Microwave ablation for colorectal cancer metastasis to the liver: a single-center retrospective analysis.

BACKGROUND: The purpose of this study is to evaluate the safety and intermediate-term efficacy of percutaneous microwave (MW) ablation for the treatment of colorectal liver metastases (CRLM) at a single institution. METHODS: A retrospective review was performed of all CRLM treated with MW ablation from 3/2011 to 7/2020 (102 tumors; 72 procedures; 57 patients). Mean age was 60 years (range, 36-88) and mean tumor size was 1.8 cm (range, 0.5-5.0 cm). The patient population included 19 patients with extra-hepatic disease. Chemotherapy (pre- and/or post-ablation) was given in 98% of patients. Forty-five sessions were preceded by other focal CRLM treatments including resection, ablation, radiation, and radioembolization. Kaplan-Meier curves were used to estimate local tumor progression-free survival (LTPFS), disease-free survival (DFS), and overall survival (OS) and multivariate analysis (Cox Proportional Hazards model) was used to test predictors of OS. RESULTS: Technical success (complete ablation) was 100% and median follow-up was 42 months (range, 1-112). There was a 4% major complication rate and an overall complication rate of 8%. Local tumor progression (LTP) rate during the entire study period was 4/98 (4%), in which 2 were retreated with MW ablation for a secondary LTP-rate of 2%. LTP-free survival at 1, 3, and 5 years was 93%, 58%, and 39% and median LTP-free survival was 48 months. OS at 1, 3, and 5 years was 96%, 66%, 47% and median OS was 52 months. There were no statistically significant predictors of OS. CONCLUSIONS: MW ablation of hepatic colorectal liver metastases appears safe with excellent local tumor control and prolonged survival compared to historical controls in selected patients. Further comparative studies with other local treatment strategies appear indicated.

Differential Imaging of Liver Tumors before and after Microwave Ablation with Electrode Displacement Elastography.

Liver cancer is a leading cause of cancer-related deaths; however, primary treatment options such as surgical resection and liver transplant may not be viable for many patients. Minimally invasive image-guided microwave ablation (MWA) provides a locally effective treatment option for these patients with an impact comparable to that of surgery for both cancer-specific and overall survival. MWA efficacy is correlated with accurate image guidance; however, conventional modalities such as B-mode ultrasound and computed tomography have limitations. Alternatively, ultrasound elastography has been used to demarcate post-ablation zones, yet has limitations for pre-ablation visualization because of variability in strain contrast between cancer types. This study attempted to characterize both pre-ablation tumors and post-ablation zones using electrode displacement elastography (EDE) for 13 patients with hepatocellular carcinoma or liver metastasis. Typically, MWA ablation margins of 0.5-1.0 cm are desired, which are strongly correlated with treatment efficacy. Our results revealed an average estimated ablation margin inner quartile range of 0.54-1.21 cm with a median value of 0.84 cm. These treatment margins lie within or above the targeted ablative margin, indicating the potential to use EDE for differentiating index tumors and ablated zones during clinical ablations. We also obtained a high correlation between corresponding segmented cross-sectional areas from contrast-enhanced computed tomography, the current clinical gold standard, when compared with EDE strain images, with r2 values of 0.97 and 0.98 for pre- and post-ablation regions.

Comparison of Displacement Tracking Algorithms for in Vivo Electrode Displacement Elastography.

Hepatocellular carcinoma and liver metastases are common hepatic malignancies presenting with high mortality rates. Minimally invasive microwave ablation (MWA) yields high success rates similar to surgical resection. However, MWA procedures require accurate image guidance during the procedure and for post-procedure assessments. Ultrasound electrode displacement elastography (EDE) has demonstrated utility for non-ionizing imaging of regions of thermal necrosis created with MWA in the ablation suite. Three strategies for displacement vector tracking and strain tensor estimation, namely coupled subsample displacement estimation (CSDE), a multilevel 2-D normalized cross-correlation method, and quality-guided displacement tracking (QGDT) have previously shown accurate estimations for EDE. This paper reports on a qualitative and quantitative comparison of these three algorithms over 79 patients after an MWA procedure. Qualitatively, CSDE presents sharply delineated, clean ablated regions with low noise except for the distal boundary of the ablated region. Multilevel and QGDT contain more visible noise artifacts, but delineation is seen over the entire ablated region. Quantitative comparison indicates CSDE with more consistent mean and standard deviations of region of interest within the mass of strain tensor magnitudes and higher contrast, while Multilevel and QGDT provide higher CNR. This fact along with highest success rates of 89% and 79% on axial and lateral strain tensor images for visualization of thermal necrosis using the Multilevel approach leads to it being the best choice in a clinical setting. All methods, however, provide consistent and reproducible delineation for EDE in the ablation suite.

Post-Procedure Evaluation of Microwave Ablations of Hepatocellular Carcinomas Using Electrode Displacement Elastography.

Microwave ablation has been used clinically as an alternative to surgical resection. However, lack of real-time imaging to assess treated regions may compromise treatment outcomes. We previously introduced electrode displacement elastography (EDE) for strain imaging and verified its feasibility in vivo on porcine animal models. In this study, we evaluated EDE on 44 patients diagnosed with hepatocellular carcinoma, treated using microwave ablation. The ablated region was identified on EDE images for 40 of the 44 patients. Ablation areas averaged 13.38 ± 4.99 cm2 on EDE, compared with 7.61 ± 3.21 cm2 on B-mode imaging. Contrast and contrast-to-noise ratios obtained with EDE were 232% and 98%, respectively, significantly higher than values measured on B-mode images (p < 0.001). This study indicates that EDE is feasible in patients and provides improved visualization of the ablation zone compared with B-mode ultrasound.

Percutaneous microwave ablation of hepatocellular carcinoma with a gas-cooled system: initial clinical results with 107 tumors.

PURPOSE: To retrospectively review the results of hepatocellular carcinoma (HCC) treatment with a high-power, gas-cooled, multiantenna-capable microwave device. MATERIALS AND METHODS: A total of 107 HCCs in 75 patients (65 men) with a mean age of 61 years (range, 44-82 y) were treated via percutaneous approach. Combination microwave ablation and transarterial chemoembolization was performed for 22 tumors in 19 patients with tumors larger than 4 cm (n = 10), tumors larger than 3 cm with ill-defined margins (n = 7), or lesions not identified with ultrasonography (n = 5). Mean tumor size was 2.1 cm (range, 0.5-4.2 cm), with median follow-up of 14 months, for ablation alone; compared with 3.7 cm (range, 1.0-7.0 cm) and 12 months, respectively, for combination therapy. All procedures were performed with a single microwave system (Certus 140) with one to three 17-gauge antennas. RESULTS: Mean ablation time was 5.3 minutes (range, 1-11.5 min). All treatments were considered technically successful in a single session. Primary technique effectiveness rates were 91.6% (98 of 107) overall, 93.7% (89 of 95) for tumors 4 cm or smaller, and 75.0% (nine of 12) for tumors larger than 4 cm; and 91.8% (78 of 85) for ablation alone and 90.9% (20 of 22) for combination therapy. There was no major complication or procedure-related mortality. The overall survival rate was 76.0% at a median 14-month clinical follow-up, with most deaths related to end-stage liver disease (n = 11) or multifocal HCC (n = 5). CONCLUSIONS: Treating HCC with a gas-cooled, multiantenna-capable microwave ablation device is safe, with promising treatment effectiveness.

High-powered microwave ablation of t1a renal cell carcinoma: safety and initial clinical evaluation.

PURPOSE: Percutaneous radiofrequency ablation and cryoablation are accepted alternative treatments for small renal cell carcinomas (RCC) in high-risk patients. The recent development of high-powered microwave (MW) ablation offers theoretical advantages over existing ablation systems, including higher tissue temperatures, more reproducible ablation zones, and shorter procedural times. The purpose of this study is to review the feasibility, safety, and early efficacy of a novel high-powered percutaneous MW ablation system to treat RCC. METHODS: An institutional database identified 53 consecutive patients with biopsy-proven RCC ≤4 cm (55 tumors) who were treated with percutaneous MW ablation using a novel MW ablation system. All patients had percutaneous renal mass biopsy, which identified RCC before ablation. Postprocedure follow-up imaging was performed by contrast-enhanced computed tomography or magnetic resonance imaging. RESULTS: Mean patient age was 66 years and 81% of patients were male. RCC subtypes included clear cell (n=25), papillary (n=12), and unspecified (n=18) and Fuhrman grades 1, 2, 3, and ungraded in 15, 25, 1, and 14 patients, respectively. The mean tumor diameter was 2.6 cm (range 0.8-4.0 cm). Six low-grade complications were recorded during 53 (11.3%) procedures: five Clavien Grade 1 (urine retention, fluid overload, and atrial fibrillation) and one Grade 2 (hemorrhage requiring transfusion). The postprocedure estimated glomerular filtration rate was not significantly changed from preprocedure levels (median: -1.1%, p=0.10). Median follow-up was 8 months (interquartile range [IQR] 5-18.25) with 0/38 (0%) patients demonstrating evidence of local recurrence or metastasis during surveillance imaging. CONCLUSIONS: Use of a high-powered MW ablation system for the treatment of T1a RCC is feasible, safe, and efficacious with short-term follow-up. A longer follow-up is warranted to evaluate oncologic outcomes.