
	Significant untreated extrahepatic disease (context-dependent, e.g., liver/renal ablation)
	Decompensated liver disease (e.g., Child-Pugh class C cirrhosis)
	Tumors occupying a very large volume of the organ, limiting functional reserve
	Central/hilar renal tumors

III. Conclusion

The Radiology Department at the National Cancer Center Benghazi remains dedicated to providing advanced and comprehensive cancer care to our patients. The introduction of the microwave ablation service represents a significant step forward in our ability to offer minimally invasive treatment options for a wide array of oncological conditions affecting the lung, liver, kidney, thyroid, and bone, as well as for symptomatic benign thyroid nodules. This technology offers a valuable addition to our therapeutic armamentarium, with the potential for effective local tumor control, pain palliation, and symptom relief in appropriately selected patients discussed within a multidisciplinary team setting. We encourage our colleagues to consider the microwave ablation service as a vital treatment modality, recognizing its minimally invasive nature, its demonstrated efficacy in various clinical scenarios, and its potential advantages over other ablation techniques.

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IV. Contact Information

For further inquiries regarding the new Microwave Ablation service, including patient selection criteria, referral processes, or to discuss potential cases, please do not hesitate to contact :

• Dr. Seraj Alsaifi
• Phone: +218925302032
• Email: Seraj.alsaifi@nccb.ly