Value of Percutaneous Microwave Ablation as an Effective Treatment for Hepatocellular Carcinoma

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1 Med. J. Cairo Univ., Vol. 82, No. 2, June: , Value of Percutaneous Microwave Ablation as an Effective Treatment for Hepatocellular Carcinoma ENAS A.R. ALKAREEMY, M.D.*; HUSSEIN ELAMIN, M.D.*; OSAMA M. HETTA, M.D.**; LOBNA ABDEL WAHID, M.D.*; WAEL A. ABBAS, M.D.* and AHMED M.M. ASHMAWY, M.Sc.* The Departments of Internal Medicine* and Radiology**, Faculties of Medicine, Assuit* and Ain Shams** Universities Abstract Background: Hepatocelluar carcinoma (HCC) is the fifth most common malignant disease and the third most common cause of cancer death worldwide. Egypt has the highest prevalence of HCV in the world and up to 90% of HCC cases in the Egyptian population were due to HCV. Currently, minimal invasive techniques have become available for local destruction of hepatic tumors. Microwave ablation (MW) is one of the common thermal ablation therapies for treatment of HCC. Aim of the Study: Evaluation of therapeutic efficacy and safety of MW thermal ablation for treatment of HCC. Patients and Methods: 30 patients with HCC from Assuit and Ain Shams University Hospitals were enrolled in the study. All patients underwent MW ablation of the hepatic lesion and follow-up CT abdomen was done 30 days later to assess the efficacy and detect the complications of MW ablation. Results: After 30 days, complete tumor necrosis was achieved in 27 patients (90%). Both increased lesion size and advanced Child class were found to be associated with worse outcome and recurrence. Conclusions: Microwave ablation is safe and effective technique and has a promising potential in the treatment of hepatocellular carcinoma. Key Words: Hepatocellular carcinoma Microwave ablation. Introduction HEPATOCELLULAR carcinoma is the fifth most common malignant disease and the third most common cause of cancer death worldwide [1]. In Egypt, HCC was reported to account for about 4.7% of chronic liver disease patients [2]. Hepatocellular carcinoma usually develops following chronic liver inflammation caused by hepatitis C (HCV) or B (HBV) virus [3]. Egypt has the highest prevalence of HCV in the world and Correspondence to: Dr. Enas A.R. Alkareemy, The Department of Internal Medicine, Assuit University up to 90% of HCC cases in the Egyptian population were due to HCV [4]. Majority of patients suffering from HCC are not candidates for surgery because of underlying cirrhosis, multiple tumors and recurrent tumors. Currently, minimal invasive techniques have become available for local destruction of hepatic tumors [5,6]. The common energy sources include radiofrequency (RF), microwave (MW), or laser. These techniques have yielded promising clinical results [5] and the survival rates compare favorably with those of hepatectomy [7]. Recently, there has been continued interest in the clinical application of MW ablation [8,9]. MW ablation is one of the common thermal ablation therapies for treatment of liver malignancies [10]. MW ablation refers to the use of all electromagnetic methods for inducing tumor destruction by using devices with frequencies of at least 900 MHz [11]. Microwave ablation offers many of the benefits of radiofrequency ablation and has several other theoretical advantages that may increase its effectiveness in the treatment of tumors. The potential benefits of MW technology include consistently higher intratumoral temperatures, larger tumor ablation volumes, faster ablation times, ability to use multiple applicators, improved convection profile, optimal heating of cystic masses, and less procedural pain [11,12]. In addition, microwave ablation does not require the placement of grounding pads [13]. However, traditional non cooled-shaft microwave antennae are subjected to high power feedback, so the shaft temperature becomes high, which may cause skin burning at the point of antenna entry [11,14]. The cooled-shaft microwave antenna can effectively prevent shaft overheating [15]. Consequently, it is possible to increase the power output to enlarge the volume of coagulation while, at the same time, avoiding skin injury [16]. 197

2 198 Value of Percutaneous Microwave Ablation as an Effective Treatment The purpose of our study was to evaluate the therapeutic effectiveness of percutaneous MW coagulation therapy and the rate of complete ablation using cooled-shaft antenna for the treatment of unresectable HCC. Patients and Methods 30 patients with HCC from Assuit and Ain Shams University Hospitals, who deemed unsuitable for hepatic resection, were referred to interventional radiology department at Ain Shams University Hospital during the period between November 2011 and April Diagnosis of HCC was settled by typical triphasic spiral computed tomography (CT) criteria of HCC and/or significant elevation of a-fetoprotein >200gg/L. The inclusion criteria were as follows: Patients with HCC who are unsuitable or refused partial hepatectomy. No more than 4 tumors with at least 1 tumor. Size measuring between 1 cm to 7cm in maximum dimension. Absence of vascular invasion or lymph node involvement. Liver function status at Child-Pugh A or B. Platelet count >50x10 9 /L. The exclusion criteria include: Age older than 75 years or younger than 18 years old. Evidence of extra-hepatic metastases. More than five intra-hepatic nodules. Presence of vascular or lymph node involvement. Severe bleeding diathesis (INR >1.5). A written consent was taken from every participant. The details of the procedure of thermal ablation was explained to them. All the study patients were subjected to the followings: 1- Standard pre-operative evaluation of patients including a triple phase computed tomography (CT) scan of the abdomen and pelvis. 2- Abdominal ultrasound. 3- Laboratory investigations including; liver enzymes (SGOT, SGPT), serum albumin, coagulation profile (PT, PTT, INR), serum creatinine and complete blood picture. 4- Ablation procedure: Microwave ablation was performed with the use of short-acting IV anesthesia Propofol (Diprivan, Zeneca Pharmaceuticals). Microwave ablation was performed percutaneously under real-time ultrasound guidance using a GE LOGIQ 7 Pro US scanner (USA) with a 3.5-5MHz probe. MW ablation was performed using an HS AMICA microwave delivery system (HS Hospital service S.P.A Roma, Italy). This microwave delivery system operates at frequency of 2450 MHz and a power output up to 100W. A 14 gauge (either 150mm or 200mm) cooled shaft electrode named AMICA-probe to deliver MW energy into liver tissue. Before treatment began, a detailed plan for the placement of the electrode, the power output setting, and the emission time was established on a tumor-by-tumor basis with the aim to completely destroy the tumor, as well as the surrounding cm normal appearing liver tissue. Through a small incision of the skin a guide needle with a sheath was inserted and positioned at targeted tumor under sonographic guidance. Then the microwave electrode was introduced and the sheath was withdrawn approximately 4-5cm while keeping the electrode needle at its place to ensure that a portion of at least 4cm from the tip of the electrode was exposed. Being connected to the microwave generator, the energy application was then started. In general a high power for a short time was used, i.e., an output setting of 60W for 300s. For some tumors, a prolonged application ( s) of energy 60W was used. In lesions >3cm, the needle can be moved a bit backward, change direction of insertion into the tumor, and start a further treatment session. This maneuver was repeated according to the size of the lesion. This ensues a bigger dimension of necrosis than applying the microwaves for the maximum time, since during the last 5-10min., the dimension of necrosis increases very slowly. During each application of microwave energy, an expanding hyperechogenic area was produced. These changes are visible on sonographic images but diminished rapidly as soon as the microwave generator was switched off and completely disappeared within 8 hours.

3 Enas A.R. Alkareemy, et al. 199 To minimize tumor seeding, the needle track was routinely ablated while withdrawing the antenna at about 2cm/s. The power was seated at 40W. 5- Assessment of therapeutic efficacy: Local therapeutic efficacy was evaluated by: Contrast enhanced dynamic CT scanning at 30 days after treatment: Complete ablation was defined as uniform hypo-attenuation without enhancement in the previous tumor area [17,18]. Technical success was defined as complete ablation of the tumor, as determined at CT performed one month after MW ablation [19]. Serum α -fetoprotein level was checked at 30 days after MW ablation. 6- Statistical analysis of the data was performed by using SPSS version 16 software package. Categorical data parameters were presented in the form of frequency and percent. Comparison was performed by Chi-square test for categorical data. Quantitative data were expressed in the form of mean and SD. Mann-Whitney test and Paired sample t-test were used to test the significance among groups for quantitative data. Probability level ( p- value) was assumed significant if less than Results This prospective study includes 30 cirrhotic patients with HCC. A total of 35 nodules were ablated using microwave energy. Table (1) shows the baseline characteristics of all patients. Table (1): Demographic, clinical and laboratory parameters of the study group. Parameter % Sex; male (%) 28 (93.3%) Age (Mean±SD) 57.5±7.5 Smoking (%) 9 (30%) Diabetes mellitus (%) 5 (16.7%) HBV (%) 1 (6.7%) HCV (%) 29 (93.3%) Child-Pugh class: A 23 (76.7%) B 7 (23.3%) Encephalopathy (%) 0 (0%) Ascites (%) 3 (10%) Albumin (g/dl) 3.25±0.47 Bilirubin (mg/dl) 1.58±0.84 PT (sec) 15.1±2.64 INR 1.27±0.17 ALT (U/L) 46.6±28.8 AST (U/L) 66.4±29.4 Hb (gm/dl) 13± 1.14 TLC (x10 3 ll -1 ) 5.29± 1.85 PLT (x10 3 ll -1 ) ±50.4 α-fetoprotein 235.8±581 Table (2) shows lesions characteristic. Table (2): Characteristics of the hepatic focal lesion. Parameter No. of nodules: Single 25 (83.3%) Multiple 5 (16.7%) Diameter of nodules: <3cm 15 (43.3%) 3 to 5cm 14 (40%) >5cm 6 (16.7%) Size (cm) (Mean±SD) 3.4±0.9 Site of nodules: Subcapsular 11 (31.4%) Contact to vessels 8 (22.9%) Contact to gall bladder 1 (2.9%) Contact to intestine 1 (2.9%) Others 14 (40%) Follow-up abdominal CT were done in all patients after 30 days. Complete tumor necrosis was achieved in 27 patients (90%) while incomplete ablation were observed in 3 patients (10%). Two patients with incomplete ablation were treated by another session of MW ablation and one patient underwent complimentary chemoembolization. Figure (1) shows HCC 4x4cm in segment VI with pretreatment contrast enhanced scan, and 1 month after MW ablation depicts a non-enhancing hypoattenuating area with evident safety margin indicating complete ablation. Table (3) shows number of MW ablation sessions and results. Table (3): Number of MW ablation sessions and results. Parameter No. of sessions: Single 28 (93.3%) Two 2 (6.7%) MW ablation: Complete 27 (90%) Incomplete 3 (10%) Alpha-fetoprotein ( α-fp) was measured for all patients preoperatively, mean α-fp was ±581 µg/l. However, at the follow-up visit, only patients with values more than 200µg/L (6 patients, 20%) were followed-up with serum α -FP assay. They showed decreased level to within the normal range one month after ablation (mean ±238µg/L), p-value While those with preoperative α - FP serum level less than 200µg/L (n=24) were only evaluated by CT examination. % %

4 200 Value of Percutaneous Microwave Ablation as an Effective Treatment A- (Arterial phase) pre ablation shows arterial enhancement. A- (Venous phase) pre ablation shows venous washout. Fig. (1): A 62-year-old male with hepatocellular carcinoma. A- Pretreatment contrast enhanced scan reveals a 4x4cm enhancing HCC in segment VI. B- Scan obtained 1 month after PMCT depicts a non-enhancing hypoattenuating area with evident safety margin indicating complete ablation. Tumor size and child class were found to be significantly related to successful MW ablation. While tumor site was non significant for complete ablation Table (4). Table (4): Factors affecting the effect of MW ablation. Parameter Size of the nodules *: <3cm 3 to 5cm >5cm Site of the nodules *: Subcapsular Contact to vessels Contact to gall bladder Contact to intestine Any site (Other) Child Pugh+: A B 14 (40%) 14 (40%) 4 (11.4%) MW ablation Complete Incomplete 10 (28.5%) 7 (20%) 1 (2.9%) 1 (2.9%) 13 (37%) 22 (73.3%) 5 (16.7%) 1 (2.9%) 0 2 (5.7%) p value 0.04 daysaftertheablation.feverwasobservedin10 patients(30%)andcontinuedforupto3days.small subcapsularhematomawasobservedonusexaminationinonepatientand one patient with arteriovenous fistula in the periportal area (6%). Discussion Various locoregional therapies are used for patients who are not candidates for surgical cure because of severity of liver disease or advanced stage of HCC [20]. 1(2.9%) 0.98 The tumors are destroyed in situ either by direct 1(2.9%) chemical application (ethanol ablation) or by cool- 0 ing (cryotherapy) or by heating (radiofrequency 0 1(2.9%) or microwave ablation) [21]. Currently, RF ablation is considered the treatment of choice for patients 1(3.3%) 0.05 with HCC or metastases that are not amenable to 2 (6.7%) open surgery or laparoscopic treatment [22-29]. * : Total number of nodules = 35 nodule. + : Total number of patients = 30 patients. No major complications occurred in our study group.local pain, varying from mild to severe, was experienced by in the upper part of the abdomen in 15 patients (50%) and usually resolved within 3-4 Microwave ablation offers many of the benefits of RF ablation and has several other theoretical advantages that may increase its effectiveness in the treatment of tumors. The potential benefits of microwave technology include consistently higher intratumoral temperatures, larger tumor ablation

5 Enas A.R. Alkareemy, et al. 201 volumes, faster ablation times, ability to use multiple applicators, improved convection profile, optimal heating of cystic masses, and less procedural pain [12,30]. In addition, microwave ablation does not require the placement of grounding pads [13]. Microwave energy can ablate tissues around large hepatic vessels as large as 1 0mm and creates larger zones of ablation in high-perfusion areas [31,28]. In this study, a cooled-shaft antenna was used. It has two channels inside the shaft lumen with distilled water circulated by a peristaltic pump to continuously cool the shaft. The low antenna shaft temperature can deliver more energy into the tissue without causing skin burn. In addition, low antenna shaft temperature can reduce higher temperature in the center to decrease tissue charring and improve energy transfer [32]. As result, the ablation zone can be remarkably expanded. In the present study the ablation procedure was performed percutaneously. Microwave ablation was performed for 30 patients having 35 nodules of HCC using the cooled-shaft antenna. 27 of 30 patients (90%) achieved complete ablation, which is considered acceptable. The complete ablation rates for tumors 3cm or less were 94% (14 of 15 nodules), 3 to 5cm was 100% (14 of 14 nodules) and those larger than 5cm were 67% (4 of 6 nodules) respectively. The complete ablation rate in patients with tumors measuring less than 5 cm was significantly higher than in patients with tumors measuring more than 5cm. The complete response was decreased to 67% in tumors larger than 5cm and this can be explained by possibility of the presence of micro-satellite around the tumor and the increase in the incidence of vascular invasion with the increase in the tumor size. Also, this may be partially attributed to increased fibrous septa inside the tumor with the increase in tumor size. Lu et al., [19] reported a technical success rates for tumors 2cm or smaller and those larger than 2cm were 98% (45 of 46 nodules) and 92% (56 of 61 nodules), respectively, and after additional MW ablation sessions technical success was achieved in all incompletely ablated tumors. Kuang et al., [9] treated 90 patients with unresectable liver cancers, the complete ablation rates were 94% for small (less than 3cm), 91% for intermediate ( cm), and 92% for large ( cm) liver cancers. When comparing between the above two studies and our current series, the results of our study are lower which may be attributed to our small sample size that limits the validity of the statistical results. There are many factors affecting the complete ablation of HCC including the size of the tumor and Child class. The complete ablation is readily achieved with lesions less than 5cm and/or with child A than child B [9]. Liang et al., reported that smaller tumors were more easily destroyed than larger tumors during microwave ablation. Child- Pugh classification, tumor size, and number of tumors were identified as significant independent prognostic factors. They concluded that there is a significantly higher probability of long-term survival after MWA treatment for patients with a single tumor of 4.0cm or less and Child-Pugh class A cirrhosis [5]. In concordance with the above, the present study concluded that small tumor size and Child class A were readily prone to complete ablation. In our study, 6 patients with elevated AFP before ablation showed decreased levels to within the normal range one month after ablation. The only 6 (20%) patients with increase AFP before ablation indicating that elevated AFP is not conclusive in diagnosis of HCC and the diagnosis depends mainly on CT imaging with criteria of HCC, but there is significant difference between the AFP pre and post MWA. Local pain, fever and mild subcapsular hematoma (observed on US examination) in minority of patients. These were spontaneously resolved with no need for treatment. No major complications related to the ablation procedure itself except one patient with arteriovenous fistula at priportal area. Some studies of alternative ablative modalities have reported complications in up to 33% of the patients treated [33,34]. Also, the study of Xu et al., reported complications related to MW ablation in nine patients including pleural effusion, liver failure, hepatic abscess, skin burn and subcapsular hematoma [35]. No tumor seeding was observed in our study. This could be explained by two reasons; the first is cauterization of the needle track for 10 seconds when the antenna was withdrawn and the second is avoiding pre-procedural biopsy. This was in concordance with Liang et al., who reported that performance of biopsy before ablation may be the main reason for tumor seeding in their series of patients [36]. Liu et al., [39] reported one patient experienced subcutaneous tumor seeding of needle track one month after MW ablation.

6 202 Value of Percutaneous Microwave Ablation as an Effective Treatment Limitation of the study: The number of patients in this study was relatively small. Larger sample sizes are required to document the benefits of MW ablation in the treatment of large HCC tumors. The follow-up was only short term, hence reliable long term results and survival rates could not be evaluated. Conclusion: Microwave ablation with a cooled-shaft antenna enabled greater delivery of microwave energy producing a larger ablation zone in one application of energy within a short duration and at the same time avoiding skin injury. Thus microwave ablation is safe and effective technique and has a promising potential in the treatment of hepatocellular carcinoma. References 1- PARKIN D.M., BRAY F., FERLAY J. and PISANI P.: Global cancer statistics, CA Cancer J. 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