Microwave ablation: an effective treatment for mild-to-moderate secondary hyperparathyroidism in patients undergoing haemodialysis

Abstract

Background: Microwave ablation (MWA) is an effective treatment for severe secondary hyperparathyroidism (SHPT), but it can also be used for mild-to-moderate secondary hyperparathyroidism (SHPT). In this randomised, controlled study, the efficacy of MWA in the treatment of mild-to-moderate hyperparathyroidism is investigated.

Materials and methods: We assessed outcomes 12?months after the randomisation of 28 patients with mild-to-moderate SHPT. The subjects received either MWA plus calcitriol or calcitriol alone. The primary end-points were the rate of achieving target levels of intact parathyroid hormone (iPTH), changes in iPTH levels and the rate of patients developing severe SHPT.

Results: Primary end points: the overall rates of achieving target levels of iPTH were comparable between the MWA and calcitriol alone groups (24% vs. 22%, p?=?0.85). However, the rate of iPTH <150?pg/mL (lower limit of the target range) in the MWA group was higher than that in the calcitriol alone group (23% vs. 8%, p?=?0.02). The mean iPTH level in the MWA group after MWA was lower than that in the calcitriol alone group (373.09?±?322.31 vs. 552.28?±?361.87?pg/mL, p?<?0.001). There was a significant difference in the change in iPTH levels over time within the MWA group (p?<?0.001) but not in the calcitriol alone group. Only one patient developed severe SHPT in the MWA group, while six patients in the calcitriol alone group developed severe SHPT (p?=?0.04).

Conclusions: Compared with calcitriol alone, MWA plus calcitriol decreases iPTH levels and prevents the progression of mild-to-moderate SHPT.     

The efficacy and safety of microwave ablation in patients with retroperitoneal metastases

Background: Retroperitoneal metastases are common, and most present with symptoms; however, treatments for this condition are limited. This retrospective study verified the efficacy and safety of microwave ablation (MWA) in retroperitoneal metastases patients.

Methods: Patients with pathologically confirmed malignant carcinoma and imaging showing retroperitoneal metastases were enrolled and underwent MWA. The end-points included objective response rate, time to local progression (TTLP), overall survival, visual analogue scale (VAS) score, dose of morphine pre- and post-ablation and complications.

Results: Twenty-three patients were enrolled. The mean tumour diameter was 3.6?cm. Altogether, 29 tumour sites in 23 patients were ablated during 23 procedures; technical success was achieved in all 23 patients. The objective response and disease control rates were 95.7% and 100.0%, respectively. The mean TTLP and median OS were 22.8?months (95% CI: 16.1–29.6?months) and 10.6?months (95% CI: 7.4–13.8?months), respectively. In 13 patients with symptoms, the VAS values before ablation and 48?h, 1?month, 2?months, 3?months and 6?months after ablation were 5.38, 2.77 (p?=?0.015), 2.15 (p?=?0.001), 2.17 (p?=?0.001), 1.40 (p?=?0.000) and 1.71 (p?=?0.006), respectively. The corresponding morphine doses were 76.9?mg, 70.7?mg (p?=?0.584), 50.7?mg (p?=?0.031), 55.0?mg (p?=?0.097), 46.0?mg (p?=?0.057) and 40.0?mg (p?=?0.363), respectively. No ablation-associated mortality was observed. Major complications, minor complications and adverse events were observed in eight (34.8%), five (21.7%) and four (17.4%) patients, respectively.

Conclusion: MWA for the treatment of retroperitoneal metastases was effective and the complications were common.     

Safety and efficiency of microwave ablation for recurrent and persistent secondary hyperparathyroidism after parathyroidectomy: A retrospective pilot study

Background: Recurrent and persistent secondary hyperparathyroidism (SHPT) nodules have an incidence of 10–70% after surgery. The treatment of recurrent and persistent SHPT nodules is a challenge, and surgical resection of difficult-to-reach or post-operative adhesions often fails. Purpose: The aim of this research was to study the safety and effectiveness of microwave ablation (MWA) for recurrent and persistent SHPT. Materials and methods: This was a retrospective study of 11 patients enrolled with a total of 16 nodules, and MWA was employed to manage SHPT. The laboratory test results, including the intact parathyroid hormone (iPTH), serum calcium, phosphorus and alkaline phosphatase (ALP) levels, improvement of SHPT-related symptoms after ablation, and complications during and after MWA were recorded and analysed. Results: After ablation the value of iPTH was markedly decreased from 1570?±?1765?pg/mL to 287?±?239?pg/mL 1 day after MWA (p?<?0.05). The levels of serum calcium and phosphorus decreased from 2.51?±?0.23?mmol/L to 2.06?±?0.27?mmol/L (p?<?0.001) and 1.80?±?0.43?mmol/L to 1.48?±?0.32?mmol/L (p?<?0.05), respectively, 1 day after MWA. There was no significant difference in the ALP value before and after MWA (p?>?0.05). The clinical symptoms, including ostalgia, pruritus, disability, and restless legs, improved after MWA. Minor complications and side effects encountered during or after MWA include haematoma (1/11, 9%), transient hoarseness (2/11, 18.2%), hypocalcemia (6/11, 54.5%). No major complication occurred. Conclusion: MWA may be safe and effective to manage recurrent and persistent SHPT nodules; a definite conclusion needs to expand the sample size with a longer follow-up time.     

Real-time qualitative MR monitoring of microwave ablation in ex vivo livers

Purpose: Computed tomography (CT) and ultrasound-guided microwave ablations (MWA) are part of the established treatment of liver tumours. In spite of its potential advantages, magnetic resonance (MR) monitoring of MWA did not enter clinical practice because of the lack of compatible devices. The purpose of the current study was to prove the feasibility of real-time qualitative MR monitoring using a new MR-compatible MWA device.

Material and methods: We performed 27 MWA experiments with different durations (5, 10 and 15?min) on an ex vivo bovine liver model using a MR-compatible MWA device. We compared the diameters of the ablation zone as depicted on three T1-based sequences to those of the macroscopic specimen. The volume and the sphericity index of the macroscopic ablation area were calculated in order to characterise the device. Ablation pattern and artefacts on the three sequences were also taken into account.

Results: We obtained high-quality real-time images using all three sequences. The diameters as depicted on the MR sequences slightly overestimated the macroscopic ablation area but correlated significantly in all cases (p?r?=?0.96) and long-axis diameter (r?=?0.87), whereas starVIBE (r?=?0.85; r?=?0.72) and FLASH (r?=?0.75; r?=?0.84) correlated slightly less. Significantly more severe noise artefacts were observed on starVIBE compared to FLASH and VIBE sequences (p?Conclusion: The current ex vivo liver model experiment suggests that real-time qualitative MR monitoring of MWA is feasible. Further research using in vivo and human models are recommended.     

Microwave ablation of hyperplastic parathyroid glands is a treatment option for end-stage renal disease patients ineligible for surgical resection

Background: Secondary hyperparathyroidism (SHPT) is a frequently encountered problem in patients with end-stage renal disease (ESRD). Some patients with severe SHPT could not be managed by medical treatment and are ineligible for surgical resection.

Purpose: Our objective was to evaluate the efficacy, safety of microwave ablation (MWA) on these patients.

Materials and Methods: Between 1 April 2015 and 28 February 2017, 35 patients (M/F 19/16, age 49.8?±?12.9?years) were enrolled. All patients were treated with MWA. Levels of intact parathyroid hormone (iPTH) and of serum calcium and phosphorus were compared pre- and post-ablation. Repeated-measures ANOVA was used to compare treatment outcomes pre- and post-ablation.

Results: Complete ablation was achieved in all 63 glands in the 35 patients with SHPT. The mean follow-up time was 15.9?±?2.2?months. The maximum gland diameter was 6–31?mm (mean, 14.9?±?5.5?mm). The trends of the changes in iPTH and calcium levels showed a curve: the level of iPTH and calcium at 6?months post-ablation were lower than those pre-ablation (both p?<?.0001); after then iPTH remained relatively stable and the end of follow up, with no rebound (p?<?.0001), while instead of calcium at the end of follow up was not significantly lower than pre-ablation (p?=?.462). The trend in the change in phosphate levels showed a straight line; the level of phosphate at 6?months post-ablation and at the end of follow up both were significantly lower than pre-MWA (p?<?.001). There was no major complication.

Conclusions: In this series, MWA was used successfully to treat SHPT patients who are ineligible for surgical resection.     

Ultrasound-guided percutaneous microwave ablation vs. surgical resection for thoracoabdominal wall implants from hepatocellular carcinoma: intermediate-term results

Objective: The aims of this study were to compare the clinical outcomes between ultrasound (US)-guided percutaneous microwave ablation (MWA) and surgical resection (SR) in patients with thoracoabdominal wall implants from hepatocellular carcinom (HCC) and to identify the prognostic factors associated with the two treatment methods.

Materials and methods: A total of 47 patients (mean age, 56.7?±?15.9 years, range, 18–78 years; 34 men and 13 women) with 61 thoracoabdominal wall HCC seeding were included from April 2007 to May 2017. Twenty-five patients underwent US-guided MWA and 22 patients underwent SR. Survival, recurrence and liver function were compared between the two groups. Effect of changes in key parameters (i.e. overall survival (OS), disease-free survival (DFS) and local tumour reoccurrence-free (LTRF)) was statistically analysed with the log-rank test. Univariate and multivariate analyses were performed on several clinicopathological variables to identify factors affecting long-term outcome and recurrence.

Results: The OS, DFS and LTRF after MWA were comparable to those of SR (p?=0.493, p?=?0.578 and p?=0.270, respectively). Estimated 5-year overall survival rates were 63% after MWA and 48.1% after SR; for disease-free survival, estimated 5-year rates were 67.5% after MWA and 48.8% after SR; estimated 24-month LTRF rates were 71.3% after MWA and 87.8% after SR. The MWA group had less surgical time (p?=?<0.001), estimated blood loss (p =?<0.001) and post-operative hospitalisation (p?=?0.032) and cost (p?=?0.015). Multivariate analysis showed remnant intrahepatic tumour (p?=0.007), Child Pugh grade (p?=?0.009) and metastasis (p=?<0.001), were predictors for survival rate.

Conclusions: Ultrasound-guided percutaneous MWA is a safe and effective treatment method for metastatic HCC on the thoracoabdominal wall with similar outcomes to SR. Residual intrahepatic HCC, Child Pugh grade and distant metastasis are predictors for survival.     

Percutaneous microwave ablation of 5-6 cm unresectable hepatocellular carcinoma: local efficacy and long-term outcomes

Objective: This study aims to evaluate the local efficacy and long-term outcomes of microwave ablation (MWA) for treating large unresectable hepatocellular carcinomas (HCCs).

Methods: A total of 82 patients with 5-6?cm unresectable HCCs, who underwent a single MWA procedure during the period of January 2007 to July 2011, were retrospectively enrolled into this study. Percentages of technical success and complications of MWA and HCC local recurrence (LR) after MWA were determined. In addition, prognostic factors were screened and overall survival (OS) and recurrence-free survival (RFS) rates were estimated.

Results: One-, three- and five-year OS rates in this MWA-treated cohort were 92.7, 63.4 and 41.1%, respectively; and the corresponding RFS rates were 65.9, 31.7 and 23.0%, respectively. Primary technical efficacy was 89.0% after the first round of ablation, three (3.7%) patients developed major complications, and LR rate was 20.7%. Child-Pugh classification (p?p?=?.049) and LR (p?=?.002) were independent factors associated with OS, as determined by multivariate analysis.

Conclusions: MWA is safe and effective for the treatment of selected large HCCs, and provides an alternative treatment option for patients with unresectable HCCs. Furthermore, the favourable local efficacy of MWA could potentially improve long-term survival.     

Hepatocellular carcinoma abutting large vessels: comparison of four percutaneous ablation systems

Purpose: To compare overall local tumour progression (OLTP), defined as the failure of primary ablation or local tumour progression, with single applicator monopolar radiofrequency ablation (RFA), microwave ablation (MWA), cluster-RFA and multi-bipolar radiofrequency (mbpRFA) in the treatment of hepatocellular carcinoma (HCC)?≤?5?cm abutting large vessels (≥3?mm).

Materials and methods: This multicenter, retrospective, per-nodule study was performed from 2007 to 2015. The study was approved by the ethics review board, and informed consent was waived. A total of 160/914 HCC nodules treated by thermal ablation and abutting large vessels (40 per treatment group) treated by monopolar RFA, MWA, cluster-RFA or mbpRFA were matched for tumour size, alpha-feto-protein level and vessel size. OLTP rates were compared by the log-rank test and the multivariate Cox model after matching.

Results: No differences were observed in tumour size, vessel size or alpha-feto-protein levels among the three groups (p?=?1). The cumulative 4-year OLTP rates following monopolar RFA, cluster-RFA, multi-bipolar RFA and MWA were 50.5%, 16.3%, 16.3% and 44.2%, respectively (p?=?0.036). On multivariate Cox regression, vessel size ≥10?mm, monopolar RFA and MWA were independent risk factors of OLTP compared to cluster-RFA or mbpRFA.

Conclusion: Multi-applicator RFA provides better local tumour control in HCC abutting large vessels than single-applicator techniques (monopolar RFA or MWA).     

Combined microwave ablation and systemic chemotherapy for liver metastases from oesophageal cancer: Preliminary results and literature review

Purpose: Oesophageal cancer is a highly aggressive disease with about 50% of patients presenting with advanced or metastatic disease at initial diagnosis. In this study we assessed combined microwave ablation (MWA) and systemic chemotherapy in the treatment of liver metastases arising from oesophageal squamous cell carcinoma (OSCC). Materials and methods: Between February 2009 and June 2014, OSCC patients who underwent percutaneous MWA?+?concurrent systemic chemotherapy and systemic chemotherapy alone for liver metastases were enrolled in this study. Overall survival (OS) and progression-free survival (PFS) were recorded and compared between groups. Results: In total 15 patients with 25 liver metastases who underwent ultrasound-guided percutaneous MWA and chemotherapy were enrolled in this study. Technical success was achieved in 96% (24/25) of metastatic liver tumours. No major or minor complications associated with MWA procedures were observed. The median OS and PFS from initial MWA were 13 months and 4 months. The 1-, 2-, 3-, 4-year OS rates after MWA were 53.3%, 26.7%, 13.3%, and 13.3%, respectively. The 1- and 2-year PFS rates after MWA were 26.7% and 13.3%. The OS and PFS of the MWA?+?systemic chemotherapy group were superior than those of patients who received systemic chemotherapy alone (P?=?0.011 and 0.030, respectively). Conclusions: Combined MWA with systemic chemotherapy is a feasible, safe and effective treatment for liver metastases from OSCC.     

US-guided microwave ablation for secondary hyperparathyroidism in patients after renal transplantation: a pilot study

Objective: To assess the safety and efficacy of ultrasound-guided microwave ablation (MWA) in the treatment of patients who develop secondary hyperparathyroidism (SHPT) after renal transplantation (RT).

Methods: In total, nine patients, each with symptomatic SHPT caused by RT and at least one enlarged parathyroid gland, underwent MWA via hydrodissection. Intact parathyroid hormone (i-PTH), serum calcium, serum phosphorus, creatinine and blood urea nitrogen concentrations, before and after MWA, were assessed and compared.

Results: Complete ablation was achieved in all patients for a total of 14 ablated parathyroid glands. The mean follow-up time was 17.2?±?1.7?months post-operation. The mean maximum diameter of the parathyroid glands was 1.3?±?0.4?cm (range: 0.4–2.0?cm). The ablation power implemented was 30?W and the mean time for each parathyroid gland to achieve complete ablation was 287.5?±?83.4?s. The mean i-PTH, serum calcium and phosphorus concentrations at one day post-MWA (69.6?pg/mL, 2.23?±?0.29?mmol/L, 1.2 2?±?0.48?mmol/L, respectively) were significantly lower than those before MWA (780.0?pg/mL, 2.62?±?0.32?mmol/L, 1.39?±?0.61?mmol/L, respectively; p?<?.01), whereas the creatinine and blood urea nitrogen concentrations before and after MWA did not differ significantly from each other (p?>?.05). No significant differences were found between the biomarker concentrations observed at one day post-MWA and at the follow-ups (p?>?.05). No major operation-related complications occurred.

Conclusion: Ultrasound-guided MWA is a safe and effective technique for destroying parathyroid gland tissue in patients who develop SHPT after RT and its clinical effects are long-lasting.     

Clinical and survival outcomes of percutaneous microwave ablation for intrahepatic cholangiocarcinoma

Objective: To evaluate the outcomes of percutaneous microwave ablation (MWA) and explore the prognostic factors for the survival of patients with intrahepatic cholangiocarcinoma (ICC).

Methods: A total of 107 patients (age: mean 58.0?years, range 15–85?years) with 171 ICCs (maximum size ≤5?cm, tumour number per patient ≤3) who underwent MWA for ICC during January 2009 to February 2016 were selected, and their clinical and pathological data were collected and reviewed. The MWA-associated mortality, major complication rate and survival were evaluated. The prognostic factors for survival in patients with ICC were analysed with univariate and multivariate analyses.

Results: The median follow-up after MWA was 20.1?months (2.8–63.5?months). There was no procedure-associated death. The overall procedure-associated major complication rate was 2.8%. The median PFS after MWA was 8.9?months; PFS rates after 6, 12, 18 and 24?months were 67.4%, 41.5%, 18.2% and 8.7%. The median OS was 28.0?months; OS rates after 1, 3 and 5?years were 93.5%, 39.6% and 7.9%. Child-Pugh class A and less tumour number were identified as factors predictive of prolonged PFS (HR for Child–Pugh class: 2.62, p?=?0.001; HR for tumour number: 2.07, p?=?0.002) and OS (HR for Child–Pugh class: 4.14, p?p?=?0.024).

Conclusions: Percutaneous ultrasound-guided MWA is safe and effective for ICC. Child–Pugh class A and less tumour number predict prolonged PFS and OS in patients with ICC treated by MWA.     

Comparison between microwave ablation and lobectomy for stage I non-small cell lung cancer: a propensity score analysis

Purpose: To compare the effectiveness and complication between microwave ablation and lobectomy for stage I non-small cell lung cancer.

Materials and Methods: This retrospective study was approved by two institutional ethics committees and all patients were provided with informed consent. From January 2000 to December 2010, 54 and 795 stage I patients who underwent microwave ablation and lobectomy were included in this study. A matched cohort composed of 54 and 108 patients in the microwave ablation and the lobectomy group were selected after adjustment with 1:2 propensity score matching. The overall survival and disease-free survival were evaluated. Survival curves were constructed with the Kaplan–Meier method and compared by using the log-rank test.

Results: The 1, 3 and 5-year Overall survive were 100, 92.6 and 50.0% for MWA group and 100, 90.7 and 46.3% for lobectomy group. The 1, 3 and 5-year disease free survival was 98.1, 79.6 and 37.0% for MWA group and 98.1, 81.5 and 29.6% for lobectomy group. There was no significant difference between two groups in overall survival (p?=?0.608) and disease free survival (p?=?0.672). Additionally, local or distant metastasis rate (p?=?0.544) were not significantly different between two groups while the complication rate in the MWA group was significantly lower than the lobectomy group (p?=?0.008).

Conclusion: Microwave ablation has similar therapeutic effect compared with lobectomy for stage I non-small cell lung cancer, but with fewer complication and less pain.     

Percutaneous microwave ablation (MWA) increased the serum levels of VEGF and MMP-9 in Stage I non-small cell lung cancer (NSCLC)

Background: Lung cancer is the leading cause of cancer death around the world. Percutaneous microwave ablation (MWA) is an emerging treatment strategy for medically inoperable early-stage non-small cell lung cancer (NSCLC). In this study, we investigated the association of MWA and serum angiogensis promoters VEGF and MMP-9 in these patients subgroup.

Methods: We enrolled 52 patients with Stage I NSCLC patients in this study. For each patient, blood samples were drawn by venous puncture, one immediately prior to MWA and the others on Post-Procedure Days (PPD) 1, 3, 5, 7, 10 and 14. Serum samples were analysed for VEGF and MMP-9 levels with use of commercially available enzyme-linked immunosorbent assay. Also, blood samples of 28 healthy volunteers were set as the healthy controls.

Results: We did not observe a significant difference of serum VEGF and MMP-9 between NSCLC patients and healthy controls. The VEGF levels increased on the first day (256.0?±?6.16?pg/ml, p?p?p?p?p?p?>?0.05). The highest MMP-9 level was observed on PPD5 (399.7?±?17.70?ng/ml, p?Conclusion: Our preliminary results indicated that percutaneous MWA resulted in increased serum levels of VEGF and MMP-9 in Stage I NSCLC patients. Antiangiogenesis approaches may be helpful for patients defending against metastases during the immediate post-ablation time window.     

Microwave ablation is effective against liver metastases from gastric adenocarcinoma

Purpose: The resection rate for liver metastases from gastric cancer is only 1.4–21.1%. This study aimed to evaluate the safety and therapeutic efficacy of microwave ablation (MWA) for liver metastases from gastric adenocarcinoma (LMGC).

Materials and methods: A database of 108 gastric adenocarcinoma patients with liver metastases who underwent MWA (n?=?32) or systemic chemotherapy (n?=?76) for LMGC between 2008 and 2016 was reviewed. Overall survival curves were assessed and compared based on different therapies.

Results: All the patients were followed up for a median of 15?months (range, 2–68?months). The median cumulative survival times of patients after MWA and systemic chemotherapy were 25 (95% confidence interval (CI) 16.5–33.5) months and 12 (95% CI 7.7–16.3) months, respectively (HR 1.751, 95% CI 1.077–2.845; p?=?.015). The 1-, 3-, and 5- year survival rates were 80.9%, 31.2%, and 16.7% (MWA group); and 50.0%, 18.8%, and 5.4% (chemotherapy group), respectively. In the MWA group, side effects were reported in eight patients who developed abdominal pain, transient fever, or nausea. Dominant size, number of liver metastases, therapeutic modalities, and presence of extrahepatic metastases showed significant prognostic value in univariate analyses; while the latter three were identified as independent prognostic factors in multivariate regression analysis.

Conclusions: MWA is a safe and useful alternative for liver metastases from gastric adenocarcinoma in selected patients.     

Technical analysis of US imaging for precise microwave ablation for benign breast tumours

Purpose: To determine the characteristics of ultrasound (US) imaging of completely ablated cases and the effects of duration and clinical experience on accurate microwave ablation (MWA) for the treatment of benign breast tumours.

Methods: With written informed consent and approval of the institutional ethics committee, patients with symptomatic or palpable benign breast tumours (longest diameter, 7–32?mm), to whom MWA (2450?MHz) was performed, were enrolled in this prospective nonrandomised study. US and contrast-enhanced US (CEUS) images were applied for follow-up and analysed.

Results: Forty-seven consecutive patients with 52 completely ablated tumours were enrolled. Of these 52 tumour ablations in US, 16 ablations were defined as concentric type, and 36 were defined as nonconcentric type. Of these 52 ablations, 7 cases were defined as nonaccurate ablation with the largest margin ≥10?mm in US. The nonaccurate ablation rate in the training group (the first consecutive 30 cases, 7/30) was significant higher than that (the last 22 cases, 0/22) in the practiced group (p?=?0.016). Of 38 completely ablated cases (9?mm?70?s group was significant larger than that in <70?s group (p?=?0.019).

Conclusions: Experience was important for accurate MWA in the treatment of benign breast tumour, and at least 30 cases training was recommended. Nevertheless, clinical trials are still required to validate our findings in the future.     

Safety and advantages of combined resection and microwave ablation in patients with bilobar hepatic malignancies

Abstract

Background: The multimodality approach has significantly improved outcomes for hepatic malignancies. Microwave ablation is often used in isolation or succession, and seldom in combination with resection. Potential benefits and pitfalls from combined resection and ablation therapy in patients with complex and extensive bilobar hepatic disease have not been well defined.

Methods: A review of the University of Louisville prospective Hepato-Pancreatico-Biliary Patients database was performed with multi-focal bilobar disease that underwent microwave ablation with resection or microwave only included.

Results: One hundred and eight were treated with microwave only (MWA, n?=?108) or combined resection and ablation (CRA, n?=?84) and were compared with similar disease-burden patients undergoing resection only (n?=?84). The groups were comparable except that the MWA group was older (p?=?.02) and with higher co-morbidities (diabetes, hepatitis). The resection group had larger tumours (4 vs. 3.2 and 3?cm) but the CRA group had more numerous lesions (4 vs. 3 and 2, p?=?.002). Short-term outcomes including morbidity (47.6% vs. 43%, p?=?.0715) were similar between the CRA and resection only groups. Longer operative time (164 vs. 126?min, p?=?.003) and need for blood transfusion (p?=?.001) were independent predictors of complications. Survival analyses for colorectal metastasis patients (n?=?158) demonstrated better overall survival (OS) (43.9 vs. 37.6 and 30.5 months, p?=?.035), disease-free survival (DFS) (38 vs. 26.6 and 16.9 months, p?=?.028) and local recurrence-free survival (LRFS) (55.4 vs. 17 and 22.9 months, p?<?.001) with resection only.

Conclusion: The use of microwave ablation in addition to surgical resection did not significantly increase the morbidities or short-term outcomes. In combination with systemic and other local forms of therapy, combined resection and ablation is a safe and effective procedure.     

Evaluation of microwave ablation of liver malignancy with enabled constant spatial energy control to achieve a predictable spherical ablation zone

Objectives: To evaluate the clinical performance of a new microwave ablation (MWA) system with enabled constant spatial energy control (ECSEC) to achieve spherical ablation zones in the treatment of liver malignancies.

Materials and methods: In this retrospective study, 56 hepatic tumours in 48 patients (23 men, 25 women; mean age: 59.6 years) were treated using a new high-frequency MWA-system with ECSEC. Parameters evaluated were technical success, technical efficacy, tumour diameter, tumour and ablation volume, complication rate, 90-day mortality, local tumour progression (LTP) at the 12-month follow-up, ablative margin and ablation zone sphericity. These parameters were compared using the Kruskal–Wallis test with the same parameters collected retrospectively from cohorts of patients treated with conventional high-frequency (HF) MWA (n?=?20) or low-frequency (LF) MWA (n?=?20).

Results: Technical success was achieved in all interventions. The technical efficacy was 100% (ECSEC) vs. 100% (LF-MWA) vs. 95% (HF-MWA). There were no intra-procedural deaths or major complications. Minor complications occurred in 3.57% (2/56), 0% (0/20) and 0% (0/20) of the patients, respectively. The one-year mortality rate was 16.1% (9/56), 15% (3/20) and 10% (2/20), respectively. The LTP was 3.57% (2/56), 5% (1/20) and 5% (1/20), respectively. The median deviation from ideal sphericity (1.0) was 0.135 (ECSEC) vs. 0.344 (LF-MWA) vs. 0.314 (HF-MWA) (p?p?Conclusions: Microwave ablation of liver malignancies is a safe and efficient treatment independent of the system used. Hepatic MWA with ECSEC achieves significantly more spherical ablation zones and higher minimal ablative margins.     

Computed tomography-guided percutaneous microwave ablation of hepatocellular carcinoma in challenging locations: safety and efficacy of high-power microwave platforms

Objective: To evaluate the clinical efficacy/safety of CT-guided percutaneous microwave ablation for HCC in challenging locations using high-power microwave platforms.

Materials and methods: A retrospective review was conducted in 26 patients with 36 HCC tumours in challenging locations (hepatic dome, subcapsular, close to the heart/diaphragm/hepatic hilum, exophytic) undergoing CT-guided percutaneous microwave ablation in a single centre since January 2011. Two different microwave platforms were used both operating at 2.45?GHz: AMICA and Acculis MWA System. Patient demographics including age, sex, tumour size and location, as well as technical details were recorded. Technical success, treatment response, patients survival and complication rate were evaluated.

Results: Treated tumours were located in the hepatic dome (n?=?14), subcapsularly (n?=?16), in proximity to the heart (n?=?2) or liver hilum (n?=?2), while two were exophytic tumours at segment VI (n?=?2). Mean tumour diameter was 3.30?cm (range 1.4–5?cm). In 3/26 patients (diameter?>4?cm), an additional session of DEB-TACE was performed due to tumour size. Technical success rate was 100%; complete response rate was recorded in 33/36 tumours (91.6%). According to Kaplan–Meier analysis, survival rate was 92.3% and 72.11% at 24- and 60-month follow-up, respectively. There were no major complications; two cases of minor pneumothorax and two cases of small subcapsular haematoma were resolved only with observation requiring no further treatment.

Conclusion: CT-guided percutaneous microwave ablation for hepatocellular carcinoma tumours in challenging locations and up to 5?cm in diameter can be performed with high efficacy and safety rates.     

Ablation therapy of non-colorectal cancer lung metastases: retrospective analysis of tumour response post-laser-induced interstitial thermotherapy (LITT), radiofrequency ablation (RFA) and microwave ablation (MWA)

Purpose: To retrospectively compare the local tumour response and survival rates in patients with non-colorectal cancer lung metastases post-ablation therapy using laser-induced thermotherapy (LITT), radiofrequency ablation (RFA) and microwave ablation (MWA).

Material and methods: Retrospective analysis of 175 computed tomography (CT)-guided ablation sessions performed on 109 patients (43 males and 66 females, mean age: 56.6 years). Seventeen patients with 22 lesions underwent LITT treatment (tumour size: 1.2–4.8?cm), 29 patients with 49 lesions underwent RFA (tumour size: 0.8–4.5?cm) and 63 patients with 104 lesions underwent MWA treatment (tumour size: 0.6–5?cm). CT scans were performed 24-h post-therapy and on follow-up at 3, 6, 12, 18 and 24 months.

Results: The overall-survival rates at 1-, 2-, 3- and 4-year were 93.8, 56.3, 50.0 and 31.3% for patients treated with LITT; 81.5, 50.0, 45.5 and 24.2% for patients treated with RFA and 97.6, 79.9, 62.3 and 45.4% for patients treated with MWA, respectively. The mean survival time was 34.14 months for MWA, 34.79 months for RFA and 35.32 months for LITT. In paired comparison, a significant difference could be detected between MWA versus RFA (p?=?0.032). The progression-free survival showed a median of 23.49?±?0.62 months for MWA,19.88?±?2.17 months for LITT and 16.66?±?0.66 months for RFA (p?=?0.048). The lowest recurrence rate was detected in lesions ablated with MWA (7.7%; 8 of 104 lesions) followed by RFA (20.4%; 10 of 49 lesions) and LITT (27.3%; 6 of 22 lesions) p value of 0.012. Pneumothorax was detected in 22.16% of MWA ablations, 22.73% of LITT ablations and 14.23% of RFA ablations.

Conclusion: LITT, RFA and MWA may provide an effective therapeutic option for non-colorectal cancer lung metastases with an advantage for MWA regarding local tumour control and progression-free survival rate.     

Analysis of minimally invasive directional antennas for microwave tissue ablation

Abstract

Purpose: Microwave ablation (MWA) applicators capable of creating directional heating patterns offer the potential of simplifying treatment of targets in proximity to critical structures and avoiding the need for piercing the tumour volume. This work reports on improved directional MWA antennas with the objectives of minimising device diameter for percutaneous use (≤ ～13 gauge) and yielding larger ablation zones.

Methods: Two directional MWA antenna designs, with a modified monopole radiating element and spherical and parabolic reflectors are proposed. A 3D-coupled electromagnetic heat transfer with temperature-dependent material properties was implemented to characterise MWA at 40 and 77 W, for 5 and 10?min. Simulations were also used to assess antenna impedance matching within liver, kidney, lung, bone and brain tissue. The two antenna designs were fabricated and experimentally evaluated with ablations in ex vivo tissue at the two power levels and treatment durations (n?=?5 repetitions for each group).

Results: The computed specific absorption rate (SAR) patterns for both antennas were similar, although simulations indicated slightly greater forward penetration for the parabolic antenna. Based on simulations for antennas inserted within different tissues, the proposed antenna design appears to offer good impedance matching for a variety of tissue types. Experiments in ex vivo tissue showed radial ablation depths of 19?±?0.9?mm in the forward direction for the applicator with spherical reflector and 18.7?±?0.7?mm for the applicator with parabolic reflector.

Conclusion: These results suggest the applicator may be suitable for creating localised directional ablation zones for treating small and medium-sized targets with a percutaneous approach.