Percutaneous cryoablation of renal tumors: patient selection, technique, and postprocedural imaging

Stage IA papillary and chromophobe renal cell carcinoma: effectiveness of cryoablation and partial nephrectomy

OBJECTIVES

To evaluate the effectiveness of cryoablation compared to partial nephrectomy in patients with stage IA papillary and chromophobe renal cell carcinoma (pRCC; chRCC).

MATERIAL AND METHODS

The 2004-2016 National Cancer Database was queried for adult patients with stage IA pRCC or chRCC treated with cryoablation or partial nephrectomy. Patients receiving systemic therapy or radiotherapy, as well as those with bilateral RCC or prior malignant disease were excluded. Overall survival (OS) was assessed using Kaplan-Meier plots and Cox proportional hazard regression models. Nearest neighbor propensity matching (1:1 cryoablation:partial nephrectomy, stratified for pRCC and chRCC) was used to account for potential confounders.

RESULTS

A total of 11122 stage IA renal cell carcinoma patients were included (pRCC 8030; chRCC 3092). Cryoablation was performed in 607 (5.5%) patients, and partial nephrectomy in 10515 (94.5%) patients. A higher likelihood of cryoablation treatment was observed in older patients with non-private healthcare insurance, as well as in those with smaller diameter low-grade pRCC treated at non-academic centers in specific US geographic regions. After propensity score matching to account for confounders, there was no statistically significant difference in OS comparing cryoablation vs partial nephrectomy in patients with pRCC (HR = 1.3, 95% CI: 0.96-1.75, p = 0.09) and those with chRCC (HR = 1.38, 95% CI: 0.67-2.82, p = 0.38).

CONCLUSION

After accounting for confounders, cryoablation, and partial nephrectomy demonstrated comparable OS in patients with stage IA papillary and chromophobe RCC. Cryoablation is a reasonable treatment alternative to partial nephrectomy for these histological RCC subtypes when radiologically suspected or diagnosed after biopsy.

CRITICAL RELEVANCE STATEMENT

Cryoablation might be considered as an upfront treatment alternative to partial nephrectomy in patients with papillary and chromophobe stage IA renal cell carcinoma, as both treatment approaches yield comparable oncological outcomes.

KEY POINTS

The utilization of cryoablation for stage IA papillary and chromophobe RCC increases. In the National Cancer Database, we found specific patterns of use of cryoablation. Cryoablation and partial nephrectomy demonstrate comparable outcomes after accounting for confounders.

Cryoablation combined with a clinical Chinese medicine for the treatment of lung cancer

Cryoablation has been clinically applied to the treatment of lung cancer, but cryoablation has the problem of incomplete tumor killing when the freezing dose is not enough, which may lead to tumor recurrence or metastasis. Therefore, cryoablation combined with other therapeutic options is usually suggested to achieve a complete cure for lung cancer. Clinical practices have shown that traditional Chinese medicine (TCM) treatment can improve the quality of life of patients with advanced lung cancer and prolong the postoperative survival time. However, the mechanism of the synergistic effect of Chinese medicine and cryotherapy, and the optimal treatment plan have not been clarified so far. Therefore, the effect of TCM particles on ice crystal growth and phase transition during cooling was investigated. In addition, we explored the optimized concentration and combination treatment sequence of TCM (lung care formula) and validated the optimal treatment protocol by establishing a mouse model of non-small cell lung cancer (NSCLC). In general, cryoablation combined with TCM is a useful treatment for lung cancer, which can effectively solve the problem of tumor recurrence after cryoablation.

Role of MRI at 1- and 3-Month Follow-up in Predicting the Likelihood of Tumor Recurrence Following Percutaneous Cryoablation of Renal Tumors

PURPOSE

To evaluate whether ablation volume difference relatively to tumoral volume, minimal distance between ablation area and necrotic tumor, or apparent diffusion coefficient (ADC) within the ablation area, measured on 1- and 3-month follow-up MRI following cryoablation of renal tumors, are associated with tumor recurrence.

MATERIALS AND METHODS

136 renal tumors were retrospectively identified. Patients, tumor characteristics and follow-up MRI (1-, 3-, 6-month, and thereafter annually) were collected. Uni- and multivariate analyses were performed to assess the association between the investigated parameters and tumor recurrence.

RESULTS

Over the follow-up period (27.7 ± 21.9 months), 13 recurrences were identified at 20.5 ± 19.4 months. At 1- and 3-month, the mean volume difference between the ablation zone and the tumor volume were + 577.5 ± 511.3% vs + 251.4 ± 209.8% (p = 0.003), and + 268.8 ± 291.1% vs + 103.8 ± 94.6% (p = 0.023) in patients without and with tumor recurrence, respectively. At 1- and 3-month, the minimum distance between the necrotic tumor and the edge of the ablation area was 3.4 ± 2.5 vs 1.8 ± 1.9 mm (p = 0.019), and 2.4 ± 2.3 vs 1.4 ± 1.8 mm (p = 0.13) in patients without and with tumor recurrence, respectively. Analysis of ADC values was not associated with tumor recurrence. After performing the multivariate analysis, only volume difference of the ablation area compared to tumor volume was associated with absence of tumor recurrence at 1- (OR = 14.1; p = 0.001) and 3-month (OR = 8.2; p = 0.01).

CONCLUSIONS

Evaluation of volume difference between the ablation area and tumor volume on early (≤ 3 months) MRI follow-up identifies patients at risk of tumor recurrence.

Cryoablation and Immunotherapy: An Enthralling Synergy for Cancer Treatment

As less invasive options for surgical tumor removal, minimally invasive ablative techniques have gained popularity. Several solid tumors are being treated with cryoablation, a non-heat-based ablation technique. Cryoablation data in comparison over time demonstrates better tumor response and faster recovery. Combining cryosurgery with other cancer therapies has been explored to improve the cancer-killing process. Cryoablation with the combination of immunotherapy, results in a robust and efficient attack on the cancer cells. This article focuses on investigating the ability of cryosurgery to create a strong antitumor response when combined with immunologic agents resulting in a synergetic effect. To achieve this objective, we combined cryosurgery with immunotherapy using Nivolumab and lpilimumab. Five clinical cases of lymph node, lung cancer, bone, and lung metastasis were followed and analyzed. In this series of patients, percutaneous cryoablation and addressing immunity agents were technically feasible. In the follow-ups, there appeared to be no radiological evidence of new tumor development.

Radiofrequency Ablation, Cryoablation, and Microwave Ablation for the Treatment of Small Renal Masses: Efficacy and Complications

Over the last two decades the detection rate of small renal masses has increased, due to improving diagnostic accuracy, and nephron-sparing treatments have become the first-choice curative option for small renal masses. As a minimally invasive alternative, thermal ablation has increased in popularity, offering a good clinical outcome and low recurrence rate. Radiofrequency ablation, Cryoablation, and Microwave ablation are the main ablative techniques. All of them are mostly overlapping in term of cancer specific free survival and outcomes. These techniques require imaging study to assess lesions features and to plan the procedure: US, CT, and both of them together are the leading guidance alternatives. Imaging findings guide the interventional radiologist in assessing the risk of complication and possible residual disease after procedure. The purpose of this review is to compare different ablative modalities and different imaging guides, underlining the effectiveness, outcomes, and complications related to each of them, in order to assist the interventional radiologist in choosing the best option for the patient.

Tips and Tricks for Successful Percutaneous Cryoablation of Large Renal Cell Carcinomas

Percutaneous cryoablation has proved to be safe and effective for the treatment of stage T1a renal cell carcinoma (RCC). Patients with larger-sized RCCs may not be good surgical candidates or may have tumors located in anatomically unfavorable locations, which makes partial nephrectomy more challenging. In this patient population, percutaneous cryoablation can be considered a treatment option, given its less invasive nature when compared to surgery. The ablation of larger-sized RCCs requires careful planning to ensure that the tumor volume is completely covered within the ablation zone, while minimizing the risks of non-target injury to the surrounding critical organs. In this article, we share our institutional experience in treating larger-sized RCCs (> 4 cm) using percutaneous cryoablation alone. We discuss strategies to maximize the volume of the ablation zone through the precise placement of the probes. We also shed light on different techniques to protect the surrounding structures during cryoablation.

Assessing Trifecta Achievement after Percutaneous Cryoablation of Small Renal Masses: Results from a Multi-Institutional Collaboration

Background and Objectives: To assess efficacy and safety of Percutaneous Cryoablation (PCA) of small renal masses (SRMs) using Trifecta outcomes in a large cohort of patients who were not eligible for surgery. Materials and methods: All PCAs performed in four different centers between September 2009 and September 2019 were retrospectively evaluated. Patients were divided in two different groups depending on masses dimensional criteria: Group-A: diameter ≤ 25 mm and Group-B: diameter > 25 mm. Complications rates were reported and classified according to the Clavien−Dindo system. The estimate glomerular filtration rate (eGFR) was calculated before PCA and during follow-up schedule. Every patient received a Contrast Enhanced Ultrasound (CEUS) evaluation on the first postoperative day. Radiological follow-up was taken at 3, 6, and 12 months for the first year, then yearly. Radiological recurrence was defined as a contrast enhancement persistence and was reported in the study. Finally, Trifecta outcome, which included complications, RFS, and preservation of eGFR class, was calculated for every procedure at a median follow-up of 32 months. Results: The median age of the patients was 74 years. Group-A included 200 procedures while Group-B included 140. Seventy-eight patients were eligible for Trifecta evaluation. Trifecta was achieved in 69.6% of procedures in Group-A, 40.6% in Group-B (p = 0.02). We observed an increased rate of complication in Group-B (13.0% vs. 28.6; p < 0.001). However, 97.5% were <II Clavien−Dindo grade. No differences were found between the two groups regarding eGFR before and after treatment. Further, 24-months RFS rates were respectively 98.0% for Group-A and 92.1% in Group-B, while at 36 months were respectively 94.5% and 87.5% (p = 0.08). Conclusions: PCA seems to be a safe and effective treatment for SRM but in the need of more strict dimensional criteria to achieve a higher possible success rate.

Highly efficient magnetic ablation and the contrast of various imaging using biocompatible liquid-metal gallium

Background

Although the powerful clinical effects of radiofrequency and microwave ablation have been established, such ablation is associated with several limitations, including a small ablation size, a long ablation time, the few treatment positioning, and biosafety risks. To overcome these limitations, biosafe and efficient magnetic ablation was achieved in this study by using biocompatible liquid gallium as an ablation medium and a contrast medium for imaging.

Results

Magnetic fields with a frequency (f) lower than 200 kHz and an amplitude (H) × f value lower than 5.0 × 10⁹ Am⁻¹ s⁻¹ were generated using the proposed method. These fields could generate an ablation size of 3 cm in rat liver lobes under a temperature of approximately 300 °C and a time of 20 s. The results of this study indicate that biomedical gallium can be used as a contrast medium for the positioning of gallium injections and the evaluation of ablated tissue around a target site. Liquid gallium can be used as an ablation medium and imaging contrast medium because of its stable retention in normal tissue for at least 3 days. Besides, the high anticancer potential of gallium ions was inferred from the self-degradation of 100 µL of liquid gallium after around 21 days of immersion in acidic solutions.

Conclusions

The rapid wireless ablation of large or multiple lesions was achieved through the simple multi-injection of liquid gallium. This approach can replace the currently favoured procedure involving the use of multiple ablation probes, which is associated with limited benefits and several side effects.

Methods

Magnetic ablation was confirmed to be highly efficient by the consistent results obtained in the simulation and in vitro tests of gallium and iron oxide as well as the electromagnetic specifics and thermotherapy performance comparison detailed in this study Ultrasound imaging, X-ray imaging, and magnetic resonance imaging were found to be compatible with the proposed magnetic ablation method. Self-degradation analysis was conducted by mixing liquid gallium in acidic solutions with a pH of approximately 5–7 (to imitate a tumour-containing microenvironment). X-ray diffraction was used to identify the gallium oxides produced by degraded gallium ions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12938-022-01003-9.

Correlation between renal ablation zone in contrast-enhanced CT and non-enhanced MRI during the early period following percutaneous cryoablation

Purpose

To retrospectively evaluate and correlate the contrast-enhanced computed tomography (CECT) and non-enhanced magnetic resonance imaging (MRI) during the early period following renal cryoablation.

Materials and methods

Both dynamic CECT and non-enhanced MRI were performed within 4 days following cryoablation in 34 renal tumors in 33 patients. The renal volumes of the unenhanced regions on dynamic CECT (nephrogenic phase, 4 mm thickness) and the regions with signal intensity changes on non-enhanced MRI (fat-suppressed T2-weighted image, 4 mm thickness) were evaluated. Fusion images of the axial, coronal, and sagittal sections of CECT and MRI images were created from the maximum cross-section of the renal tumor, and the match score of each image was visually evaluated on a 5-point scale.

Results

The mean renal volume of the unenhanced regions on CECT and those with signal intensity changes on non-enhanced MRI following cryoablation were 29.5 ± 19.9 cm³ (range, 4.3–97.4 cm³) and 30.7 ± 19.8 cm³ (range, 6.7–94.0 cm³), respectively; the difference between them was –1.17 cm³ (95% confidence interval [CI] –2.74, 0.40, P = 0.139). The Pearson’s product-moment correlation coefficient (r = 0.975; 95% CI, 0.951, 0.988; P < 0.0001) showed a strong correlation between the volumes. The average match score between CECT and non-enhanced MRI was as high as 4.5 ± 0.5 points (radiologist 1, 4.3 ± 0.5; radiologist 2, 4.7 ± 0.5). Local tumor control rate was 94.1% (32/34 tumors) and recurrence-free survival rate was 82.0% (95% CI: 64.2%, 91.5%) at 5 years.

Conclusions

The region with signal intensity changes on non-enhanced MRI was strongly correlated with the unenhanced region on CECT during the early period following renal cryoablation.

Comparison of Radiofrequency Ablation Versus Cryoablation For T1 Renal Tumors: An Evidence-Based Analysis of Comparative Outcomes

Objective

To discuss the differences in the effectiveness and security for T1 renal tumors by radiofrequency ablation (RFA) and cryoablation (CA).

Methods

We systematically searched the Cochrane Library, PubMed, Embase, CNKI databases, and Science databases, and the date was from the above database establishment to August 2021. Controlled trials on RFA and CA for T1 renal tumors were included. The meta-analysis was conducted with the Review Manager 5.4 software.

Results

A total of ten studies with 2,367 patients were included in the analysis. There were no significant differences in complications (odds ratio [OR], 1.23; 95% CI, 0.80 to 1.90; p=0.35), primary technique efficacy rate (OR, 1.01; 95% CI, 0.33 to 3.14; p=0.98), changes in serum creatinine (weighted mean difference [WMD], 0.53; 95% CI, -0.50 to 1.57; p=0.31), or 5-year survival rate (hazard ratio [HR], 1.11; 95% CI, 0.41 to 3.00; p=0.84) among patients undergoing RFA and CA. However, compared with patients who underwent RFA, patients who underwent CA had a lower Local recurrence (OR: 2.25; 95% CI: 1.38 to 3.67; p = 0.001).

Conclusion

The analysis demonstrated that in the treatment of T1 renal tumors, CA may be associated with lower local recurrence rates. However, no differences were observed in terms of primary technique efficacy rate, 5-year survival rate, changes in serum creatinine, and complication rate between groups.

Systematic Review Registration

[https://www.crd.york.ac.uk/PROSPERO/], identifier PROSPERO (CRD42021295160).

Percutaneous Cryoablation of Renal Tumors: Initial Indian Experience

Objective The purpose of this study was to report short-term outcomes of cryoablation of early-stage renal tumors (T1a and T1b) at a tertiary hospital in India.

Methods This was a retrospective study of consecutive patients who underwent cryoablation for renal cell carcinoma (RCC) from November 2018 to June 2020. Cryoablation was performed under combined ultrasound and computed tomography guidance using a helium-argon cryoablation system. Tumor number, size, location, nephrometry score, relationship of the tumor with pelvicalyceal system, and adjacent organs were tabulated, and technical and clinical success evaluated. Early and late recurrence and complications were also assessed.

Results Eleven patients (median age: 62 years) with 11 tumors underwent cryoablation. The mean tumor size was 2.58 cm (range: 1.62–5.62 cm) with 10 lesions being T1a and one lesion T1b. Tissue sampling was done in 9/11 patients, 3 were papillary RCC and the rest, clear cell RCC. In two patients, the tumor was completely endophytic, three patients had partially endophytic tumors while 6 patients had exophytic lesions. The median nephrometry score was 6 (range: 4–11, Mode 4). Technical success was achieved in all patients. Complete response was achieved in 81% (9/11) of the patients at 1-month follow-up. Median follow-up period was 6 months. Two patients showed residual disease on follow-up imaging at 1 and 3 months, respectively.

Conclusion Cryoablation is a promising, relatively new minimally invasive therapy for treating small renal tumors in India. It is safe, technically feasible, and shows excellent short-term efficacy.

Imaging considerations for thermal and radiotherapy ablation of primary and metastatic renal cell carcinoma

Ablative (percutaneous and stereotactic) thermal and radiotherapy procedures for management of both primary and metastatic renal cell carcinoma are increasing in popularity in clinical practice. Data suggest comparable efficacy with lower cost and morbidity compared to nephrectomy. Ablative therapies may be used alone or in conjunction with surgery or chemotherapy for treatment of primary tumor and metastatic disease. Imaging plays a crucial role in pre-treatment selection and planning of ablation, intra-procedural guidance, evaluation for complications, short- and long-term post-procedural surveillance of disease, and treatment response. Treatment response and disease recurrence may differ considerably after ablation, particularly for stereotactic radiotherapy, when compared to conventional surgical and chemotherapies. This article reviews the current and emerging role of imaging for ablative therapy of renal cell carcinoma.

Complications of renal interventions: a pictorial review of CT findings

A number of potential vascular and non-vascular complications can arise from surgical, extracorporeal shock wave lithotripsy, radiotherapy and radiological renal interventions, including percutaneous image-guided biopsy and drainage. Computed tomography scan is usually one of the first and most important diagnostic imaging examinations requested when a potential complication is suspected. There are a wide range of common and uncommon potential complications from renal interventions. An understanding of underlying risk factors is important to reduce potential complications from renal intervention. Radiologists play a crucial role in recognising and diagnosing post-renal intervention complications on computed tomography scans, which could significantly improve the patient’s prognosis.

Percutaneous CT-Guided Renal Cryoablation: Technical Aspects, Safety, and Long-Term Oncological Outcomes in a Single Center

Background and objectives: Cryoablation is emerging as a safe and effective therapeutic option for treating renal cell carcinoma. This study analyzed the safety and long-term oncological outcomes of cryoablation in our center. Materials and methods: Patients who underwent computed tomography (CT)-guided percutaneous cryoablation between February 2011 and June 2020 for one or more clinically localized renal tumors were identified. Technical success and treatment efficacy were assessed. Post-procedural complications were classified according to the Clavien-Dindo system. Recurrence-free survival was determined for biopsy-proven malignant renal tumors. Results: A total of 174 renal tumors, 78 of which were biopsy-proven malignant carcinomas, were treated in 138 patients (97 males and 41 females, mean age: 73 years, range: 43-89 years). Mean tumor size was 2.25 cm and 54.6% of the lesions required a complex approach. Technical success was achieved in 171 out of 174 tumors (98.3%). Primary treatment efficacy was 95.3% and increased to 98.2% when retreats were taken into account. The overall complication rate was 29.8%. No complications of Clavien-Dindo grade III or more were encountered. Median follow-up was 21.92 months (range: 0.02-99.87). Recurrence-free survival was 100% at 1 year, 95.3% (95% CI: 82.1%-98.8%) at 3 years, and 88.6% (95% CI: 71.8%-95.7%) at 5 years. Conclusions: Cryoablation is a safe and effective technique for the treatment of small renal lesions, with no major complications when performed by expert interventional radiologists. The multidisciplinary discussion is essential, especially considering the high number of histologically undetermined lesions. Our long-term oncological outcomes are encouraging and in line with the literature.

Irreversible Electroporation for Renal Ablation Does Not Cause Significant Injury to Adjacent Ureter or Bowel in a Porcine Model

Objective: To evaluate the safety of irreversible electroporation (IRE) for renal ablation adjacent to the ureter or bowel. Materials and Methods: Six adult pigs each underwent bilateral IRE of the kidney. To simulate adjacence, the left proximal ureter and duodenum were secured onto the left and right kidney capsule, respectively. Two IRE probes were placed into the renal parenchyma and configured to bridge the ureter and bowel. Therapeutic IRE was delivered at 2000 V/cm for 70 pulses in both forward and reverse polarity. The animal was survived and euthanized at 1, 3, or 14 days. Histopathology was obtained for all potentially injured bowel and ureteral segments. Retrograde pyelogram (RPG) was performed on each left-sided ureter. Results: Histologic analysis of the ureter identified reactive changes at the level of the periureteral adipose tissue, which progressed from acute inflammation on day 1 to focal fibrosis by day 14. Urothelial mucosa and surrounding smooth muscle layers were unaffected at all time points. RPGs did not show any abnormalities in all specimens. Histologic analysis of the bowel demonstrated acute inflammation in the serosa and subserosal tissue on day 1. Three days after IRE, inflammation and crypt abscesses were focally present in the deep aspects of the bowel mucosa. Inflammation in the mucosal layer resolved 14 days after IRE. Conclusions: In a porcine model of renal IRE, no significant injury was apparent after intentional ablation adjacent to the ureter and bowel. IRE may be a safe alternative to thermal ablation for tumors near the ureter or bowel.

Renal mass cryoablation: Melting time analysis of radiographic ice-ball after 5-minute active thawing by using serial ultrasound

OBJECTIVE

Cryoneedles removal before sufficient thawing may lead to tissue damage and bleeding. We analyzed melting time of radiographic ice-ball in renal percutaneous cryoablation (PCA) using ultrasound.

MATERIALS AND METHODS

Consecutive 27 patients who underwent PCA using cryoneedles of 2-4 for the renal mass (median size, 1.9 cm; range, 1.1-4.1 cm) were evaluated. Reconstructed CT images obtained during freezing were used to measure radiographic ice-ball volume. After completing final freezing, 5-min active thawing and following passive thawing were performed. Melting time of radiographic ice-ball during the thawing was analyzed by serial ultrasound examination. Melting time was defined as the time of complete disappearance of intrarenal posterior acoustic shadowing generated by radiographic ice-ball, which was analyzed by two independent radiologists. The relationship between total melting time and radiographic ice-ball volume was also analyzed by Spearman's rank correlation.

RESULTS

Median radiographic ice-ball volume was 30.5 cm³ (range, 26.6-37.3 cm³). After 5-min active thawing, radiographic ice-ball needed additional passive thawing of median 8-min or 9-min for complete melting in analyses of two independent radiologists, respectively (p > 0.05). The range of total melting time during active and passive thawing was 9-min-to-15-min for both radiologists, respectively. A positive correlation was found between total melting time and radiographic ice-ball volume (Spearman's rho, 0.644 and 0.479 for radiologist 1 and 2).

CONCLUSION

In our PCA protocol, radiographic ice-ball needed approximately 10-min passive thawing after 5-min active thawing for complete melting. This may help determine safe removal time of cryoneedles.

Validation of a Web-Based Planning Tool for Percutaneous Cryoablation of Renal Tumors

Purpose

To validate a simulation environment for virtual planning of percutaneous cryoablation of renal tumors.

Materials and Methods

Prospectively collected data from 19 MR-guided procedures were used for validation of the simulation model. Volumetric overlap of the simulated ablation zone volume (Σ) and the segmented ablation zone volume (S; assessed on 1-month follow-up scan) was quantified. Validation metrics were DICE Similarity Coefficient (DSC; the ratio between twice the overlapping volume of both ablation zones divided by the sum of both ablation zone volumes), target overlap (the ratio between the overlapping volume of both ablation zones to the volume of S; low ratio means S is underestimated), and positive predictive value (the ratio between the overlapping volume of both ablation zones to the volume of Σ; low ratio means S is overestimated). Values were between 0 (no alignment) and 1 (perfect alignment), a value > 0.7 is considered good.

Results

Mean volumes of S and Σ were 14.8 cm³ (± 9.9) and 26.7 cm³ (± 15.0), respectively. Mean DSC value was 0.63 (± 0.2), and ≥ 0.7 in 9 cases (47%). Mean target overlap and positive predictive value were 0.88 (± 0.11) and 0.53 (± 0.24), respectively. In 17 cases (89%), target overlap was ≥ 0.7; positive predictive value was ≥ 0.7 in 4 cases (21%) and < 0.6 in 13 cases (68%). This indicates S is overestimated in the majority of cases.

Conclusion

The validation results showed a tendency of the simulation model to overestimate the ablation effect. Model adjustments are necessary to make it suitable for clinical use.

Mimics and Pitfalls in Renal Imaging

There are several potential pitfalls that radiologists face when interpreting images of the kidneys. Some result from image acquisition and can arise from the imaging equipment or imaging technique, whereas others are patient related. Another category of pitfalls relates to image interpretation. Some difficulties stem from methods to detect enhancement after contrast administration, whereas others are benign entities that can mimic a renal tumor. Finally, interpretation and diagnosis of fat-containing renal masses may be tricky due to the complexities discerning the pattern of fat within a mass and how that translates to an accurate diagnosis.

Outcomes of Renal Tumors Treated by Image-Guided Percutaneous Cryoablation: Immediate and 3- and 5-Year Outcomes at a Regional Center

OBJECTIVE. The purpose of this study was to evaluate the immediate and 3- and 5-year outcomes of patients with clinical stage T1 (cT1) biopsy-proven renal cell carcinoma (RCC) treated by image-guided percutaneous cryoablation at a regional interventional oncology center. MATERIALS AND METHODS. A prospectively maintained local interventional radiology database identified patients with cT1 RCC lesions that were treated by percutaneous cryoablation. Technical success, procedural complications (graded using the Clavien-Dindo classification system), and the residual unablated tumor rate were collated. Local tumor progression-free survival was estimated using Kaplan-Meier estimates. RESULTS. A total of 180 patients with 185 separate cT1 RCC lesions were identified. Mean patient age was 68.4 years (range, 34.1-88.9 years) and 52 patients (28.9%) were women. There were 168 (90.8%) and 17 (9.2%) cT1a and cT1b lesions, respectively, with a mean lesion size of 28.5 mm (range, 11-58 mm). Technical success was achieved in 183 of 185 (98.9%) patients. The major complication rate (Clavien-Dindo classification ≥ grade III) was 2.2% (four out of 185). Residual unablated tumor on the first follow-up scan was identified in four of 183 tumors (2.2%). Estimated local tumor progression-free survival at 3 and 5 years was 98.3% and 94.9%, respectively. No distant metastases or deaths attributable to RCC occurred. Mean estimated glomerular filtration rate (eGFR) before the procedure was 72.4 ± 18.5 (SD) mL/min/1.73 m² and this was not statistically significantly different after the procedure (69.7 ± 18.8 mL/min/1.73 m²), at 1 year (70.7 ± 16.4 mL/min/1.73 m²), or at 2 years (69.8 ± 18.9 mL/min/1.73 m²) (p > 0.05). CONCLUSION. These data add to the accumulating evidence that image-guided cryoablation is an efficacious treatment for selected cT1 RCC with a low complication rate and ro bust 3- and 5-year outcomes.

Systematic Review of Contemporary Evidence for the Management of T1 Renal Cell Carcinoma: What IRs Need to Know for Kidney Cancer Tumor Boards

Renal cell carcinoma is a relatively common malignancy, with 60 to 70 thousand cases a year in the United States alone. Increased utilization of cross-sectional imaging has led to an increase in the number of early renal cell cancers seen by the medical establishment. In addition, certain patient populations have an increased risk of developing kidney cancers which may mandate aggressive screening protocols. This article discusses the epidemiology of renal cell cancers; discusses the current management guidelines from multiple specialty societies; discusses some of the surgical and interventional techniques used in the treatment of such lesions; and provides a review of the literature regarding treatments of early-stage renal cell cancers.

Imaging findings during and after percutaneous cryoablation of hepatic tumors

OBJECTIVE

Imaging plays a key role in the assessment of patients before, during, and after percutaneous cryoablation of hepatic tumors. Intra-procedural and early post-procedure imaging with CT and MRI is vital to the assessment of technical success including adequacy of ablation zone coverage. Recognition of the normal expected post-procedure findings of hepatic cryoablation such as ice ball formation, hydrodissection, and the normal appearance of the ablation zone is crucial to be able to differentiate from complications including vascular, biliary, or non-target organ injury. Delayed imaging is essential for determination of clinical effectiveness and detection of unexpected findings such as residual unablated tumor and local tumor progression. The purpose of this article is to review the spectrum of expected and unexpected imaging findings that may occur during or after percutaneous cryoablation of hepatic tumors.

CONCLUSION

Differentiating expected from unexpected findings during and after hepatic cryoablation helps radiologists identify residual or recurrent tumor and detect procedure-related complications.

The effectiveness of RENAL nephrometry score in ablated renal tumors via radiofrequency ablation or cryoablation

Background/aim

This study aimed to evaluate the clinical efficacy of radiofrequency ablation (RFA) and cryotherapy and to scrutinize the therapeutic success of the RENAL (radius, exophytic/endophytic, nearness to collecting system, anterior/posterior, and location) nephrometry score in terms of possible complications and the predictive status of oncological results.

Materials and methods

Forty-five patients with biopsy-proven renal cell carcinomas (32 males, 13 females) treated with RFA and cryotherapy were included. Patients were 22–90 years old (average: 59.2 years). Statistical analyses were performed using SPSS for Windows.

Results

A total of 79 lesions with dimensions varying between 0.9 and 4.5 cm (average: 2.2 cm) were ablated. Complete ablation was achieved for 72 (91.1%) lesions. Six repeat RFA sessions were applied for 4 (5%) lesions with residue/recurrence. The average RENAL nephrometry scores of lesions that underwent complete ablation and those that developed residue/recurrence were 6.3 and 7.7, respectively. The average recurrence-free survival time was 34.8 months (range: 3–55 months), while it was 44.6 months (range: 6–55 months) for cryotherapy and 28.6 months (range: 3–50 months) for RFA.

Conclusion

Ablative therapies are minimally invasive and effective methods for treating small renal tumors. RENAL nephrometry scoring is a valuable system for standardizing renal tumors and evaluating the success of ablative therapies, possible complications, and oncological results.

Percutaneous cryoablation for renal cell carcinoma using ultrasound-guided targeting and computed tomography-guided ice-ball monitoring: radiation dose and short-term outcomes

BACKGROUND

Usefulness of ultrasound (US)-guided mass targeting and computed tomography (CT)-guided ice-ball monitoring in percutaneous cryoablation (PCA) for renal cell carcinoma (RCC) is still uncertain.

PURPOSE

To assess radiation dose and short-term outcomes of PCA for RCC using US-guided targeting and CT-guided ice-ball monitoring.

MATERIAL AND METHODS

Thirty-nine consecutive patients who underwent PCA for biopsy-proven RCC were included. Mass targeting was performed with US and ice-ball was monitored with CT guidance. Effective radiation dose of CT during PCA was recorded. Follow-up was conducted with contrast-enhanced CT or magnetic resonance imaging (MRI) (mean follow-up time = 10.1 ± 7.0 months). Local tumor progression was defined by the presence of focal enhancing areas at the ablation zone (CT, ≥ 20 HU; MRI, presence of focal enhancement on subtraction contrast-enhanced image). Technical success, major complication rate (e.g. Clavien-Dindo classification ≥ 3), and one-year local tumor progression-free survival (PFS) rate were analyzed.

RESULTS

Mean effective radiation dose in association with PCA was 12.1 ± 4.5 mSv (range = 7.0-25.2 mSv). Technical success was achieved in 100%. Local tumor progression occurred in a single patient (2.6%, 1/39), and one-year local tumor PFS rate was 95.7%. No major complication was found.

CONCLUSION

PCA using US-guided targeting and CT-guided ice-ball monitoring may allow acceptable local tumor control for RCC, as a radiation-reducing strategy.

Pre-cryoablation Embolization of Renal Tumors: Decreasing Probes and Saving Loads

The use of adjuvant pre-ablation embolization for renal tumors has been reported in endophytic, centrally located lesions to reduce the risk of injuring the renal collecting system during subsequent cryoablation. In this technical report, we present another utilization of adjuvant pre-ablation embolization, applied for the purpose of decreasing the number of cryoablation probes needed in the ablation intervention. This novel procedural protocol not only decreases the cost of the procedure, but also preserves more normal renal parenchyma, and decreases the risk of injuries related to probe positioning.

Embolization-induced Renal Tumor Shrinkage Followed by Definitive Cryoablation

Significant incidental findings reported on computed tomography (CT) scans are common. This article describes a 72-year-old man evaluated for possible bowel obstruction in whom was found a 3.1-cm x 2.6-cm centrally located enhancing mass in the left kidney highly suspicious for renal cell carcinoma. Due to substantial medical comorbidities, the patient was deemed a poor surgical candidate for either partial or complete nephrectomy. Interventional radiology was consulted for a minimally invasive ablation procedure. The large size and central location of the tumor involving the renal collecting system initially precluded definitive percutaneous cryoablation. Intra-arterial embolization was used as neoadjuvant therapy to decrease tumor burden. Fluoroscopy-guided bland embolization was performed targeting the arterial supply of the mass until stagnation of flow was achieved. A subsequent two-month post-embolization follow-up CT scan showed a 30% reduction in tumor size. Shrinkage of the mass from a central to a more peripheral location allowed for a cryoablation approach that would avoid damage to the vulnerable collecting system. Cryoablation was performed, and intraoperative CT demonstrated complete coverage of the tumor by the ice ball with no damage to the renal collecting system. A follow-up CT scan four years later showed no residual malignancy at the ablation site.

The "Lightning bolt" Sign on Computed Tomography during Percutaneous Renal Mass Cryoablation

Ice-ball fracture is a rare and often overlooked entity that may lead to intraprocedural hemorrhage after percutaneous cryoablation of renal masses. There is scant literature on ice-ball fractures associated with percutaneous renal cryoablation. Immediate recognition of the lightning bolt sign during intraprocedural computed tomography can help identify patients who may have developed this complication.

Image-Guided Renal Interventions

Image-guided renal biopsies have an increasing role in clinical practice. Renal mass and renal parenchymal biopsy indications, techniques, and other clinical considerations are reviewed in this article. Image-guided renal mass ablation shows significant promise and increasing clinical usefulness as more studies demonstrate its safety and efficacy. Renal mass ablation indications, techniques, and other considerations are also reviewed.

Image-guided minimally invasive treatment for small renal cell carcinoma

Surgical partial nephrectomy is still considered as the "gold standard" for the definitive management of small malignant renal masses, whereas treatment with image-guided percutaneous ablation is still mainly reserved for those patients who cannot undergo nephron-sparing surgical resection due to advanced age, underlying comorbidities or compromised renal function. Nonetheless, the recent evidence that underlines the long-term oncological equipoise of percutaneous ablation methods with surgical resection in combination with the reduced complication rate and cost supports the use of an image-guided minimally invasive approach as a first-line treatment. The purpose of this review is to offer an overview of the most widely used percutaneous renal ablation treatments (radiofrequency, microwave and cryoablation) with a focus on their main technical aspects and application techniques for curative ablation of small renal cell carcinoma (stage cT1a). The authors also provide a critical narrative of the relevant medical literature with an emphasis on outcomes of comparative effectiveness research, and appraise the percutaneous methods compared to surgery in the context of evidence-based practice and future research studies.

TEACHING POINTS

• RCC is a common cancer and is increasingly detected incidentally at early stages. • There is long-term oncological equipoise of percutaneous ablation compared to surgical resection. • Large-scale trials are required to produce Level 1a evidence.

Assessing the Effect of Weight-Based Protocol Modifications to Lower Dose for CT-Guided Hepatic and Renal Tumor Radiofrequency Ablations

OBJECTIVE

This study assessed radiation dose after CT-guided percutaneous radiofrequency ablations (RFAs) of hepatic and renal tumors and the effect of weight-based CT protocol modification for lowering overall dose in these procedures.

MATERIALS AND METHODS

CT-guided RFA for renal and hepatic ablations performed from January 1, 2009, through December 31, 2009, were retrospectively reviewed (90 men and 48 women; age, 42-81 years). The radiation dose was recorded during each of the following steps: planning, performing, and postprocedure. Weight-based protocol modification changes in tube voltage and tube current were then applied to renal and hepatic ablations performed subsequently (18 men and 11 women; age, 48-82 years). Image quality, needle localization, lesion detection, ability to detect complications, and overall operator satisfaction were noted for each case (score, 1-5). Dose reduction after modification was then calculated.

RESULTS

Retrospective analysis found a mean (± SD) overall CT dose index (CTDI) for CT-guided RFA to be 16.5 ± 2.3 mGy. After protocol modification, the mean CTDI decreased to 6.63 ± 0.67 mGy, a 59.6% reduction overall; for hepatic ablations, the reduction was 65.96% (p < 0.0001) and the reduction for renal ablations was 38.97% (p = 0.0153). Image quality analysis showed high operator satisfaction (3-5), including adequate needle localization (4-5), lesion visibility (3-5), and high performer confidence (4-5). Higher dose reduction was noted for patients weighing more than 180 lb (82 kg) (p < 0.0001).

CONCLUSION

Simple weight-based CT protocol modifications can significantly reduce radiation dose during CT-guided percutaneous ablations in the liver and kidneys without significantly sacrificing image quality.

[Percutaneous renal ablation: Pre-, per-, post-interventional evaluation modalities and adapted management]

OBJECTIVES

Ablative treatment (AT) rise is foreseen, validation of steps to insure good proceedings is needed. By looking over the process of the patient, this study evaluates the requirements and choices needed in every step of the management.

METHODS

We searched MEDLINE^®, Embase^®, using (MeSH) words and we looked for all the studies. Investigators graded the strength of evidence in terms of methodology, language and relevance.

RESULTS

Explanations of AT proposal rather than partial nephrectomy or surveillance have to be discussed in a consultation shared by urologist and interventional radiologist. Per-procedure choices depend on predictable ballistic difficulties. High volume, proximity of the hilum or of a risky organ are in favor of general anesthesia, cryotherapy and computed tomography/magnetic resonance imaging (CT/MRI). Percutaneous approach should be privileged, as it seems as effective as the laparoscopic approach. Early and delayed complications have to be treated both by urologist and radiologist. Surveillance by CT/MRI insure of the lack of contrast-enhanced in the treated area. Patients and tumors criteria, in case of incomplete treatment or recurrence, are the key of the appropriate treatment: surgery, second session of AT, surveillance.

CONCLUSION

AT treatments require patient's comprehension, excellent coordination of the partnership between urologist and radiologist and relevant choices during intervention.

Focal ablation therapy for renal cancer in the era of active surveillance and minimally invasive partial nephrectomy

Partial nephrectomy is the optimal surgical approach in the management of small renal masses (SRMs). Focal ablation therapy has an established role in the modern management of SRMs, especially in elderly patients and those with comorbidities. Percutaneous ablation avoids general anaesthesia and laparoscopic ablation can avoid excessive dissection; hence, these techniques can be suitable for patients who are not ideal surgical candidates. Several ablation modalities exist, of which radiofrequency ablation and cryoablation are most widely applied and for which safety and oncological efficacy approach equivalency to partial nephrectomy. Data supporting efficacy and safety of ablation techniques continue to mature, but they originate in institutional case series that are confounded by cohort heterogeneity, selection bias, and lack of long-term follow-up periods. Image guidance and surveillance protocols after ablation vary and no consensus has been established. The importance of SRM biopsy, its optimal timing, the type of biopsy used, and its role in treatment selection continue to be debated. As safety data for active surveillance and experience with minimally invasive partial nephrectomy are expanding, the role of focal ablation therapy in the treatment of patients with SRMs requires continued evaluation.

Percutaneous US-guided renal cryoablation using 3D modeling

INTRODUCTION

The article describes the first experience of performing percutaneous ultrasound (US)-guided cryoablation of renal tumor and assesses the safety and short-term results of treatment.

MATERIALS AND METHODS

Twelve patients were subjected to US-guided cryoablation of renal tumor in 2015. The tumor size in 11 patients was up to 3.0 cm (T1а); in one female patient, 4.5 cm (T1b). Tumors were assessed according to the PADUA score. In eight patients, it was 6-7 (low); in three patients, 8-9 (average); in one, 10 (high). All the patients underwent US examination using a FlexFocus 800 apparatus with convex abdominal transducers. Before surgery and 6 months later, all the patients underwent renal Doppler US and contrast-enhanced computed tomography.

RESULTS

The average cryoablation time was 60 min. Seven operations were performed under spinal anesthesia and five operations under local anesthesia. The follow-up period lasted 8 months on average. According to the ultrasonography and Doppler findings, after 6 months, the tumor (T1a) in 11 patients reduced in size by an average of 7-8 mm and had no blood supply.T1b patient's mass size reduces from 4.5 to 3.7 cm; however, a 1.5 cm area with a high attenuation gradient of the contrast medium was visualized. Later, the patient was subjected to laparoscopic renal resection. Histological finding revealed clear-cell carcinoma.

CONCLUSIONS

We consider percutaneous US-guided cryoablation as a method of choice for patients with stage T1a renal tumor localized on the posterior or lateral surface in the inferior or middle segment without sinus involvement and PADUA <9.

Ultrasound-guided genitourinary interventions: principles and techniques

Ultrasound (US) is often used to guide various interventional procedures in the genitourinary (GU) tract because it can provide real-time imaging without any radiation hazard. Moreover, US can clearly visualize the pathway of an aspiration or biopsy needle to ensure the safety of the intervention. US guidance also helps clinicians to access lesions via the transabdominal, transhepatic, transvaginal, transrectal, and transperineal routes. Hence, US-guided procedures are useful for radiologists who wish to perform GU interventions. However, US-guided procedures and interventions are difficult for beginners because they involve a steep initial learning curve. The purpose of this review is to describe the basic principles and techniques of US-guided GU interventions.

Image-guided ablation of renal cell carcinoma

This review article aims to provide an overview of image-guided ablation of renal cell carcinoma (RCC) since it was first introduced in 1998. This will cover the background and rationale behind its development; an overview of the evidence for current thermal technology, such as heat-based, e.g., radiofrequency ablation (RFA), microwave ablation (MWA), and cold-based energies, e.g., cryoablation used; and summarise the published evidence regarding its treatment efficacy and oncological outcome. In addition, it aims to provide an insight into the potential role of the new non-thermal ablative technology, e.g., irreversible electroporation (IRE)/Nanoknife in image-guided ablation of RCC, as well as areas of challenge that will require further research and clinical evaluation to ensure delivery of a quality patient-centred interventional oncology (IO) service in image-guided ablation of RCC.

Contemporary Status of Percutaneous Ablation for the Small Renal Mass

Renal cell carcinoma is the tenth most common malignancy in the USA, with upwards of 61,000 new cases and resulting in more than 14,000 deaths annually. Although partial nephrectomy remains the standard treatment, image-guided nephron-sparing ablative techniques including cryoablation, radiofrequency ablation, and microwave ablation have emerged as treatment options in certain patient populations. Ablative therapies have high technical successes, low tumor recurrence rates, and preserve renal parenchymal volume. The purpose of this article is to provide an update on ablation therapies for small renal masses.

Evolutionary magnetic resonance appearance of renal cell carcinoma after percutaneous cryoablation

Objective:

To determine the evolutionary MRI appearance of renal cell carcinoma (RCC) following cryoablation.

Methods:

For this institution review board-approved study, we recruited patients with biopsy-proven RCC and treated them with percutaneous cryoablation between November 2009 and October 2014. Two radiologists retrospectively reviewed the pre-procedural and follow-up MRI. The findings included tumour sizes, signal intensities on T₁ weighted imaging (T1WI), T₂ weighted imaging (T2WI), diffusion-weighted imaging, apparent diffusion coefficient (ADC) map and contrast enhancement patterns. The ADC values of the tumours before and after treatment were measured.

Results:

A total of 26 patients were enrolled. The ablated tumours exhibited predominantly high signals on T1WI at 1–9-month follow-up (47.1% strong hyperintense at 3 months) and subsequently returned to being isointense. In T2WI, the signals of the ablated tumours were highly variable during the first 3 months and became strikingly hypointense after 6 months (58.3% strong hypointense at 6 months). Diffusion restriction was prominent during the first 3 months (lowest ADC: 0.62 ± 0.29 × 10⁻³ mm² s⁻¹ at 1 month). Contrast enhancement persisted up to 6 months after the procedure. The residual enhancement gradually increased in the dynamic scan and was most prominent in the delay phase.

Conclusion:

The MRI of the cryoablated renal tumour follows a typical evolutionary pattern.

Advances in knowledge:

Familiarity of practitioners with the normal post-cryoablation change of RCC on MRI can enable the early detection and prevention of tumour recurrence.

Percutaneous computed tomography-guided cryoablation for recurrent retroperitoneal soft tissue sarcoma: a study of safety and efficacy

AIMS

To evaluate the use of computed tomography image-guided percutaneous cryoablation for recurrent retroperitoneal soft tissue sarcomas (RPSs).

RESULTS

Adverse events were limited to grades 1 and 2, included fever (n = 19), local pain (n = 11), emesis (n = 10), frostbite (n = 6), and nerve injury (n = 1). Fever was more frequent in the large tumor group (15.8%) than in small tumor group (1.9%) (P = 0.008). Median PFS and OS were 37.0 ± 7.7 months (range, 4-39 months) and 43.0 ± 5.9 months (range, 6-54 months), respectively. PFS and OS were significantly longer in the small tumor group than in the large tumor group (P = 0.011 and P = 0.015, respectively), but the response rate (82.7% vs. 72.8%, P = 0.240) did not differ significantly. On univariate analysis, tumor size, tumor invasion grade, and distant metastasis were significant prognostic factors for PFS and OS. On multivariate analysis, a tumor size ≥10 cm was an independent negative prognostic factor for PFS and OS after cryoablation (HR: 3.98, 95% CI: 1.27-12.50, P = 0.018 and HR: 4.33, 95% CI: 1.41-13.26, P = 0.010, respectively).

MATERIALS AND METHODS

Data from 72 patients with recurrent RPSs who underwent percutaneous cryoablation were reviewed retrospectively. The prognostic factors for progression-free survival (PFS), overall survival (OS), and efficacy based on mRECIST criteria were analysis. Adverse events were compared according to tumor size (<10 and ≥10 cm).

CONCLUSION

Minimally invasive percutaneous cryoablation was safe and efficacious for recurrent RPSs.

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.

Minimally Invasive Percutaneous Treatment of Small Renal Tumors with Irreversible Electroporation: A Single-Center Experience

PURPOSE

To evaluate whether irreversible electroporation (IRE) can be used as an ablation technique for small renal tumors (T1a cancers or small benign tumors) and to describe features after ablation on computed tomography (CT) or magnetic resonance (MR) imaging.

MATERIALS AND METHODS

In this retrospective study, 20 patients (mean age, 65 y ± 12.8 y) underwent CT-guided IRE of T1a renal carcinoma (n = 13) or small benign or indeterminate renal masses < 4 cm in size (n = 7). Mean tumor size was 2.2 cm ± 0.7. The ablation area was verified with contrast-enhanced imaging performed immediately after the procedure to determine technical success. Imaging was performed 6 weeks (20 of 20 patients), 6 months (15 of 20), and 12 months (6 of 20) after ablation. Medical records and CT/MR imaging features of all patients were reviewed for recurrence, symptoms, and complications after treatment.

RESULTS

Technical success was achieved in all patients (100%); there were no major procedure-related complications. Minor complications occurred in 7 patients, including self-limiting perinephric hematomas, pain difficult to control, and urinary retention. Mean procedure time was 2.0 hours ± 0.7. At 6 weeks, 2 patients required salvage therapy because of incomplete ablation. At 6 months, all 15 patients with imaging studies available had no evidence of recurrence. At 1 year, 1 patient (1 of 6) was noted to have experienced recurrence. CT/MR imaging after IRE ablation demonstrated an area of nonenhancement in the treatment zone that involuted over ~6 months.

CONCLUSIONS

Renal IRE appears to be a safe treatment for small renal tumors. Tumors treated with IRE demonstrated nonenhancement in the treatment zone with involution on follow-up CT/MR imaging.