Combined embolization and percutaneous radiofrequency ablation of a solid renal tumor

Transarterial embolization of T1b and T2a renal cell carcinoma prior to percutaneous cryoablation: a retrospective comparative study

PURPOSE

To compare outcomes in patients with T1b and T2a renal cell carcinoma (RCC) treated with percutaneous cryoablation (PCA) who underwent transarterial embolization (TAE) of the RCC prior to PCA (TAE + PCA) to patients who were treated with PCA alone.

METHODS

Retrospective review of all adult patients with T1b (4.1-7 cm) and T2a (7.1-10 cm) RCC treated with PCA from 2008 to 2021. Data collected included age, sex, tumor diameter, RENAL nephrometry score, technical success, adverse events (AEs), changes in serum creatinine, local control, and recurrence rates. A p value of 0.05 was considered the threshold for statistical significance.

RESULTS

13 patients with 13 RCCs (mean age: 72.7 ± 10.4; 54% male) and 35 patients with 37 RCCs (mean age: 66.7 ± 10.6; 60% male) were included in the TAE + PCA and PCA groups, respectively. The TAE + PCA group had larger mean tumor diameter (5.7 ± 1.1 cm vs. 4.7 ± 0.6 cm; p < 0.0001) and higher mean RENAL nephrometry score (8.9 ± 1.1 vs. 7.8 ± 1.5; p = 0.02). There were no differences between the groups with respect to technical success of PCA (p = 0.46), local tumor control (p = 0.3), or mean number of procedures to achieve local tumor control (p = 0.85). Mean increase in serum creatinine was not significantly different between the two groups (p = .63). Major AEs were similar between the groups (p = 1); however, the TAE + PCA group had no major hemorrhagic AEs while the PCA alone group had three (8.3%).

CONCLUSION

TAE + PCA in patients with T1b or T2 RCC is technically feasible without significant added detriment to renal function. This combined approach may help to reduce hemorrhagic AEs but larger patient cohorts are needed.

Selective Arterial Embolization with N-Butyl Cyanoacrylate Prior to CT-Guided Percutaneous Cryoablation of Kidney Malignancies: A Single-Center Experience

The study’s purpose was to assess the safety, feasibility and efficiency of selective arterial embolization (SAE) using N-butyl cyanoacrylate (NBCA) glue before percutaneous cryoablation (PCA) of renal malignancies in patients whose tumor characteristics and/or comorbidities resulted in an unacceptable risk of bleeding. In this single-center retrospective study of 19 consecutive high-risk patients (median age, 74 years) with renal malignancies managed in 2017–2020 by SAE with NBCA followed by PCA, data about patients, tumor and procedures characteristics, complications, renal function and hemoglobin concentration before and after treatment, as well as recurrence were collected. Charlson comorbidity index was ≥4 in 89.5% of patients. Ten patients were treated by antiplatelet and/or anticoagulant therapy. Median tumor largest diameter was 3.75 cm (range, 1–6.5 cm) and R.E.N.A.L. nephrometry score was ≥7 in 80%, indicating substantial tumor complexity. No major complications were recorded and minor complications occurred in 7 patients. No residual tumor was found at 6-week imaging follow-up in 18/19 patients. Tumor recurrence was visible in 1/16 patients at 6-month imaging follow-up. No significant difference was found for renal function after treatment (p = 0.07), whereas significant decrease in hemoglobin concentration was noted (p = 0.00004), although it was relevant for only one patient who required only blood transfusion and no further intervention. SAE prior to PCA is safe and effective for managing renal malignancies in high-risk patients.

Deformable motion compensation for interventional cone-beam CT

Image-guided therapies in the abdomen and pelvis are often hindered by motion artifacts in cone-beam CT (CBCT) arising from complex, non-periodic, deformable organ motion during long scan times (5-30 s). We propose a deformable image-based motion compensation method to address these challenges and improve CBCT guidance. Motion compensation is achieved by selecting a set of small regions of interest in the uncompensated image to minimize a cost function consisting of an autofocus objective and spatiotemporal regularization penalties. Motion trajectories are estimated using an iterative optimization algorithm (CMA-ES) and used to interpolate a 4D spatiotemporal motion vector field. The motion-compensated image is reconstructed using a modified filtered backprojection approach. Being image-based, the method does not require additional input besides the raw CBCT projection data and system geometry that are used for image reconstruction. Experimental studies investigated: (1) various autofocus objective functions, analyzed using a digital phantom with a range of sinusoidal motion magnitude (4, 8, 12, 16, 20 mm); (2) spatiotemporal regularization, studied using a CT dataset from The Cancer Imaging Archive with deformable sinusoidal motion of variable magnitude (10, 15, 20, 25 mm); and (3) performance in complex anatomy, evaluated in cadavers undergoing simple and complex motion imaged on a CBCT-capable mobile C-arm system (Cios Spin 3D, Siemens Healthineers, Forchheim, Germany). Gradient entropy was found to be the best autofocus objective for soft-tissue CBCT, increasing structural similarity (SSIM) by 42%-92% over the range of motion magnitudes investigated. The optimal temporal regularization strength was found to vary widely (0.5-5 mm^-2) over the range of motion magnitudes investigated, whereas optimal spatial regularization strength was relatively constant (0.1). In cadaver studies, deformable motion compensation was shown to improve local SSIM by ∼17% for simple motion and ∼21% for complex motion and provided strong visual improvement of motion artifacts (reduction of blurring and streaks and improved visibility of soft-tissue edges). The studies demonstrate the robustness of deformable motion compensation to a range of motion magnitudes, frequencies, and other factors (e.g. truncation and scatter).

Update of Radiofrequency Ablation for Treating Benign and Malignant Thyroid Nodules. The Future Is Now

Thermal and chemical ablation are minimally invasive procedures that avoid removal of the thyroid gland and target symptomatic nodules directly. Internationally, Radiofrequency ablation (RFA) is among one of the most widely used thermal ablative techniques, and is gaining traction in North America. Surgery remains the standard of care for most thyroid cancer, and in the right clinical setting, Active Surveillance (AS) can be a reasonable option for low risk disease. Minimally invasive techniques have emerged as an alternative option for patients deemed high risk for surgery, or for those patients who wish to receive a more active treatment approach compared to AS. Herein, we review the literature on the safety and efficacy of RFA for treating benign non-functioning thyroid nodules, autonomously functioning thyroid nodules, primary small low risk thyroid cancer (namely papillary thyroid cancer) as well as recurrent thyroid cancer.

Novel Approaches for Treating Autonomously Functioning Thyroid Nodules

Benign thyroid nodules are exceedingly common in the adult population. Only a small percentage of nodules are toxic or autonomously functioning thyroid nodules (AFTNs). The options clinicians have for treating the symptoms of hyperthyroidism include anti-thyroidal medications, radioactive iodine, or surgery. Depending on the patient population treated, these options may not be suitable or have inherent risks that are undesirable to the patient. On the other hand, untreated hyperthyroidism can lead to osteoporosis, atrial fibrillation, emotional lability, and neurological consequences. Thus, we present a review of two novel safe and effective approaches for treating AFTN; one surgical (transoral endoscopic thyroid surgery) and one non-surgical (radiofrequency ablation), as a means for expanding our treatment armamentarium.

Utility of Intraprocedural Contrast-Enhanced CT in Ablation of Renal Masses

OBJECTIVE. The purpose of this study was to evaluate the efficacy of radiofrequency ablation (RFA) of renal masses comparing a group who did not undergo intraprocedural CT and a group who did. MATERIALS AND METHODS. A retrospective review included 45 consecutively registered patients who underwent RFA of renal masses. If an adequate biopsy specimen was not obtained or follow-up was inadequate, the patient was eliminated from review from calculation of primary technical efficacy. The inclusion criterion was having undergone RFA with two cooled-tip electrodes. Baseline demographics (age, body mass index, and sex), renal mass characteristics (diameter, side, location, position, morphologic features, type of mass, and grade), technical details (repositioning and hydrodissection), and complications were evaluated. Follow-up images were evaluated to determine the presence of recurrence at the ablation site in the two groups. RESULTS. Among the 45 patients who underwent RFA, 13 did not undergo intraprocedural CT and 32 intraprocedural did. Thirty-five patients met the criteria for follow-up and positive biopsy results. For calculation of recurrence, 10 patients were in the group who did not and 25 were in group who did undergo intraprocedural contrast-enhanced CT. No correlation was found between baseline demographics, renal mass characteristics, and technical results of the two groups. There was an 89% overall technical efficacy rate with a 96% primary technical efficacy rate in the group who underwent intraprocedural CT compared with a 70% rate in the group who did not undergo intraprocedural CT. Negative correlation was found between the groups with respect to technical efficacy rate at p < 0.05. CONCLUSION. Intraprocedural contrast-enhanced CT yields important information about completeness of ablation during the procedure, allowing probe repositioning and thus better therapeutic effect.

Transarterial embolization of renal cell carcinoma as an adjunctive therapy prior to cryoablation: a propensity score matching analysis

PURPOSE

We aimed to assess the safety and effectiveness of transarterial embolization (TAE) prior to percutaneous cryoablation (PCA) in the management of renal cell carcinoma (RCC) compared with PCA alone using a propensity score matching analysis to minimize confounding factors.

METHODS

A retrospective review of all PCAs performed for renal masses identified 9 patients who underwent TAE prior to PCA. These patients were matched in a 2:1 ratio with patients who underwent PCA only using age, gender, and tumor size to create the propensity score model for matching. Other demographic, clinical, and outcomes data were collected.

RESULTS

The TAE+PCA group included 5 males and 4 females with a mean age of 67.9 years and mean tumor diameter of 51.7 mm. The PCA only group included 11 males and 7 females with a mean age of 66.8 years and mean tumor diameter of 46.2 mm. No significant differences in these propensity score matched characteristics were identified. Further, the groups had no significant differences in tumor geometry (P = 0.831), R.E.N.A.L. nephrometry scores (P = 0.144), or comorbidity indices (P = 0.392). TAE was technically successful and without complication in all cases. PCA was technically successful in 8 of 9 patients in the TAE+PCA group and in 14 of 18 patients in the PCA only group (P = 0.483). No significant differences in the rate of complications (P = 0.483), change in eGFR (P = 0.691), or change in hematocrit (P = 0.152) were identified between the two groups.

CONCLUSION

TAE of RCC prior to PCA is safe and technically feasible; however, no objective benefits over PCA alone were identified by propensity score matching analysis. Due to small sample size and limitations of the study, no definite conclusions should be drawn. Larger, prospective studies of this therapeutic approach are warranted.

Trans-Arterial Embolization of Renal Cell Carcinoma prior to Percutaneous Ablation: Technical Aspects, Institutional Experience, and Brief Review of the Literature

This report describes the technical aspects of trans-arterial embolization (TAE) of renal cell carcinoma prior to percutaneous ablation. All patients (n = 11) had a single renal mass (mean tumor diameter = 50.2 mm; range: 28-84 mm). Selective TAE was performed via the common femoral artery. Embolic materials included: particles alone (n = 4), coils alone (n = 1), particles + ethiodized oil (n = 2), particles + coils (n = 1), ethiodized oil + ethanol (n = 2), and particles + ethanol (n = 1). All embolizations were technically successful and no complications have been reported. After embolization, 10 patients underwent cryoablation while 1 patient underwent microwave ablation. Ablations were technically successful in 10 of the 11 patients. Only 3 minor complications were identified but none required treatment. No adverse effect on the patient's glomerular filtration rate was seen from the additional procedure (p = 0.84). TAE of renal cell carcinoma prior to percutaneous ablation is safe and technically-feasible.

Current status of renal biopsy for small renal masses

Small renal masses (SRMs) are defined as radiologically enhancing renal masses of less than 4 cm in maximal diameter. The incidence of renal cell carcinoma (RCC) has increased in recent years, which is mainly due to the rise in incidental detection of localized SRMs. However, the cancer-specific mortality rate is not increasing. This discrepancy may be dependent on the indolent nature of SRMs. About 20% of SRMs are benign, and smaller masses are likely to have pathologic characteristics of low Fuhrman grade and clear cell type. In addition, SRMs are increasingly detected in elderly patients who are likely to have comorbidities and are a high-risk group for active treatment like surgery. As the information about the nature of SRMs is improved and management options for SRMs are expanded, the current role of renal mass biopsy for SRMs is also expanding. Traditionally, renal mass biopsy has not been accepted as a standard diagnostic tool in the clinical scenario because of several issues about safety and accuracy. However, current series on SRM biopsy have reported high diagnostic accuracy with rare complications. Studies of modern SRM biopsy have reported diagnostic accuracy greater than 90% with very high specificity. Also, current series have shown very rare morbid cases caused by renal mass biopsy. Currently, renal biopsy of SRMs can be recommended in most cases except when patients have imaging or clinical characteristics indicative of pathology and in cases in which conservative management is not considered.

Radiofrequency ablation for treatment of benign thyroid nodules: systematic review

OBJECTIVE

To summarize the literature published to date on the use of radiofrequency ablation (RFA) in the treatment of benign thyroid nodules, to evaluate the effectiveness of this treatment, and to attempt an evaluation of factors that may influence treatment outcome.

STUDY DESIGN

Systematic review with meta-analysis.

METHODS

Systematic literature search was performed by two separate authors in four commonly used literature databases. Trials included in meta-analysis included only those presenting prospective data. Meta-analysis compared pretreatment values to post-treatment outcomes.

RESULTS

Of 46 full-text articles identified, nine articles satisfied inclusion criteria. Two of these articles were randomized controlled trials comparing RFA to placebo or to some other treatment. One article was a randomized controlled trial comparing one RFA treatment to two treatments. The remaining six articles were noncontrolled, prospective observational studies. All analyzed outcomes showed statistically significant improvements from baseline to final follow-up, including reduction in nodule size, improvement of symptom and cosmetic scores, and withdrawal from methimazole. Improvement in nodule size remained significant in both "hot" and "cold" nodule subgroups. Twelve adverse events were identified across all studies out of 306 total treatments. Two of these events qualified as significant adverse events. None of these events resulted in hospitalization or death.

CONCLUSIONS

Radiofrequency ablation is a safe and effective treatment for symptomatic thyroid nodules that are confirmed benign. However, the paucity of level 1 evidence comparing RFA to surgical or to other nonsurgical treatment modalities is concerning.

Maximizing parameters for tissue ablation by using an internally cooled electrode

PURPOSE

To compare an algorithm of gradually ramped-up power to a full-power-level technique to determine which technical parameters maximized tissue coagulation by using a saline-perfused electrode.

MATERIALS AND METHODS

Institutional review board approval was not necessary and animal committee approval was unnecessary because an ex vivo bovine liver model was used and the animals were not specifically killed for this study. This four-part experiment utilized multiple ablations of ex vivo bovine liver with a standard radiofrequency (RF) generator and an internally cooled needle. First, 10 RF ablations were performed at 20-60 W for 12 minutes. Second, ablation volumes obtained from an algorithm of eight ablations performed at 50 W were compared with those obtained from an algorithm of eight ablations that were gradually ramped-up to 50 W, until full impedance. Third, volumes obtained from 10 ablations performed at impedance control power levels were compared with those obtained from 10 ablations performed with a gradual ramp-up of power that started at 50 W, terminating at full impedance. Last, the third part was repeated, but with 11 ablations continuing past full impedance for 12 minutes each.

RESULTS

In the first part, maximum measurements of tissue coagulation seemed to plateau from 40 to 60 W. The second part produced significantly larger measurements of tissue coagulation than did the use of a constant power level of 50 W. The third and final parts produced larger measurements of tissue coagulation than did utilizing full power for 12 minutes. Larger measurements and volumes were obtained from repeat ablations after the generator reached impedance level than were obtained from ablations stopped at maximum impedance.

CONCLUSION

A gradual ramp-up of power and repeating ablations after power impedance level is reached are the two methods that increased tissue ablation in this ex vivo experiment.

Radiofrequency Ablation in Combination with Embolization in Metachronous Recurrent Renal Cancer in Solitary Kidney after Contralateral Tumor Nephrectomy

PURPOSE

To evaluate the feasibility and safety of minimally invasive, percutaneous techniques in metachronous recurrent renal cell cancers (RCCs) in solitary kidneys.

METHODS

In 4 patients, recurrent RCC was treated by radiofrequency ablation (RFA) (RITA, StarBurst) alone, and in 2 patients by RFA in combination with superselective transarterial particle-lipiodol embolization using 3 Fr microcatheters. RFA was guided by computed tomography in 5 patients, and by magnetic resonance imaging in 1 patient. Mean tumor diameter was 26.7 mm (range 10-45 mm). All interventions were technically successful; during follow-up 1 patient developed recurrent RCC, which was retreated by RFA after embolization.

RESULTS

No major peri- or postprocedural complications occurred. Changes in creatinine (pre- vs. post-intervention, 122 vs. 127 micromol/l) and calculated creatinine clearance (pre- vs. post-intervention, 78 vs. 73 ml/min) after ablation were minimal.

CONCLUSION

In single kidneys, percutaneous, minimally invasive techniques are safe and feasible. In large tumors, or where there are adjacent critical structures, we prefer a combination of embolization and thermal ablation (RFA).

RFA of renal cell carcinoma in a solitary kidney

The incidence of renal cell carcinoma (RCC) is increasing worldwide and diagnosis is made in an earlier stage due to increasing use of CT and ultrasound. Patients with a history of RCC have a high risk to develop another RCC within their remaining kidney. Especially, patients after tumor nephrectomy have to undergo follow-up examinations regularly allowing an early detection of new RCCs. Especially in patients with solitary kidney gold standard therapy (nephron-sparing surgery) can often account for consecutive renal failure with the need for hemodialysis. Percutaneous radiofrequency ablation (RFA) gained worldwide acceptance for the treatment of liver tumors in patients unable to undergo surgery. Furthermore, during the past few years, there is an increasing amount of publications dealing with the effectiveness of minimally invasive therapies like RFA in patients with renal masses. However, in the subgroup of patients with solitary kidney suffering from RCC, there are only case reports regarding safety and midterm outcome available so far. Therefore, the aim of this article is to briefly describe the basic technical principles of RFA and then focus on indications, technique, safety and the midterm outcome after treatment in terms of renal function and relapse.

Elastographic measurements of in-vivo radiofrequency ablation lesions of the kidney

BACKGROUND AND PURPOSE

Elastography may prove useful for monitoring radiofrequency ablative (RFA) therapy because heat-ablated tissues are more elastic than untreated tissues. Herein, we report our initial evaluations of the reliability of elastography for delineating thermal-lesion boundaries at the time of RFA of porcine kidneys.

MATERIALS AND METHODS

In-vivo RFA was performed on 20 kidneys from 10 40-kg female pigs. Elastography was performed at the time of surgery and after 48 hours. The imaging plane was perpendicular to the axis of the RF electrode so that the ablated region was around the center of the plane. Measurements of the sections representing the same image plane used for elastography were taken at pathologic examination and compared with the measurements obtained from the elastograms.

RESULTS

We found a statistically significant correlation between elastography and pathology measurements with respect to the area and volume estimates (r = 0.9302 and r = 0.953, respectively). Overall, elastography slightly underestimated the lesion size, as judged by the digitalized pathologic images, a finding consistent with previous reports.

CONCLUSION

We found a correlation between the area and volume estimates of thermal lesions that were based on elastographic images and the measurements from gross pathologic dimensions. A significant limitation of renal RFA is the inaccuracy of current imaging modalities to provide real-time monitoring, and elastography may prove to be reliable for delineating the resulting thermal lesions.

Image-guided radiofrequency ablation of renal cell carcinoma

The incidence of renal cell carcinoma is rising with the increased number of incidental detection of small tumours. During the past few years, percutaneous imaging-guided radiofrequency ablation has evolved as a minimally invasive treatment of small unresectable renal tumours offering reduced patient morbidity and overall health care costs. In radiofrequency ablation, thermal energy is deposited into a targeted tumour by means of a radiofrequency applicator. In recent studies, radiofrequency ablation was shown to be an effective and safe modality for local destruction of renal cell carcinoma. Radiofrequency applicator navigation can be performed via ultrasound, computed tomography or magnetic resonance guidance; however, ultrasound seems less favourable because of the absence of monitoring capabilities during ablation. On-line monitoring of treatment outcome can only be performed with magnetic resonance imaging giving the possibility of eventual applicator repositioning to ablate visible residual tumour tissue. Long-term follow-up is crucial to assess completeness of tumour ablation. New developments in ablation technology and radiological equipment will further increase the indication field for radiofrequency ablation of renal cell carcinoma. Altogether, radiofrequency ablation seems to be a promising new modality for the minimally invasive treatment of renal cell carcinoma, which was demonstrated to exhibit high short-term effectiveness.

Radiofrequency ablation combined with renal arterial embolization for the treatment of unresectable renal cell carcinoma larger than 3.5 cm: initial experience

The purpose of the study was to evaluate the feasibility, safety, and therapeutic effects of the combination of renal arterial embolization and radiofrequency (RF) ablation to reinforce the anticancer effect on renal cell carcinomas (RCCs) measuring 3.5 cm or larger. This study was undertaken to evaluate this combined therapy on large RCCs-based tumor geometry. Eleven patients with 12 RCCs 3.5 cm or larger in diameter (3.5-9.0 cm) underwent combined therapy. Two were exophytic tumors, and the remaining 10 tumors had components extending into the renal sinus fat. Tumor vessels were selectively embolized in nine patients and the renal artery was completely embolized in two patients with polyvinyl alcohol or ethanol mixed with iodized oil. RF ablation was percutaneously done under the computed tomographic (CT)-fluoroscopic guidance. Response to treatment was evaluated by dynamic contrast-enhanced CT and magnetic resonance (MR) imaging. Tumor enhancement was eliminated after a single RF session in nine tumors (75%), after two sessions in two tumors (17%), and after four sessions in one tumor (8%). Both exophytic tumors (100%) and 7 of 10 tumors having components in the renal sinus fat (70%) were completely ablated with a single RF session. All tumors remained controlled during a mean follow-up period of 13 months and showed significant reduction in tumor sizes (5.2 +/- 1.7 cm to 3.6 +/- 1.4 cm, p < 0.001). A delayed abscess developed in the ablated lesion in a patient, which was percutaneously drainaged. Combined therapy as described in this report is a feasible, relatively safe, and promising treatment method for large RCCs regardless of tumor geometry.

Renal tumors

The treatment of RCC is rapidly changing. The introduction of minimally invasive thermal ablation techniques offers a safe and accurate alternative to open surgery in the treatment of renal tumors. Because of its technical benefits, percutaneous radiofrequency ablation took the lead among these minimally invasive techniques. Supported by convincing results from experimental studies, patient data prove this procedure to be safe and efficient. As a minimally invasive and nephron-sparing technique, it is well suited for patients with a single kidney, multiple tumors, or contraindications for open surgery.

Use of an Arterial Tourniquet to Achieve Complete Radiofrequency Ablation of a Renal Metastasis

Radiofrequency (RF) coagulation of skeletal metastases is usually performed for pain relief. However, patients with solitary skeletal metastasis may benefit from more aggressive attempts to achieve local control. The authors report a case in which an arterial tourniquet was used to enhance the effectiveness of RF treatment of a calcaneal renal cell metastasis, leading to long-lasting local control with preservation of ambulation.

Efficacy of Transhepatic Radiofrequency Ablation of Renal Cell Carcinoma

OBJECTIVE

The purpose of this report is to describe an alternative, using a transhepatic route, to CT guidance of radiofrequency ablation of renal masses.

CONCLUSION

In four supine patients, radiofrequency ablation of a right renal mass was performed under sonographic guidance. The radiofrequency ablation needle was placed transhepatically into the mass. Color sonography was useful in guiding needle placement and avoiding intervening vessels in the liver and kidney. This technique may be used in selected patients as an alternative to CT guidance of radiofrequency ablation.

Nonoperable Recurrent Renal Cell Carcinoma: Management with Embolization and CT-Guided RF Ablation

We report the case of a 59-year-old male who underwent embolization and computed-tomography-guided radiofrequency ablation of a recurrent renal cell carcinoma that developed after radical nephrectomy in contiguity to the inferior vena cava. The alternative of a new operation was rejected because of the proximity of the tumor to the vessel and percutaneous approach seemed to be the better solution.

Radiofrequency ablation of renal cell carcinoma: part 1, Indications, results, and role in patient management over a 6-year period and ablation of 100 tumors

OBJECTIVE

The objectives of our article are to review our experience with radiofrequency ablation of renal cell carcinoma and to assess size and location as predictors of the ability to achieve complete necrosis by imaging criteria.

MATERIALS AND METHODS

Over a 6-year period, 100 renal tumors in 85 patients underwent radiofrequency ablation at a single institution. The absence of enhancement on CT or MRI after radiofrequency ablation was interpreted as complete coagulation necrosis. Results were analyzed by tumor size and location using multivariate analysis. A p value of 0.05 or less was considered significant.

RESULTS

All 52 small (3 cm) and all 68 exophytic tumors underwent complete necrosis regardless of size, although many large tumors (> 3 cm) required a second ablation session. Using multivariate analysis, we found that both small size (p < 0.0001) and noncentral location (p = 0.0049) proved to be independent predictors of complete necrosis after a single ablation session. Location was a significant predictor (p = 0.015) of complete necrosis after any number of sessions, whereas size showed a strong trend (p = 0.059) toward predicting success after any number of sessions. Complications were either self-limited or readily treated and included hemorrhage (major, n = 2; minor, n = 3), inflammatory track mass (n = 1), transient lumbar plexus pain (n = 2), ureteral injury (n = 2), and skin burns (n = 1).

CONCLUSION

Radiofrequency ablation is a promising minimally invasive therapy for renal cell carcinoma in patients who are not good operative candidates. Small size and noncentral location are favorable tumor characteristics, although large tumors can sometimes be successfully treated with multiple ablation sessions.

Percutaneous radiofrequency ablation of renal cell carcinoma

BACKGROUND

Preliminary data regarding the use of percutaneous radiofrequency ablation (RFA) for the treatment of renal cell carcinoma (RCC) are encouraging, and show the technique to be associated with minimal morbidity. Thus, the current study was designed to evaluate the clinical applications, treatment efficacy, and complications of percutaneous RFA in RCC.

METHODS

From February 2003 to February 2004, 12 consecutive patients with histopathologically proven RCC underwent imaging-guided percutaneous RFA. The mean age of the patients (8 men and 4 women) was 76 years (range, 56-87 years), and mean tumor diameter was 3.7 cm (range, 2.2-8.0 cm). The efficacy of RFA was evaluated with contrast-enhanced, dynamic computed tomography (CT) performed 1 month after treatment, and then every 3 months. A Radionics device with an internally cooled electrode was used in 7 patients, and a radiofrequency interstitial tissue ablation (RITA) device with an expandable needle electrode was used in 5. Complete necrosis was defined as a lack of contrast enhancement in the treated region on follow-up CT studies.

RESULTS

Overall, 16 sessions of RFA were performed for 12 solitary renal tumors in 12 patients: 8 patients underwent a single RFA session, whereas 4 had 2 sessions. Dynamic CT after RFA showed complete necrosis in 9 of 12 tumors. In 3 patients with tumors of 4.5-8.0 cm in diameter, enhancement of residual tissue was observed after RFA treatment, thus indicating residual tumor. Complete tumor necrosis was seen in all 5 tumors (100%) of diameter < or = 3.0 cm; 3 of 4 tumors (75%) of diameter 3.1-5.0 cm; and 1 of 3 tumors (33%) of diameter > 5.0 cm. A big subcapsular hematoma, which was found in 1 patient after RFA, resolved completely within 10 months without treatment; no serious complications occurred in the other 11 patients.

CONCLUSION

Percutaneous RFA is effective in the treatment of RCC. It is most successful for tumors not larger than 3 cm in diameter, and has a satisfactory success rate in tumors of 3-5 cm in diameter. The rate of serious complications of RFA is low. Further studies are necessary to determine the long-term efficacy of RFA in RCC.

Embolización arterial selectiva en un caso de carcinoma de células renales como alternativa terapéutica

We show a big renal cell carcinoma case in an aged woman with many pathology associated. In view of the family refuse to make the radical surgery and the high surgical risk we decided to apply transarterial embolization treatment with polivinil alcohol particles (PVA). 28 months later the patient becames with no symptoms and with high quality life. We come to the conclusion that embolization is an effective therapeutic for the symptoms control in selectionated cases.

Review of radiofrequency ablation for renal cell carcinoma

This review will discuss how minimally invasive, image-guided radiofrequency (RF) tumor ablation [i.e., coagulating tumor using short-duration heating (<15 minutes) by directly applying temperatures >50 degrees C via needle electrodes] is being incorporated as a clinical tool for the treatment of renal cell carcinoma. RF ablation has been used to treat focal liver tumors. Potential benefits of this thermal therapy include reduced morbidity and mortality compared with standard surgical resection and the ability to treat nonsurgical patients. More recently, this technique has been introduced to treat focal renal tumors, particularly incidental lesions smaller than 3 cm in elderly patients and those with comorbid conditions. Other uses have included treatment in patients with von Hippel-Lindau syndrome and other diseases that predispose patients to multiple renal carcinomas, where renal parenchymal preservation is desired. Techniques, complications, and results will be discussed. Additionally, strategies that we are currently studying to improve RF outcomes and enable the potential treatment of larger tumors will be addressed. Most notably, recent data on increased coagulation achieved by combining RF ablation with antivascular/antiangiogenic therapies, such as arsenic trioxide, that reduce blood flow and promote heat retention are provided.

Percutaneous US-guided RF thermal ablation for malignant renal tumors: preliminary results in 13 patients

Minimally invasive treatment for small renal cell carcinoma (RCC) can be necessary in selected patients and, anyway, is desirable. In situ ablation techniques, including RFA, have been developed. The aim of this study is to evaluate the feasibility, safety and short-term local effectiveness of percutaneous US-guided RFA in a small series, as well as mid-term patient outcome. Thirteen patients with a total of 18 tumors (17 small lesions, 35 mm in size or less, and a larger one, 75 mm in size) underwent 19 RFA sessions. Seven patients had a solitary kidney, and three suffered from VHL disease, too. We treated four lesions in a patient with a bilateral tumor. In another patient, three lesions were ablated. Seventeen tumors were RCC; one was a metastasis from lung cancer. Eight lesions were parenchymal, six exophytic, two parenchymal/exophytic, one parenchymal/central and one central. A monopolar RF system with multitined expandable electrode needles was used. The 35-mm lesion underwent two sessions; the 75-mm lesion was treated with transcatheter arterial embolization before RFA. Tumors with complete loss of contrast enhancement at short-term CT (or MR) were considered successfully treated. Percutaneous US-guided RFA was always feasible without major complications. The success rate after a single treatment in tumors less than 35 mm in size was 88.2% (15/17) and rose to 94.1% (16/17) after the second treatment of the largest lesion. After a mean 14-month follow-up, no successfully treated lesions recurred locally. Only the patient with metastasis from lung cancer died from disease progression in a further location, while all other patients are alive, with renal function still sufficient to avoid dialysis. US guidance allows an easy and safe percutaneous approach for RFA of small non-parahilar RCC. The treatment is locally effective and can be proposed as a minimally invasive therapy for patients with contraindications to surgery or to those expressing an informed consent. Based on the results of this study and of the literature, mid-term results on the clinical usefulness are very encouraging.

Effects of perfusion on radiofrequency ablation in swine kidneys

PURPOSE

To evaluate the effect of vascular occlusion on the size of radiofrequency (RF) ablation lesions and to evaluate embolization as an occlusion method.

MATERIALS AND METHODS

The kidneys of six swine were surgically exposed. Fifteen RF ablation lesions were created in nine kidneys by using a 2-cm-tip single-needle ablation probe in varying conditions: Seven lesions were created with normal blood flow and eight were created with blood flow obstructed by means of vascular clamping (n = 5) or renal artery embolization (n = 3). The temperature, applied voltage, current, and impedance were recorded during RF ablation. Tissue-cooling curves acquired for 2 minutes immediately after the ablation were compared by using regression analysis. Lesions were bisected, and their maximum diameters were measured and compared by using analysis of variance.

RESULTS

The mean diameter of ablation lesions created when blood flow was obstructed was 60% greater than that of lesions created when blood flow was normal (1.38 cm +/- 0.05 [standard error of mean] vs 0.86 cm +/- 0.07, P <.001). The two methods of flow obstruction yielded lesions of similar mean sizes: 1.40 cm +/- 0.06 with vascular clamping and 1.33 cm +/- 0.07 with embolization. The temperature at the probe tip when lesions were ablated with normal blood flow decreased more rapidly than did the temperature when lesions were ablated after flow obstruction (P <.001), but no significant differences in tissue-cooling curves between the two flow obstruction methods were observed.

CONCLUSION

Obstruction of renal blood flow before and during RF ablation resulted in larger thermal lesions with potentially less variation in size compared with the lesions created with normal nonobstructed blood flow. Selective arterial embolization of the kidney vessels may be a useful adjunct to RF ablation of kidney tumors.

Needle-based ablation of renal parenchyma using microwave, cryoablation, impedance- and temperature-based monopolar and bipolar radiofrequency, and liquid and gel chemoablation: laboratory studies and review of the literature

BACKGROUND AND PURPOSE

Small renal tumors are often serendipitously detected during the screening of patients for renal or other disease entities. Rather than perform a radical or partial nephrectomy for these diminutive lesions, several centers have begun to explore a variety of ablative energy sources that could be applied directly via a percutaneously placed needle-like probe. To evaluate the utility of such treatment for small renal tumors/masses, we compared the feasibility, regularity (consistency in size and shape), and reproducibility of necrosis produced in normal porcine kidneys by different modes of tissue ablation: microwaves, cold impedance-based and temperature-based radiofrequency (RF) energy (monopolar and bipolar), and chemical. Chemoablation was accomplished using ethanol gel, hypertonic saline gel, and acetic acid gel either alone or with simultaneous application of monopolar or bipolar RF energy.

MATERIALS AND METHODS

A total of 107 renal lesions were created laparoscopically in 33 domestic pigs. Microwave thermoablation (N=12) was done using a Targis T3 (Urologix) 10F antenna. Cryoablation (N=16) was done using a single 1.5-mm probe or three 17F microprobes (17F SeedNet system; Galil Medical) (N=10 single probe and N=6 three probes); a double freeze cycle with a passive thaw was employed under ultrasound guidance. Dry RF lesions were created using custom-made 18-gauge single-needle monopolar probe with two or three exposed metal tips (GelTx) (N=12) or a single-needle bipolar probe (N=6) at 50 W of 510 kHz RF energy for 5 minutes. In addition, a multitine RF probe (RITA Medical Systems) was used in one set of studies (N=6). Both impedance- and temperature-based RF were evaluated. Chemoablation was performed with 95% ethanol (4 mL), 24% hypertonic saline (4 mL), and 50% acetic acid (4 mL) as single injections. In addition, chemoablation was tested with monopolar and bipolar RF (wet RF). Tissues were harvested 1 week after ablation for light microscopy.

RESULTS

In 11 of the 15 ablation techniques, there was complete necrosis in all lesions; however, three ethanol gel lesions had skip areas, three hypertonic saline gel lesions showed no necrosis or injury, and one monopolar RF and one bipolar RF lesion showed skip areas. In contrast to impedance-based RF, heat-based RF (RITA) caused complete necrosis without skip areas. All cryolesions resulted in complete tissue necrosis, and cryotherapy was the only modality for which lesion size could be effectively monitored using ultrasound imaging.

CONCLUSIONS

Cryoablation and thermotherapy produce well-delineated, completely necrotic renal lesions. The single-probe monopolar and bipolar RF produce limited areas of tissue necrosis; however, both are enhanced by using hypertonic saline, acetic acid, or ethanol gel. Hypertonic saline gel with RF consistently provided the largest lesions. Ethanol and hypertonic saline gels tested alone failed to produce consistent cellular necrosis at 1 week. In contrast, RITA using the Starburst XL probe produced consistent necrosis, while impedance-based RF left skip areas of viable tissue. Renal cryotherapy under ultrasound surveillance produced hypoechoic lesions, which could be reasonably monitored, while all other modalities yielded hyperechoic lesions the margins of which could not be properly monitored with ultrasound imaging.

Radiofrequency ablation of renal cell carcinoma

Small renal cell carcinomas of less than 4 cm diameter have been detected increasingly in asymptomatic patients because of the widespread use of cross-sectional imaging. Radical or partial nephrectomy is generally considered the reference for the treatment of a solitary renal cell carcinoma. However, for those patients who are not candidates for surgery, minimally invasive procedures may be desirable. Although percutaneous radiofrequency ablation for the treatment of renal cell carcinoma is a recent innovation, the results of preliminary clinical series and animal studies are encouraging, and show it to be technically feasible with minimal morbidity. In this article, we review the technique, indications, imaging findings, as well as the results of clinical and animal studies of radiofrequency ablation for the treatment of renal cell carcinoma.

Interstitial photon radiation

Most minimally invasive ablative techniques utilize thermal energies for tissue destruction. However, the heat-sink phenomenon may limit the efficacy of radiofrequency ablation and cryotherapy of tissue near blood vessels. One alternative non-temperature-dependent ablative technique is photon radiation. This radiation is dependent on energy and intensity, and its effects are influenced only by the density of the surrounding tissue. Photon radiation therapy may offer a unique alternative for ablating tissue surrounding vascular structures.

Radiofrequency Interstitial Tumor Ablation: Dry Electrode

With the shift in the treatment of small renal tumors from radical extirpative surgery to nephron-sparing approaches, dry-electrode radiofrequency ablation (RFA) has emerged as one potential modality. This application of RF energy leads to the production of heat within the treatment zone secondary to the native impedance of living tissue. Animal studies and human clinical series have demonstrated that RFA can create controlled, targeted, reproducible, and lethal lesions. Most clinical series have reported promising results, although some authors question the totality of tumor destruction by RFA. With time, the efficacy of RFA, as measured by patient survival, will be determined. Once this is known, RFA may be compared with other therapeutic modalities for small renal tumors to determine its place.

Imaging-guided percutaneous radiofrequency ablation of solid renal masses: techniques and outcomes of 38 treatment sessions in 32 consecutive patients

OBJECTIVE

The purpose of this study was to describe the treatment techniques and results of 38 consecutive imaging-guided percutaneous radiofrequency ablations of solid renal masses performed in 32 patients.

MATERIALS AND METHODS

Solid renal masses in 32 patients underwent 38 treatment sessions using imaging-guided percutaneous radiofrequency ablation. During 36 sessions, radiofrequency ablation was performed using CT guidance, and two, using sonographic guidance. The average patient age was 76 years (range, 52-87 years), and the average renal mass size was 2.6 cm (range, 1-5 cm). The average number of radiofrequency treatments per solid mass at each session was 2.4 (range, 1-6 treatments), and the average time per treatment was 9.2 min (range, 3-14 min). A single electrode was used in 12 sessions, and a cluster electrode was used in 26 sessions. The average follow-up time was 9 months (range, 1-36 months).

RESULTS

Twenty-six of 32 patients had successful treatment of the solid renal mass using percutaneous imaging-guided radiofrequency ablation after one treatment session. Successful treatment was defined as lack of enhancement of the treated region on follow-up CT. Six of 32 patients had residual enhancing tissue after the first treatment session and returned for a second session. Five of these six retreatments were successful. Masses requiring a second treatment session were significantly larger than masses treated in a single session (3.5 vs 2.4 cm, respectively; p = 0.0013). Two patients had perinephric hematomas (which did not require transfusion), and one patient developed a 5-mm skin metastasis at the electrode insertion site, which was resected without recurrence.

CONCLUSION

Percutaneous imaging-guided radiofrequency ablation shows promise in the treatment of solid renal malignancies.

Radiofrequency ablation of renal transitional cell carcinoma with protective cold saline infusion

Radiofrequency (RF) ablation is a feasible option for treatment of renal tumors when definitive tumor resection is not performed. Renal hilar and ureteral masses are generally more difficult than peripheral renal tumors to approach with RF ablation because of the higher associated risks of injury to the hilar vessels and the collecting system. This report presents a case of RF ablation of transitional cell carcinoma of the ureteropelvic junction, performed successfully for intractable hematuria. Significant injury to the uroepithelium was avoided by the concomitant use of a cold saline infusion into the collecting system of the kidney.

Renal cell carcinoma: clinical experience and technical success with radio-frequency ablation of 42 tumors

PURPOSE

To evaluate clinical experience with percutaneous image-guided radio-frequency (RF) ablation of renal cell carcinoma (RCC) and to assess factors that may influence technical success.

MATERIALS AND METHODS

Thirty-four patients who underwent RF ablation of 42 RCC tumors during a 3.5-year period were evaluated. Overlapping ablations were performed on the basis of tumor size and geometry. Technical success was defined as elimination of areas that enhanced at imaging within the entire tumor. With the exception of those patients with renal insufficiency, who were followed up with unenhanced and gadolinium-enhanced magnetic resonance imaging, patients were followed up with unenhanced and contrast material-enhanced computed tomography. Univariate analysis of the results was performed with the Fisher exact test to assess the effect of tumor size and location on technical success. P <or=.05 was considered to represent a significant difference. Complications and the management and outcomes of the complications were recorded.

RESULTS

All 29 exophytic tumors (mean size, 3.2 cm; size range, 1.1-5.0 cm) were completely ablated, as were two parenchymal tumors. The remaining 11 tumors had a component in the renal sinus. For large (>3.0 cm) tumors, presence of a tumor component in the renal sinus was a significant negative predictor of technical success (P =.004); only five of these 11 tumors were completely treated, compared with 11 of 11 tumors without a renal sinus component. A similar analysis was not possible for small tumors because no small tumors involved the renal sinus. Four complications occurred in a total of 54 ablation sessions: one minor hemorrhage, two major hemorrhages, and one ureteral stricture.

CONCLUSION

RF ablation of RCC can be successful in exophytic RCC tumors up to 5.0 cm in size. Tumors larger than 3.0 cm with a component in the renal sinus are more difficult to treat but can be ablated successfully.

Radiofrequency ablation with and without balloon occlusion of the renal artery: an experimental study in porcine kidneys

PURPOSE

To compare thermal lesion volumes and associated renal damage (other than thermal lesions) when radiofrequency (RF) ablation is performed with and without balloon occlusion of the renal artery in normal porcine kidneys.

MATERIALS AND METHODS

RF ablation was performed in six pigs. An electrode with eight circumferential prongs arranged in a circle 20 mm in diameter was inserted into the lower pole of the kidney. In each animal, renal ablation was performed with balloon occlusion of the renal artery in one kidney and without balloon occlusion in the contralateral kidney. The volume of the thermal lesion and associated renal damage other than the thermal lesion were compared by angiography and histology between the groups of kidneys ablated with and without arterial occlusion. The volume of thermal lesion was measured by tracing the thermal lesions of sliced kidneys and multiplying each area by the slice thickness (5 mm).

RESULTS

Renal ablation with arterial occlusion consistently created nearly spherical thermal lesions with a mean volume of 5,399 mm(3) +/- 902. RF ablation without arterial occlusion, conversely, created irregular, mushroom-shaped thermal lesions limited to the region around the prongs and shaft of the electrode, with a mean volume of 2,759 mm(3) +/- 1,069 (P <.001). Renal arteriography showed occlusion of interlobar arteries penetrating the thermal lesions and perfusion defects peripheral to the thermal lesions immediately after RF ablation. Perfusion defects were larger in kidneys ablated with arterial occlusion than in those ablated without arterial occlusion (1,499 cm(2) +/- 354 vs 499 cm(2) +/- 352; P <.001).

CONCLUSIONS

Renal RF ablation with arterial occlusion consistently provides larger thermal lesions than ablation without arterial occlusion does, but it induces renal infarction peripheral to the thermal lesion.

Percutaneous radiofrequency ablation of renal tumors: technique, limitations, and morbidity

OBJECTIVES

To evaluate our evolving experience with percutaneous radiofrequency (RF) renal tumor ablation and focus on our technique to ensure maximal treatment efficacy and reduce the possibility of complications.

METHODS

Fifteen patients with small (less than 4 cm) posterior or lateral contrast-enhancing (more than 10 Hounsfield units) renal tumors were candidates for RF treatment. Of these patients, 12 (13 tumors) received computed tomography-guided percutaneous RF ablation. General anesthesia was administered in all but our first 2 patients, who received intravenous sedation. After treatment, patients were closely followed up with computed tomography scans at 6 weeks and 3, 6, and 12 months, and every 6 months thereafter. Successful ablation was defined as a lesion along with a margin of normal parenchyma that no longer enhanced (less than 10 Hounsfield units) on follow-up contrast imaging.

RESULTS

The mean tumor size was 2.4 +/- 0.6 cm. The average procedure time was 95 minutes (range 60 to 150) and length of stay 0.9 days. All patients underwent the procedure without any major complications. At a mean follow-up of 4.9 months, 12 (93%) of 13 tumors were successfully ablated. In 3 patients, the procedure was not performed because of intervening bowel or lung parenchyma when positioned in the prone position before the procedure. Computed tomography-guided percutaneous RF ablation of small renal tumors is a viable minimally invasive treatment option with a high short-term success rate and low morbidity. This new technology must be uniformly applied to assess its long-term efficacy.

Magnetic resonance imaging-guided laser thermal ablation of renal tumours

OBJECTIVE

To test the hypothesis that magnetic resonance imaging (MRI)-guided laser thermal ablation (LTA) of inoperable renal tumours is a safe, tolerable and potentially effective treatment.

PATIENTS AND METHODS

Nine patients (aged 56-81 years) with malignant renal tumours underwent percutaneous LTA under MRI guidance in a 0.5 T open magnet. Real-time colour thermal mapping was used to monitor tumour ablation, and the follow-up was with gadolinium-enhanced MRI at 6 weeks and (where appropriate) 3-4 months after the procedure. Tumour volume and percentage tumour enhancement before and after ablation were compared. The percentage of tumour ablated on real-time T1-weighted thermal maps was compared with that on gadolinium-enhanced follow-up MRI.

RESULTS

The mean (range) follow-up was 16.9 (3-32) months after the first ablation. The mean tumour size did not change significantly, but the mean percentage of viable tumour decreased significantly from 73.7% before to 29.5% after ablation (P = 0.012, Wilcoxon signed-ranks test). Thermal maps correlated moderately well with follow-up MRI in predicting the extent of tumour ablation (Pearson correlation coefficient 0.55). There were two minor and one major complication.

CONCLUSION

In this pilot study of patients unsuitable for surgery, MRI-guided LTA of renal tumours was safe, feasible (being well tolerated by the patient) and significantly reduced enhancing tumour volume by a mean of 45%.

Radio frequency ablation of renal cell carcinoma: preliminary clinical experience

PURPOSE

We assess the feasibility, safety and efficacy of radio frequency ablation of small peripheral renal cell carcinomas.

MATERIALS AND METHODS

Five patients with a histologically proven renal cell carcinoma 30 to 40 mm. in diameter were treated with radio frequency ablation. A triple needle electrode was percutaneously advanced into each tumor under sonographic (4 cases) or computerized tomography (CT) (1) guidance. The radio frequency generator was activated for 15 minutes in each location where the electrode had been placed. Patients were then followed with CT and blood tests every 2 months for 6 months and every 3 months thereafter.

RESULTS

Four tumors required 1 radio frequency delivery and 1 required 2 applications during the same session. No complications were encountered except for a subcapsular hematoma in 1 patient, which resolved spontaneously. Two patients experienced transient hematuria. Of the patients 4 were discharged from the hospital after 2 days and 1 after 1 day. After 6 to 18 months (median 9) all patients were tumor-free on CT without suppress additional treatment.

CONCLUSIONS

In this small preliminary study radio frequency ablation of small peripheral renal cell carcinomas appears to be a feasible, safe and promising technique.

Retroperitoneoscopic radiofrequency ablation of a solid renal mass

PURPOSE

To report a new technique for radiofrequency (RF) ablation of a solid renal mass.

PATIENT AND METHODS

An 83-year-old man with a history of chronic renal insufficiency was found to have solid mass in the right kidney. Retroperitoneoscopic localization of the renal mass was accomplished using intraoperative ultrasonography. The lesion was treated with a 14-gauge RITA Starburst XL probe (Rita Medical Systems, Inc., Mountain View, CA).

RESULTS

The total treatment time included two cycles of 5.5 minutes. There were no intraoperative complications. Tissue desiccation was noted during treatment. A CT scan 48 hours after ablation showed a decrease in the density of the lesion suggestive of coagulation necrosis. The postoperative hospital course was uneventful.

CONCLUSION

The retroperitoneal laparoscopic technique is a feasible approach to performing RF ablation of a solid renal mass. It facilitates direct insertion of the RF probe, allows viewing and avoidance of adjacent structures such as bowel, and permits better staging by enabling biopsy of perirenal fatty tissue.

Radiofrequency ablation for eradication of renal tumor in a rabbit model by using a cooled-tip electrode technique

BACKGROUND

Radiofrequency ablation (RFA) has emerged as a potential alternative for surgery in clinical oncology. This animal experiment was conducted to evaluate the feasibility of RFA in the treatment of renal tumor.

METHODS

Eighteen rabbits with renal implantation of VX2 tumors were divided into two groups. Group A (n = 12) was treated with RFA by using a cooled-tip RF system at 30 W for 80 to 180 seconds. Group B (n = 6) received a sham operation. The therapeutic efficacy was evaluated by survival rate, magnetic resonance imaging (MRI), and histology.

RESULTS

All animals in group B died within 3 months after tumor implantation. Total tumor eradication was achieved in 10 of 12 rabbits (83.3%) in group A, of which 5 rabbits survived longer than 6 months (absolute eradication) and another 5 rabbits were found free of viable tumor when killed (relative eradication). Two rabbits experienced local tumor relapse, lung metastasis, or both. Six-month survival rate of RFA-treated rabbits was significantly higher (P < .01) than that of control rabbits. The typical MRI appearances of the acute RFA lesion consisted of five characteristic concentric zones, which corresponded to central needle track (zone A), tumor coagulation (zone B), renal tissue coagulation (zone C), peripheral hemorrhage (zone D), and inflammatory layer (zone E) on histology.

CONCLUSIONS

RFA may become a promising therapy for the treatment of renal tumor. MRI is a useful modality for assessment of renal tumor ablation.