Shaping the future of microwave tumor ablation: a new direction in precision and control of device performance.

Microwave ablation (MWA) is becoming an increasingly important minimally invasive treatment option for localized tumors in many organ systems due to recent advancements in microwave technology that have conferred many advantages over other tumor ablation modalities. Despite these improvements in technology and development of applicators for site-specific tumor applications, the vast majority of commercially available MWA applicators are generally designed to create large-volume, symmetric, ellipsoid or spherically-shaped treatment zones and often lack the consistency, predictability, and spatial control needed to treat tumor targets near critical structures that are vulnerable to inadvertent thermal injury. The relatively new development and ongoing translation of directional microwave ablation (DMWA) technology, however, has the potential to confer an added level of control over the treatment zone shape relative to applicator position, and shows great promise to expand MWA's clinical applicability in treating tumors in challenging locations. This paper presents a review of the industry-standard commercially available MWA technology, its clinical applications, and its limitations when used for minimally-invasive tumor treatment in medical practice followed by discussion of new advancements in experimental directional microwave ablation (DMWA) technology, various techniques and approaches to its use, and examples of how this technology may be used to treat tumors in challenging locations that may otherwise preclude safe treatment by conventional omni-directional MWA devices.

Cryoablation for Palliation of Painful Bone Metastases: The MOTION Multicenter Study.

Purpose: To assess the clinical effectiveness of cryoablation for palliation of painful bone metastases. Materials and Methods: MOTION (Multicenter Study of Cryoablation for Palliation of Painful Bone Metastases) (ClinicalTrials.gov NCT02511678) was a multicenter, prospective, single-arm study of adults with metastatic bone disease who were not candidates for or had not benefited from standard therapy, that took place from February 2016 to March 2018. At baseline, participants rated their pain using the Brief Pain Inventory-Short Form (reference range from 0 to 10 points); those with moderate to severe pain, who had at least one metastatic candidate tumor for ablation, were included. The primary effectiveness endpoint was change in pain score from baseline to week 8. Participants were followed for 24 weeks after treatment. Statistical analyses included descriptive statistics and logistic regression to evaluate changes in pain score over the postprocedure follow-up period. Results: A total of 66 participants (mean age, 60.8 years ± 14.3 [standard deviation]; 35 [53.0%] men) were enrolled and received cryoablation; 65 completed follow-up. Mean change in pain score from baseline to week 8 was -2.61 points (95% CI: -3.45, -1.78). Mean pain scores improved by 2 points at week 1 and reached clinically meaningful levels (more than a 2-point decrease) after week 8; scores continued to improve throughout follow-up. Quality of life improved, opioid doses were stabilized, and functional status was maintained over 6 months. Serious adverse events occurred in three participants. Conclusion: Cryoablation of metastatic bone tumors provided rapid and durable pain palliation, improved quality of life, and offered an alternative to opioids for pain control.Keywords: Ablation Techniques, Metastases, Pain Management, Radiation Therapy/OncologySupplemental material is available for this article.© RSNA, 2021.

Microwave Ablation in the Liver: An Update.

Hepatocellular carcinoma (HCC) and secondary hepatic malignancies, most often arising from colorectal cancer, are a leading cause of morbidity and cancer-related deaths worldwide. In lieu of first-line surgical resection, which is precluded in more than 75% of cases due to underlying comorbid conditions or locally advanced disease, several minimally-invasive transarterial and thermal ablation procedures have emerged as safe and effective alternative therapies in select patients. Among the thermal ablative techniques, microwave ablation (MWA) has become the preferred treatment modality because of its operational convenience and superior heating profile, allowing for larger ablation zones and reduced treatment times while maintaining high technical success rates. To date, MWA has been demonstrated to provide equivalent, and in some cases improved, clinical outcomes compared to radiofrequency ablation (RFA) in patients with inoperable HCC or oligometastatic disease. Active areas of investigation include the comparison of MWA and transarterial therapies, such as transarterial chemoembolization (TACE), as well as combined multimodality therapies. Here we review the emerging topic of MWA for the treatment of hepatic malignancies by examining staging and treatment strategies, available technologies, procedural protocol and technique, and clinical outcomes.

Renal Cell Carcinoma: Comparison of RENAL Nephrometry and PADUA Scores with Maximum Tumor Diameter for Prediction of Local Recurrence after Thermal Ablation.

Purpose To evaluate the performance of the radius, exophytic or endophytic, nearness to collecting system or sinus, anterior or posterior, and location relative to polar lines (RENAL) nephrometry and preoperative aspects and dimensions used for anatomic classification (PADUA) scoring systems and other tumor biometrics for prediction of local tumor recurrence in patients with renal cell carcinoma after thermal ablation. Materials and Methods This HIPAA-compliant study was performed with a waiver of informed consent after institutional review board approval was obtained. A retrospective evaluation of 207 consecutive patients (131 men, 76 women; mean age, 71.9 years ± 10.9) with 217 biopsy-proven renal cell carcinoma tumors treated with thermal ablation was conducted. Serial postablation computed tomography (CT) or magnetic resonance (MR) imaging was used to evaluate for local tumor recurrence. For each tumor, RENAL nephrometry and PADUA scores were calculated by using imaging-derived tumor morphologic data. Several additional tumor biometrics and combinations thereof were also measured, including maximum tumor diameter. The Harrell C index and hazard regression techniques were used to quantify associations with local tumor recurrence. Results The RENAL (hazard ratio, 1.43; P = .003) and PADUA (hazard ratio, 1.80; P < .0001) scores were found to be significantly associated with recurrence when regression techniques were used but demonstrated only poor to fair discrimination according to Harrell C index results (C, 0.68 and 0.75, respectively). Maximum tumor diameter showed the highest discriminatory strength of any individual variable evaluated (C, 0.81) and was also significantly predictive when regression techniques were used (hazard ratio, 2.98; P < .0001). For every 1-cm increase in diameter, the estimated rate of recurrence risk increased by 198%. Conclusion Maximum tumor diameter demonstrates superior performance relative to existing tumor scoring systems and other evaluated biometrics for prediction of local tumor recurrence after renal cell carcinoma ablation. © RSNA, 2016.

Effectiveness and safety of computed tomography-guided radiofrequency ablation of renal cancer: a 14-year single institution experience in 203 patients.

OBJECTIVES: To define effectiveness and safety of CT-guided radiofrequency ablation (RFA) of renal tumours and prognostic indicators for treatment success. METHODS: Patients with a single treatment of a solitary, biopsy-proven renal tumour with intent to cure over a 14-year period were included (n = 203). Probability of residual disease over time, complication rates and all-cause mortality were assessed in relation to multiple variables. RESULTS: Mean tumour size was 2.5 cm (range 1.0-6.0). Mean follow-up was 34.1 months (range 1-131). There was an increase in likelihood of residual disease for tumours ≥3.5 cm (P < 0.05), clear cell subtype of renal cell carcinoma (P ≤ 0.005) and maximum treatment temperature ≤70 °C (P < 0.05). There was a decrease in likelihood of residual disease for exophytic tumours (P = 0.01) and no difference based on age, gender, tumour location or type of radio freqency (RF) electrode used. Major complications occurred in 3.9 %. Median post-treatment survival was 7 years for patients with tumours <4 cm, and 5-year overall survival was 80 %. Probability of minor complication increased with tumour size (P = 0.03), as did all-cause mortality (P = 0.005). CONCLUSIONS: CT-guided RFA is safe and effective for early-stage renal cancer, particularly for exophytic tumours measuring <3.5 cm. Overall 5-year survival with tumours <4 cm is comparable to partial nephrectomy. KEY POINTS: • Prognostic indicators for success of CT-guided RFA of renal tumours are reported. • Tumour size ≥3.5 cm confers an increased risk for residual tumour. • Clear cell renal cell carcinoma subtype confers increased risk for residual tumour. • Tmax <70 °C within the ablation zone confers increased risk for residual tumour. • Exophytic tumours have a lower probability of residual disease.

Microwave ablation of focal hepatic malignancies regardless of size: A 9-year retrospective study of 64 patients.

PURPOSE: To retrospectively evaluate the safety and efficacy of microwave ablation (MWA) as treatment for single, focal hepatic malignancies. MATERIALS AND METHODS: Institutional review board approval was obtained for this HIPAA-compliant study. From December 2003 to May 2012, 64 patients were treated with MWA for a single hepatic lesion, in 64 sessions. Hepatocellular carcinoma (HCC) was treated in 25 patients (geometric mean tumor size, 3.33-cm; 95% CI, 2.65-4.18-cm; range, 1.0-12.0-cm), metastatic colorectal cancer (CRC) was treated in 27 patients (geometric mean tumor size, 2.7-cm; 95% CI, 2.20-3.40-cm; range, 0.8-6.0-cm), and other histological-types were treated in 12 patients (geometric mean tumor size, 3.79-cm; 95% CI, 2.72-5.26-cm; range, 1.7-8.0-cm). Kaplan-Meier (K-M) method was used to analyze time event data. Chi-square and correlation evaluated the relationship between tumor size and treatment parameters. RESULTS: Technical success rate was 95.3% (61/64). Treatment parameters were tailored to tumor size; as size increased more antennae were used (p<0.001), treatment with multiple activations increased (p<0.028), and treatment time increased (p<0.001). There was no statistically significant relationship between time to recurrence and tumor size, number of activations, number of antennae, and treatment time. At one-year, K-M analysis predicted a likelihood of local recurrence of 39.8% in HCC patients, 45.7% in CRC metastases patients, and 70.8% in patients with other metastases. Median cancer specific survivals for patients were 38.3 months for HCC patients, 36.3 months for CRC metastases, and 13.9 months for other histological-types. Complications occurred in 23.4% (15/64) of sessions. CONCLUSION: In our sample, tumor size did not appear to impact complete ablation rates or local recurrence rates for focal hepatic malignancies treated with MWA.

Percutaneous ablation for small renal masses-imaging follow-up.

Image-guided percutaneous thermal ablation is a safe and effective nephron-sparing alternative to surgical resection for the treatment of small renal tumors. Assessment of treatment efficacy relies heavily on interval follow-up imaging after treatment. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) both play a pivotal role in evaluating the treatment zone, identifying residual tumor, and detecting early and delayed procedure-related complications. This article discusses a surveillance imaging protocol for patients who undergo percutaneous thermal ablation of renal tumors, and also illustrates the typical appearances of both successfully treated tumors and residual disease on contrast-enhanced CT or MRI. In addition, it discusses the imaging appearance of potential early and delayed treatment-related complications to facilitate their prompt detection and management.

How to set up a successful tumor ablation practice.

Tumor ablation services have increased in prevalence across the country and can now be found in modern health care systems of all sizes. These services have become an integral part of the coordinated multidisciplinary approach to patient care that must take place at any oncologic center of excellence. However, building a reputable tumor ablation practice at an institutional level can be a very difficult task as there are many financial, political, and material considerations that must be addressed during the early phases of operation to ensure its success. This article discusses each of these considerations in turn and provides insight into ways to overcome the inherent challenges faced when bringing all of the necessary elements together to create a thriving tumor ablation practice at an institutional level.

Interventional spine procedures for management of chronic low back pain-a primer.

Chronic low back pain is a common clinical condition. Percutaneous fluoroscopic-guided interventions are safe and effective procedures for the management of chronic low back pain, which can be performed in an outpatient setting. Interventional radiologists already possess the technical skills necessary to perform these interventions effectively so that they may be incorporated into a busy outpatient practice. This article provides a basic approach to the evaluation of patients with low back pain, as well as a review of techniques used to perform the most common interventions using fluoroscopic guidance.

Solid renal masses: effectiveness and safety of image-guided percutaneous radiofrequency ablation.

With increasing emphasis on minimally invasive nephron-sparing techniques for treatment of renal tumors, image-guided percutaneous radiofrequency ablation (RFA) has emerged as a safe and effective method of tumor eradication that may be performed on an outpatient basis, with relatively low morbidity and mortality. This review addresses the clinical and technical considerations, risks, complications, and currently reported efficacy data pertaining to RFA of renal tumors, as well as the standardized approach to treatment and follow-up currently used in our practice.

Radiofrequency ablation and percutaneous ethanol injection treatment for recurrent local and distant well-differentiated thyroid carcinoma.

OBJECTIVE: To assess the long-term efficacy of radiofrequency ablation (RFA) and percutaneous ethanol (EtOH) injection treatment of local recurrence or focal distant metastases of well-differentiated thyroid cancer (WTC). BACKGROUND: RFA and EtOH injection techniques are new minimally invasive surgical alternatives for treatment of recurrent WTC. We report our experience and long-term follow-up results using RFA or EtOH ablation in treating local recurrence and distant focal metastases from WTC. METHODS: Twenty patients underwent treatment of biopsy-proven recurrent WTC in the neck. Sixteen of these patients had lesions treated by ultrasound-guided RFA (mean size, 17.0 mm; range, 8-40 mm), while 6 had ultrasound-guided EtOH injection treatment (mean size, 11.4 mm; range, 6-15 mm). Four patients underwent RFA treatment of focal distant metastases from WTC. Three of these patients had CT-guided RFA of bone metastases (mean size, 40.0 mm; range, 30-60 mm), and 1 patient underwent RFA for a solitary lung metastasis (size, 27 mm). Patients were then followed with routine ultrasound, I whole body scan, and/or serum thyroglobulin levels for recurrence at the treatment site. RESULTS: No recurrent disease was detected at the treatment site in 14 of the 16 patients treated with RFA and in all 6 patients treated with EtOH injection at a mean follow-up of 40.7 and 18.7 months, respectively. Two of the 3 patients treated for bone metastases are free of disease at the treatment site at 44 and 53 months of follow-up, respectively. The patient who underwent RFA for a solitary lung metastasis is free of disease at the treatment site at 10 months of follow-up. No complications were experienced in the group treated by EtOH injection, while 1 minor skin burn and 1 permanent vocal cord paralysis occurred in the RFA treatment group. CONCLUSIONS: RFA and EtOH ablation show promise as alternatives to surgical treatment of recurrent WTC in patients with difficult reoperations. Further long-term follow-up studies are necessary to determine the precise role these therapies should play in the treatment of recurrent WTC.

Reassessment of parathyroid hormone monitoring during parathyroidectomy for primary hyperparathyroidism after 2 preoperative localization studies.

HYPOTHESIS: For patients with primary hyperparathyroidism and patients with 2 localization studies showing the same single location of parathyroid disease, use of intraoperative parathyroid hormone (IOPTH) measurement does not significantly increase the success of minimally invasive parathyroidectomy. DESIGN: Retrospective cohort study. SETTING: Experience of 2 academic centers over 5 years (at Brigham and Women's Hospital, Boston, Mass) and almost 4 years (at Rhode Island Hospital, Providence). PATIENTS: A total of 569 patients with primary hyperparathyroidism who underwent technetium Tc 99m sestamibi (MIBI) parathyroid imaging and neck ultrasonography (US). MAIN OUTCOME MEASURES: Incidence of correct prediction of location and extent of disease. RESULTS: In 322 patients (57%), MIBI and US imaging identified the same single site of disease. In 319 (99%) of these 322 patients, surgical exploration confirmed a parathyroid adenoma at that site, and the IOPTH levels normalized on removal. In 3 (1%) of the 322 patients, IOPTH measurement identified unsuspected additional disease. In 3 (1%) of the remaining 319 patients, IOPTH-guided removal of a single adenoma failed to correct hypercalcemia. Therefore, the failure rate of surgery in patients with positive MIBI and positive US imaging was 1% with IOPTH measurement and 2% without IOPTH measurement (P = .50). In 201 (35%) of the 569 patients, only 1 of the 2 studies recognized an abnormality or the studies disagreed on location. In these cases, either MIBI imaging or US imaging (if MIBI imaging was negative) failed to predict the correct site or extent of disease in 76 (38%) of the 201 patients (P<.001 vs concordant studies). CONCLUSIONS: In primary hyperparathyroidism, concordant preoperative localization with MIBI and US imaging is highly accurate. Use of IOPTH measurement in these cases adds only marginal benefit. When only 1 of the 2 studies identifies disease or the studies conflict, however, IOPTH measurement remains essential during minimally invasive parathyroidectomy.

Risk for malignancy of thyroid nodules as assessed by sonographic criteria: the need for biopsy.

OBJECTIVE: To correlate sonographic and color Doppler characteristics of thyroid nodules with the results of sonographically guided fine-needle aspiration biopsy to establish the relative importance of these features in predicting risk for malignancy. METHODS: We retrospectively analyzed the sonographic features of 34 malignant and 36 benign thyroid nodules with respect to size, echogenicity, echo structure, shape, border, calcification, and internal vascularity. Individual features and combinations of features were analyzed for their correlation with benign or malignant disease. A comparative analysis of several authors' previously proposed methods for distinguishing between benign and malignant nodules using sonographic criteria was also performed to determine their sensitivity and specificity in predicting nodule disease within our study data. RESULTS: Nodule size ranged from 0.8 to 4.6 cm in greatest dimension (mean, 1.96 cm; SD, 0.877 cm). The prevalence of malignancy in our study population was estimated to be nearly 5.33%. Intragroup comparison of sonographic features among benign and malignant nodules resulted in identification of intrinsic calcification as the only statistically significant predictor of malignancy (35.3% sensitive and 94.4% specific; P < .005). Presence of a "snowstorm" pattern of calcification was 100% specific for malignancy. Echogenicity, echo structure, shape, border classification, and grade of internal vascularity did not show any significant difference between benign and malignant nodules in this study. Various combinations of features previously suggested to be significant predictors of malignancy were also analyzed and shown to have very little sensitivity or specificity in predicting benign or malignant disease among nodules in our study population. CONCLUSIONS: This study indicates that the presence of intrinsic microcalcification is the only statistically reliable criterion on which to base increased suspicion for malignancy in thyroid nodules. Our results indicate the need for biopsy in determining further workup. All nodules that show the presence of intrinsic microcalcification should undergo biopsy, particularly if calcifications have a snowstorm appearance on sonography.