Local tumor progression patterns after radiofrequency ablation of colorectal cancer liver metastases

PURPOSE:We aimed to evaluate patterns of local tumor progression (LTP) after radiofrequency ablation (RF ablation) of colorectal cancer liver metastases (CRCLM) and to highlight the percentage of LTP not attributable to lesion size or RF ablation procedure-related factors (heat sink or insufficient ablation margin).METHODS:CRCLM treated by RF ablation at a single tertiary care center from 2004–2012, with a minimum of six months of postprocedure follow-up, were included in this retrospective study. LTP morphology was classified as focal nodular (270°), or crescentic (90°–270°). Initial metastasis size, minimum ablation margin size, morphology of LTP, presence of a heat sink, and time to progression were recorded independently by two radiologists.RESULTS:Thirty-two of 127 RF ablation treated metastases (25%) with a mean size of 23 mm (standard deviation 12 mm) exhibited LTP. Fifteen of 32 LTPs (47%) were classified as focal nodular, with seven having no procedure-related factor to explain recurrence. Ten of 32 LTPs (31%) were circumferential, with four having no procedure-related factor to explain recurrence. Seven of 32 LTPs (22%) were crescentic, with two having no procedure-related factor to explain recurrence. Of the 13 lesions without any obvious procedure-related reason for LTP, six (46%) were <3 cm in size.CONCLUSION:Although LTP in RF ablation treated CRCLM can often be explained by procedure-related factors or size of the lesion, in this study up to six (5%) of the CRCLM we treated showed LTP without any reasonable cause

TRATTAMENTO ABLATIVO CON MICROONDE DI METASTASI EPATICHE DA TUMORE DELLA MAMMELLA: STUDIO DI FATTIBILITÀ ED EFFICACIA

INTRODUCTION Prognosis of patients with breast cancer liver metastases is still dismal. Some retrospective data support adjuvant surgery in selected patients. Ablative treatment in the management of breast cancer liver metastases remains controversial. MATERIAL AND METHODS We evaluated the efficacy (complete ablation and recurrence rate) and the safety (morbidity and mortality) of the microwave ablation treatment (MWA) of breast cancer liver metastases, performed in our Center from 2009 to 2016. Analysis was performed on a nodule-oriented and patient-oriented base. RESULTS Median time to liver metastases development was 52.13 months (IQR 25.5- 81.72), 92.5% of which were metachronous. Forty patients underwent 51 MWA sessions, percutaneously (27 sessions, 33 nodules) and laparoscopically (24 sessions, 67 nodules). Complete ablation rate for nodules ≤2 cm was 95.56% whereas the 3- and 6-months recurrence rate, irrespectively of the nodule dimension, was 12.73% and 26.19%, respectively. MWA was associated with no 90-day mortality. Morbidity rate was 20%. Two patients are alive and free of disease at 49 and 86 months, respectively

Thermal ablation of biological tissues in disease treatment: A review of computational models and future directions

Percutaneous thermal ablation has proved to be an effective modality for treating both benign and malignant tumors in various tissues. Among these modalities, radiofrequency ablation (RFA) is the most promising and widely adopted approach that has been extensively studied in the past decades. Microwave ablation (MWA) is a newly emerging modality that is gaining rapid momentum due to its capability of inducing rapid heating and attaining larger ablation volumes, and its lesser susceptibility to the heat sink effects as compared to RFA. Although the goal of both these therapies is to attain cell death in the target tissue by virtue of heating above 50 oC, their underlying mechanism of action and principles greatly differs. Computational modelling is a powerful tool for studying the effect of electromagnetic interactions within the biological tissues and predicting the treatment outcomes during thermal ablative therapies. Such a priori estimation can assist the clinical practitioners during treatment planning with the goal of attaining successful tumor destruction and preservation of the surrounding healthy tissue and critical structures. This review provides current state-of- the-art developments and associated challenges in the computational modelling of thermal ablative techniques, viz., RFA and MWA, as well as touch upon several promising avenues in the modelling of laser ablation, nanoparticles assisted magnetic hyperthermia and non- invasive RFA. The application of RFA in pain relief has been extensively reviewed from modelling point of view. Additionally, future directions have also been provided to improve these models for their successful translation and integration into the hospital work flow

Three-dimensional quantification of the vascular cooling effect of hepatic vessels during high-energy microwave ablation ex vivo

EINLEITUNG: Die Mikrowellenablation (MWA) ist ein thermoablatives Verfahren, das in der Behandlung von Lebertumoren zunehmend an Bedeutung gewinnt. Kühleffekte durch lebereigene Gefäße beeinflussen den Ablationserfolg jedoch maßgeblich. Problematisch dabei ist, dass der Kühleffekt zu einer unvollständigen Tumordestruktion und folglich zu Tumorrezidiven führen kann. Ziel dieser Arbeit war es, den vaskulären Kühleffekt bei der MWA anhand eines dreidimensionalen Ex-vivo-Modells zu evaluieren. MATERIAL UND METHODEN: Es wurden MWA an Ex-vivo-Schweinelebern durchgeführt. Zur Simulation eines Gefäßflusses wurde eine mit Wasser perfundierte Glasröhre in die Leber eingeführt. Anschließend erfolgten die Ablationen bei verschiedenen Antennen-Gefäß-Abständen (2,5; 5; 10 mm) und Flussraten (0, 1, 2, 5, 10, 100, 500 ml/min) für jeweils fünf Minuten mit einer zugeführten Gesamtenergie von 100 W. Die Ablationen wurden im Anschluss bei –80 °C eingefroren, am Kryostat geschnitten und alle 2 mm fotografiert. Anhand dieser makroskopischen Bildreihen erfolgte eine dreidimensionale, qualitative und quantitative Analyse der Ablationen unter Berücksichtigung der Kühleffekte. ERGEBNISSE: Insgesamt wurden 132 MWA in 22 Versuchsreihen durchgeführt. Bei allen Versuchsreihen mit einer Gefäßflussrate ≥ 2 ml/min traten Kühleffekte auf und es wurde eine geringe, bis stark ausgeprägte Veränderung der Ablationsform beobachtet. Bei einem Antennen-Gefäß-Abstand von 2,5 mm zeigten sich bei Ablationen mit Flussraten bis zu 10 ml/min keine Kühleffekte im Ablationszentrum, allerdings traten diese in der Ablationsperipherie auf. Betrug der Antennen-Gefäß-Abstand 5 und 10 mm, so waren Kühleffekte in der gesamten Ablation, insbesondere in den zentralen Bereichen, zu beobachten. Ohne einen Kühlfluss konnten mit der MWA bei 100 W und fünf Minuten Ablationsgrößen bis zu 16 mm zuverlässig erreicht werden. Bei Vorhandensein eines Kühlflusses führten vaskuläre Kühleffekte allerdings zu einer Verringerung der Ablationsgröße um bis zu 56 %. SCHLUSSFOLGERUNG: Bei der MWA von Lebergewebe können bei Vorhandensein größerer Blutgefäße relevante Kühleffekte entstehen. Diese sind in Abhängigkeit von der Flussrate und dem Antennen-Gefäß-Abstand in verschiedenen Ablationsbereichen unterschiedlich stark ausgeprägt. In der Klinik sollten im Rahmen der Ablationsplanung Kühleffekte beachtet werden, da diese bereits bei geringen Flussraten zu relevanten Änderungen der Ablationsform führen können.INTRODUCTION: Microwave ablation (MWA) is a thermoablative procedure that is becoming increasingly important in the treatment of liver tumors. However, vascular cooling effects induced by hepatic vessels significantly influence the ablation success. Especially problematic is, that the cooling effect may lead to incomplete tumor destruction and consequently to tumor recurrence. The aim of this work was to evaluate the vascular cooling effect in MWA using a three-dimensional ex vivo model. MATERIAL AND METHODS: MWA was performed in ex vivo porcine livers. A glass tube perfused with water was inserted into the liver to simulate a vascular flow. Ablations were performed at various antenna-vessel-distances (2.5, 5, 10 mm) and flow rates (0, 1, 2, 5, 10, 100, 500 ml/min) for five minutes each with a total applied energy of 100 W. Afterwards the ablations were frozen at –80 °C, sectioned at the cryostat and photographed every 2 mm. Using these macroscopic image series, a three-dimensional, a qualitative and a quantitative analysis of the ablations were performed, taking into account the cooling effects. RESULTS: A total of 132 MWAs in 22 test series were performed. Cooling effects occurred in all test series with a vessel flow rate ≥ 2 ml/min and a mild to severe change in ablation shape was observed. At an antenna-vessel-distance of 2.5 mm, no cooling effects occurred in the ablation center for ablations with flow rates up to 10 ml/min, however some occurred in the ablation periphery. If the antenna-vessel-distance was 5 mm and 10 mm, cooling effects were observed throughout the ablation, especially in the central ablation areas. Without a vascular flow, ablations up to 16 mm could be reliably achieved with the MWA at 100 W and five minutes. However, in the presence of a vascular flow, vascular cooling effects resulted in a reduction in ablation size of up to 56%. CONCLUSION: Relevant cooling effects can occur during MWA of liver tissue in the pres- ence of larger blood vessels. Cooling effects vary in severity in different ablation areas depending on the flow rate and the antenna-vessel-distance. In the clinical setting, cooling effects should be considered as part of ablation planning, as these can lead to relevant changes in ablations shape even at low flow rates