General Anesthesia and Contrast-Enhanced Computed Tomography to Optimize Renal Percutaneous Radiofrequency Ablation: Multi-Institutional Intermediate-Term Results

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.

Radiofrequency Ablation of Small Renal Masses

Although the incidence of localized renal cell carcinoma has increased in recent decades due to greater use of imaging, the treatment has shifted to less invasive, nephron-sparing approaches. Radiofrequency ablation (RFA) is one accepted treatment modality for patients with small renal masses, and it has the advantage of being minimally invasive and highly nephron sparing, with the additional benefits of reduced blood loss and complication rates. We describe our experience with RFA with an accompanying instructional video outlining the procedure's key components.

Safety and oncologic efficacy of percutaneous MRI-guided cryoablation of intraparenchymal renal cancers

PURPOSE

The purpose of this study was to evaluate the safety and oncologic efficacy of percutaneous magnetic resonance imaging (MRI)-guided cryoablation of intraparenchymal renal cancer.

MATERIALS AND METHODS

Between February 2009 and August 2019, 31 consecutives patients with 31 entirely intraparenchymal biopsy-proven renal cancers were treated with cryoablation under MRI-guidance in our institution, and were retrospectively included. There were 20 men and 11 women with a mean age of 68.5±12.5 (SD) (range: 40-91years). Patient, tumor- and procedure-related, and follow-up data were retrospectively collected and analyzed. Local recurrence free (LRFS), metastasis free (MFS), disease free (DFS), cancer specific (CSS), and overall survivals (OS) were calculated.

RESULTS

Primary and secondary technical efficacy rates were 94% and 100%, respectively. Median follow-up was 27months. Seven (7/31; 23%) minor complications were noted in 7 patients. Patients showed a significant decline of the estimated glomerular filtration rate (eGFR) between baseline and nadir (mean basal eGFR 65.9±22.4 [SD] mL/min/1.73m²vs. mean nadir eGFR 52.8±26.0 [SD] mL/min/1.73m²; P<0.001), but only two showed a clinically significant renal function decline. Three-year estimates of primary and secondary LRFS, MFS, and DFS were 64% (95% confidence interval [CI]: 47-87%), 89% (95% CI: 78-99%), 83% (95% CI: 77-98%), and 45% (95% CI: 28-73%), respectively. No patients died due to renal cancer evolution (three-year CSS of 100%; 95% CI: 100-100%). One patient died 52months after the percutaneous treatment due to cryoablation-unrelated causes (three-year OS of 100%; 95% CI: 100-100%).

CONCLUSION

MRI-guided percutaneous cryoablation for intraparenchymal renal cancer offers good oncologic outcomes with acceptable complication rates and renal function worsening.

Comparison of Safety and Efficacy of Percutaneous Microwave Ablation of Central Versus Peripheral Renal Cell Carcinoma

PURPOSE

Thermal ablation of central renal cell carcinoma has been associated with increased risk of incomplete tumor necrosis and adverse events due to the proximity of tumors to the central collecting system and hilar vessels. The purpose of this study was to compare the safety and efficacy of computed tomography-guided percutaneous microwave ablation of central versus peripheral renal cell carcinoma.

MATERIALS AND METHODS

An institutional database was used to retrospectively identify 114 patients with renal cell carcinoma who were treated with computed tomography-guided percutaneous microwave ablation between January 2015 and December 2019. Patients were divided into two cohorts based on tumor location: central versus peripheral. Central renal tumors were defined as being within 4 mm of renal pelvis and/or ureter and peripheral tumors were defined as tumors beyond 4 mm the renal pelvis and/or ureter. Patient demographics, tumor type, technical success, primary technique efficacy and adverse events were recorded from the medical record. Technical success, primary technique efficacy and adverse events were compared between the two cohorts.

RESULTS

There were 44 patients in the central group and 70 patients in the peripheral group. Technical success was 100% for both groups. There was no significant difference in primary technique efficacy rates for peripheral compared to central tumors (93% vs. 89%, p = 0.49). There was no significant difference in overall adverse event rate (17.7% vs. 11.7%, p = 0.34) or Grade II or higher adverse event rate (7.8% vs. 2.6%, p = 0.17) following microwave ablation of central versus peripheral lesions. Adjunctive maneuvers of hydrodissection and/or pyeloperfusion were performed significantly more frequently for treatment for central tumors compared to peripheral tumors (53% vs. 29%, p = 0.006).

CONCLUSION

When adjunctive procedures were utilized more frequently for central compared to peripheral tumors, there was no significant difference in primary technique efficacy or adverse event rate following CT-guided percutaneous microwave ablation of central compared to peripheral renal cell carcinoma. The data suggest that MWA can be successfully applied to select central renal masses and adjunctive maneuvers such as pyeloperfusion should be strongly considered for patient safety.

LEVEL OF EVIDENCE III

Non-randomized controlled cohort study/follow-up study.

Computed tomography-guided biopsy for small renal masses before or immediately after tumor ablation: factors affecting diagnostic yield

PURPOSE

To evaluate the diagnostic yield of percutaneous renal mass biopsy (RMB) before and after ablation.

MATERIALS AND METHODS

In total, 333 renal masses in 332 consecutive patients underwent computed tomography (CT)-guided biopsies and were included in this study. All biopsies were performed with 18-gauge core needles with CT fluoroscopic guidance before ablation (n  =  234) or immediately after radiofrequency ablation (RFA) (n  =  40) or cryoablation (CA) (n  =  59). The safety and diagnostic yield of RMB were evaluated. Both univariate and multivariate analyses were used to identify factors affecting diagnostic yield.

RESULTS

No major complication occurred. The 281 specimens (84%) were diagnostic. There were 257 renal cell carcinomas (77%), 21 benign masses (6%), and 3 metastases (1%). The remaining 52 specimens (16%) were nondiagnostic. The diagnostic yields before ablation, after RFA, and CA were 91% (212/234), 80% (32/40), and 63% (37/59), respectively. Small masses (P  =  0.050 and 0.006), cystic masses (P < 0.001 and < 0.001), and post-CA (P < 0.001 and < 0.001) were independent and significant factors affecting the nondiagnostic results in both univariate and multivariate analyses.

CONCLUSION

CT-guided RMB can be nondiagnostic when the tumor is small, cystic, or biopsied immediately after CA.

Percutaneous Renal Ablation

Incidental small renal cell cancers are increasingly being diagnosed on cross-sectional imaging. This review article describes the indications for percutaneous ablation of small renal cell cancers, choice of ablation technologies and imaging follow-up.

Ablation of Small Renal Masses

Renal cell carcinoma is most commonly diagnosed in the sixth or seventh decade of life. Historically, surgical extirpation was the gold standard treatment option for small renal masses. However, given the comorbidities in this elderly population, not all patients are candidates for surgery. The development of minimally invasive ablative therapies has solved the surgical dilemma in this patient population. Furthermore, the 2017 American Urological Association guidelines recommends consideration of percutaneous image guided thermal ablation as a treatment option for masses smaller than 3 cm even in healthy individuals. Percutaneous image guided thermal ablation is an attractive treatment option providing excellent local tumor control, fewer complications, better preservation of the renal functions, faster recovery and shorter hospital stay. Various ablative modalities are available in clinical practice. This includes radiofrequency ablation, cryoablation, microwave ablation, irreversible electroporation, high intensity focused ultrasound, and laser ablation. In this review, we focus on the most commonly used modalities including radiofrequency ablation and cryoablation and to a lesser extent microwave ablation and irreversible electroporation.

Imaging of Small Renal Masses before and after Thermal Ablation

Thermal ablation of small renal masses is increasingly accepted as an alternative to partial nephrectomy, particularly in patients with multiple comorbidities. Many professional societies support this alternate treatment with updated guidelines. Before performing thermal ablation, it is important to stratify risk and assess technical feasibility by evaluating tumor imaging features such as size, location, and centrality. Routine postablation imaging with CT or MRI is necessary for assessment of residual or recurrent tumor, evidence of complications, or new renal masses outside the ablation zone. The normal spectrum and evolution of findings at CT and MRI include a halo appearance of the ablation zone, ablation zone contraction, and ablation zone calcifications. Tumor recurrence frequently manifests at CT or MRI as new nodular enhancement at the periphery of an expanding ablation zone, although it is normal for the ablation zone to enlarge within the first few months. Recognizing early tumor recurrence is important, as small renal masses are often easily treated with repeat ablations. Potential complications of thermal ablation include vascular injury, urine leak, ureteral stricture, nerve injury, and bowel perforation. The risk of these complications may be related to tumor size and location.^©RSNA, 2019.

Cone-Beam CT-Assisted Ablation of Renal Tumors: Preliminary Results

INTRODUCTION

Renal ablation is a recognized treatment modality for small renal masses. Cone-beam CT (CBCT) has been recently used in interventional oncology as a promising new guidance device, but this technology still needs to be validated for renal ablations. We aimed to assess the technical success of CBCT applications in renal ablative treatments.

MATERIALS AND METHODS

Between March 2016 and June 2018, 14 patients (mean age 69, range 54-83, 7F, 7M) underwent 21 renal ablations for histologically proven renal cell carcinoma (RCC). All treatments were performed with ultrasound (US) and CBCT guidance under general anesthesia in a dedicated angiography room setting. CBCT was mainly used to assess needle placement and to exclude complications at the end of the procedure. In two small lesions (< 1 cm), pre-acquired CBCT was co-registered with real-time US to obtain a US-CBCT fusion image guidance for tumor ablation.

RESULTS

Whether used alone or in combination with other imaging modalities, CBCT was proven to be technically successful in all 21 procedures to guide or assist tumor ablation. A primary technical efficacy of thermal ablation was achieved in 19/21 ablations (90.1%) at 1 month. Mean procedure duration was 100.2 min (range 160-64). Mean length of hospital stay was 2 days (range 1-10 days). All patients are still under active surveillance for a mean follow-up of 14.5 months (range 4-26 months).

CONCLUSIONS

CBCT for renal ablation guidance is a viable tool. Larger series are needed to compare it to MDCT.

An Anesthesiologist's View of Tumor Ablation in the Radiology Suite

The advent of radiology image-guided tumor ablation procedures has opened up a new era in minimally invasive procedures. Using CT, MRI, ultrasound, and other modalities, radiologists and surgeons can now ablate a tumor through percutaneous entry sites. What traditionally was done in an operating room via large open incisions, with multiple days in the hospital recovering, is now becoming an outpatient procedure via these new techniques. Anesthesiologists play a critical role in optimizing outcome in these patients. Knowledge by anesthesiologists of procedural goals, technology used, and inherit safety concerns of anesthetizing patients in the radiology suite are all critical to patients and proceduralists.

[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.

Decision Making: Thermal Ablation Options for Small Renal Masses

Renal cell carcinoma is a relatively common tumor, with an estimated 63,000 new cases being diagnosed in the United States in 2016. Surgery, be it with partial or total nephrectomy, is considered the mainstay of treatment for many patients. However, those patients with small renal masses, typically less than 3 to 4 cm in size who are deemed unsuitable for surgery, may be suitable for percutaneous thermal ablation. We review the various treatment modalities, including radiofrequency ablation, microwave ablation, and cryoablation; discuss the advantages and disadvantages of each method; and review the latest data concerning the performance of the various ablative modalities compared with each other, and compared with surgery.

Thermal ablative therapies for treatment of localised renal cell carcinoma: a systematic review of the literature

BACKGROUND AND AIMS

Small renal masses are commonly diagnosed incidentally. The majority are malignant and require intervention. The gold standard treatment is partial nephrectomy unless the patient has significant co-morbidities when surveillance or ablative therapies are utilised. The latter are relatively novel and their long-term efficacy and safety remain generally poorly understood. We performed a literature review to establish the current evidence on the oncological outcome of thermal ablative techniques in small renal masses treatment.

METHODS AND RESULTS

A systematic literature search was performed using PubMed, supplemented with additional references. Articles were reviewed for data on indications, tumour characteristics, ablative techniques, oncological outcome, impact on renal function and complications. The vast majority of articles identified were observational studies. There has not been any direct comparison against partial nephrectomy. Radiofrequency ablation and cryoablation are the techniques that are more commonly used. They have favourable oncological results on intermediate follow-up and indications that successful outcome is sustained long term. The morbidity and impact on renal function appear to be minimal.

CONCLUSION

Thermal ablative therapies are valid alternatives to partial nephrectomy for the treatment of small renal masses in patients unfit for surgery. Prospective long-term data will be needed before the indications for their use expand further.

Renal Ablation Techniques: State of the Art

OBJECTIVE

The purpose of this article is to describe the indications for and approach to image-guided percutaneous ablation of renal tumors.

CONCLUSION

Image-guided ablation techniques have become accepted treatment of patients with small renal tumors, a viable alternative to partial nephrectomy.

Renal ablation update

Thermal ablative technologies have evolved considerably in the recent past and are now an important component of current clinical guidelines for the treatment of small renal masses. Both radiofrequency ablation and cryoablation have intermediate-term oncologic control that rivals surgical options, with favorable complication profiles. Studies comparing cryoablation and radiofrequency ablation show no significant difference in oncologic control or complication profile between the two modalities. Early data from small series with microwave ablation have shown similar promising results. Newer technologies including irreversible electroporation and high-intensity-focused ultrasound have theoretical advantages, but will require further research before becoming a routine part of the ablation armamentarium. The purpose of this review article is to discuss the current ablative technologies available, briefly review their mechanisms of action, discuss technical aspects of each, and provide current data supporting their use.

Percutaneous radiofrequency ablation of renal tumors: a single-center experience

Purpose

To evaluate the oncological outcomes, complications, and changes in renal function in patients treated with computed tomography-guided percutaneous radiofrequency ablation (RFA) for small renal tumors.

Materials and Methods

The charts of patients who underwent RFA from 2006 to 2011 at a single institution were reviewed. Oncological and functional outcomes were assessed. Statistical analyses were performed with IBM SPSS ver. 18.0 (IBM Co., Armonk, NY, USA).

Results

A total of 44 RFAs were done in 40 patients. Biopsy prior to RFA was performed in 79.6% of procedures. Of those, 68.6% had renal cell carcinoma (RCC). Mean tumor diameter was 26.2 mm. Grade I complications occurred in 25% of cases (n=11, pain or elevated temperature) and grade II complications in 2.3% (n=1, perirenal bleeding needing two units of blood transfusion). Serum creatinine slightly increased by 0.14 mg/dL at 2 years after RFA (p<0.004). Tumor recurrences were suspected in 8 of 43 cases during follow-up. In five patients, the suspected recurrence was a false-positive as shown by a negative biopsy result or lack of contrast enhancement on subsequent imaging. The verified recurrence rate was 7.7% in all tumors and 2.5% in RCC at a mean follow-up of 2 years. Tumor-free survival was 90% in all patients and 87.5% in those with RCC. Metastasis-free survival was 97.5% and cancer-specific survival was 100%.

Conclusions

Percutaneous computed tomography-guided RFA shows promising results at intermediate follow-up. Suspected tumor recurrences are frequently false-positives findings. A longer follow-up is required to verify the durability of these results.

Cancer concepts and principles: primer for the interventional oncologist-part II

This is the second of a two-part overview of the fundamentals of oncology for interventional radiologists. The first part focused on clinical trials, basic statistics, assessment of response, and overall concepts in oncology. This second part aims to review the methods of tumor characterization; principles of the oncology specialties, including medical, surgical, radiation, and interventional oncology; and current treatment paradigms for the most common cancers encountered in interventional oncology, along with the levels of evidence that guide these treatments.

Improved outcome of percutaneous radiofrequency ablation in renal cell carcinoma: a retrospective study of intraoperative contrast-enhanced ultrasonography in 73 patients

OBJECTIVES

To evaluate the impact of contrast-enhanced ultrasonography (CEUS) during percutaneous radiofrequency ablation (PRFA) procedure in renal cell carcinoma (RCC).

METHODS

From January 2008 to July 2010, 73 patients with sporadic unilateral RCC were enrolled to our study (57 men and 16 women, age range: 37-78 years, mean age 57.9 years). The diameter of the tumor was 1.7-5.8, 3.4 cm on average. The patients were divided into two groups depending on the intraoperative ultrasonography type: CEUS group and conventional ultrasound group. Patients in CEUS group received CEUS before insertion of the electrode, and the second CEUS was performed right after the initial ablation to dynamically evaluate the images. If there was highly suspicious residue, additional ablation and repeated CEUS were applied. Patients in the conventional ultrasound group received PRFA guided by gray-scale ultrasound. All of these patients received contrast-enhanced computed tomography (CT) examination 7 days after the procedure (patients in CEUS group received CEUS conducted with each CT scan), with subsequent CT and CEUS assessment at 3, 6, and every 6 months thereafter.

RESULTS

The mean follow-up period was 22 months (range: 12-42 months). All tumors were biopsied before RFA. The local tumor control rate was 94.6% (35/37) in the CEUS group and 86.1% (31/36) in the conventional ultrasound group (P < 0.05); the cancer-specific survival rate and the overall survival rate were 100%. The post-RFA (12 months) mean GFR levels were 84.7 ± 27.5 mL/min/1.73 m(2) (P > 0.05, compared with pre-GFR: 86.4 ± 26.2 mL/min/1.73 m(2)) in the CEUS group and 81.9 ± 22.8 mL/min/1.73 m(2) (P > 0.05, compared with pre-GFR: 83.5 ± 23.7 mL/min/1.73 m(2)) in the conventional ultrasound group.

CONCLUSION

Intraoperative CEUS can "real-time" monitor the ablated area during PRFA procedure. This technique can help to achieve a higher success rate compared with conventional ultrasound. No impact of intraoperative CEUS has been found on GFR level.

Evidence-based clinical practice guideline for renal cell carcinoma: the Japanese Urological Association 2011 update

Remarkable advances have been made in medical practice in relation to renal cell carcinoma in recent years, and a large amount of new evidence has been accumulated. In keeping with the plan at the time the first version of the "Evidence-Based Clinical Practice Guideline for Renal Cell Carcinoma" compiled by the Japanese Urological Association was published in 2007, the Japanese Urological Association has just published a revised 2011 version. The main revisions regard the selection of treatment methods according to prognostic factors, reconsideration of treatment methods for small-diameter renal cell carcinoma and selection criteria for medical treatment of advanced renal cell carcinoma, including selection of neoadjuvant treatment with molecular targeted medicines. This Guideline presents clinical practice methods that are thought to be the most standard methods in Japan at the present time. In this English translation of a shortened version of the original Guideline, we cited particularly important clinical questions and references.

Zero ischemia laparoscopic radio frequency ablation assisted enucleation of renal cell carcinoma: experience with 42 patients

PURPOSE

We evaluated the safety and efficacy of zero ischemia, radio frequency ablation assisted tumor enucleation for renal cell carcinoma. We report the incidence of complications, positive surgical margins, local recurrence, and progression-free and disease specific survival rates.

MATERIALS AND METHODS

We retrospectively reviewed data on 42 patients with renal cell carcinoma treated with zero ischemia laparoscopic radio frequency ablation assisted tumor enucleation between March 2006 and November 2009. Median age was 60 years (range 37 to 82) and 31 patients (73.8%) were male. The median greatest tumor dimension was 3.4 cm (range 1.8 to 6.1). The Mann-Whitney U, chi-square and Fisher exact tests were used to compare bleeding and complications. The paired t and Mann-Whitney U tests were used to compare glomerular filtration rates. The Kaplan-Meier method was used to calculate survival.

RESULTS

We found 32 tumors with a greatest dimension of 4 cm or less and 10 with a greatest dimension of 4 to 7 cm. Median blood loss was 82.5 ml (range 15 to 210). Overall 7 complications (16.6%) occurred, including postoperative fever in 4 cases (Clavien grade II) and prolonged urinary leakage in 3 (Clavien grade III). The PADUA (preoperative aspects and dimensions used for an anatomical) score was associated with prolonged urinary leakage (p = 0.03) but not with overall complications. No patient had positive surgical margins. The glomerular filtration rate did not differ before vs 12 months after surgery. Three-year cancer specific, cumulative and progression-free survival was 100%, 97.3% and 96.4%, respectively.

CONCLUSIONS

Zero ischemia, laparoscopic radio frequency ablation assisted tumor enucleation of renal cell carcinoma is a safe, effective nephron sparing treatment that provides excellent oncological and functional outcomes.

Comparison of safety, renal function outcomes and efficacy of laparoscopic and percutaneous radio frequency ablation of renal masses

PURPOSE

With the increased incidence of low stage renal cancers, thermal ablation technology has emerged as a viable treatment option. Current AUA (American Urological Association) guidelines include thermal ablation as a treatment modality for select individuals. We compared the laparoscopic and percutaneous approach for the radio frequency ablation of renal tumors under the guidance of urological surgeons.

MATERIALS AND METHODS

We reviewed our radio frequency ablation database of patients with renal masses undergoing laparoscopic or computerized tomography guided percutaneous radio frequency ablation with simultaneous peripheral fiberoptic thermometry from November 2001 to January 2011 at a single tertiary care center. Data were collected on patient demographics, and surgical and clinicopathological outcomes stratified by approach.

RESULTS

A total of 298 patients with 316 renal tumors underwent laparoscopic (122 tumors) or computerized tomography guided (194 tumors) radio frequency ablation. There were no statistically significant differences between the laparoscopic and computerized tomography guided radio frequency ablation groups with respect to patient demographics, complication rates and renal functional outcomes (p>0.05). The 3-year Kaplan-Meier estimation of radiographic recurrence-free probability was 95% for computerized tomography guided radio frequency ablation and 94% for laparoscopic radio frequency ablation (p=0.84). Subanalysis of the 212 (67%) renal cell carcinoma tumors showed a 3-year Kaplan-Meier estimation of oncologic recurrence-free probability (post-ablation biopsy proven viable tumor) of 94% for computerized tomography guided radio frequency ablation and 100% for laparoscopic radio frequency ablation (p=0.16). Median followup was 21 months for laparoscopic radio frequency ablation) and 19 months for computerized tomography guided radio frequency ablation.

CONCLUSIONS

Laparoscopic and computerized tomography guided radio frequency ablation appear safe and effective with statistically equivalent rates of complications and recurrence.

Does renal mass ablation provide adequate long-term oncologic control?

Renal ablation (RA) is no longer used exclusively in patients with limited life expectancy. There are few studies reporting a minimum follow-up of 5 years. Biases and discrepancies within the literature are abundant. The outcomes of any series must be interpreted in the context of median follow-up time, reported tumor characteristics, ablation technique and training background of the practitioner, and the definition of tumor recurrence. The long-term oncologic efficacy of radiofrequency ablation (RFA) and cryoablation appear similar, although the percutaneous RFA technique may necessitate reablation in more cases. RA is associated with slightly higher rates of local recurrence compared to surgical excision.

Ablative therapies for renal tumors

Owing to an increased use of diagnostic imaging for evaluating patients with other abdominal conditions, incidentally discovered kidney masses now account for a majority of renal tumors. Renal ablative therapy is assuming a more important role in patients with borderline renal impairment. Renal ablation uses heat or cold to bring about cell death. Radiofrequency ablation and cryoablation are two such procedures, and 5-year results are now emerging from both modalities. Renal biopsy at the time of ablation is extremely important in order to establish tissue diagnosis. Real-time temperature monitoring at the time of radiofrequency ablation is very useful to ensure adequacy of ablation.

Complications following 573 percutaneous renal radiofrequency and cryoablation procedures

PURPOSE

To review complications related to percutaneous renal tumor ablation.

MATERIALS AND METHODS

Prospectively collected data related to renal radiofrequency (RF) ablation and cryoablation procedures performed from May 2000 through November 2010 were reviewed. This included 573 renal ablation procedures performed in 533 patients to treat 633 tumors. A total of 254 RF ablation and 311 cryoablation procedures were performed; eight patients underwent simultaneous RF ablation and cryoablation. The mean age of patients at the time of the procedure was 70 years (range, 24-93 y), and 382 of 573 procedures (67%) were performed in male patients. Complications were recorded according to the Clavien-Dindo classification scheme. Duration of hospitalization was also documented.

RESULTS

Of the 573 procedures, 63 produced complications (11.0% overall complication rate). There were 66 reported complications, of which 38 (6.6% of total procedures) were Clavien-Dindo grade II-IV major complications; there were no deaths. Major complication rates did not differ statistically (P = .15) between cryoablation (7.7%; 24 of 311) and RF ablation (4.7%; 12 of 254). Of the complications related to cryoablation, bleeding and hematuria were most common. Bleeding during cryoablation was associated with advanced age, increased tumor size, increased number of cryoprobes, and central position (P < .05). Of those treated with RF ablation, nerve and urothelial injury were most common. Mean hospitalization duration was 1 day for RF ablation and cryoablation.

CONCLUSIONS

Complications related to percutaneous renal ablation are infrequent. Recognition of potential complications and associated risk factors can allow optimization of periprocedural care.

Current status of ablative techniques for small renal masses

The past few decades have witnessed a steady increase in the number of newly diagnosed small renal masses. Although historically managed by surgical resection, many of these small renal masses are now noted to be amenable to less invasive treatment modalities including thermal ablation or active surveillance. Contemporary series suggest that renal thermal ablation (including cryoablation or radiofrequency ablation), when selectively employed, can maintain oncologic efficacy comparable to extirpation while minimizing complications and treatment morbidity. Therefore, as the incidence of small renal masses in elderly comorbid patients rises, it is likely we will see ablative techniques assume a greater role in management.

Current and future technology for minimally invasive ablation of renal cell carcinoma

Purpose of Review:

To provide an overview of the technologic advancements in the field of ablative therapy, focusing on the treatment of renal neoplasms.

Materials and Methods:

A MEDLINE search was performed using each specific ablative technique name as the search term. Articles written in the English language were selected for review. In cases of multiple reports by a single institution, the most recent report was utilized. Pertinent articles specific to the technologic advancement in ablative therapy were selected for review.

Recent Findings:

Intermediate-term oncologic outcomes of radiofrequency ablation (RFA) and cryoablation (CA) for the treatment of small renal masses are encouraging. For thermal therapies, molecular adjuvants to enhance cellular kill and local control have been developed. Improvements in microwave technology have allowed for reductions in antenna size and increases in ablation size. Laparoscopic high-intensity focused ultrasound (HIFU) probes have been developed to overcome the limitations of transcutaneous energy delivery, but HIFU remains experimental for the treatment of renal lesions. Irreversible electroporation (IRE), a novel nonthermal ablative technique, is currently undergoing clinical investigation in human subjects. Histotripsy causes mechanical destruction of targeted tissue and shows promise in treating renal and prostate pathology.

Summary:

Ablative techniques are commonly utilized in the primary treatment of urologic malignancies. The purpose of this review is to discuss technologic advances in ablative therapies with emphasis on the treatment of renal masses. RFA and CA show acceptable intermediate-term efficacy and technical refinement continues. Emerging technologies, including microwave thermotherapy, IRE, HIFU and histotripsy, are described with emphasis on the mechanism of cellular kill, energy delivery, and stage in clinical development.

Percutaneous cryoablation of renal masses >or=3 cm: efficacy and safety in treatment of 108 patients

PURPOSE

To evaluate our single institution experience with percutaneous cryoablation of renal masses >or=3 cm in diameter for complications and short-term outcomes.

PATIENTS AND METHODS

Between March 2003 and February 2009, 108 patients with 110 renal masses >or=3 cm in diameter were treated with percutaneous cryoablation therapy. Technical success of the ablation procedure, complications, and evidence for local tumor recurrence were evaluated for each patient.

RESULTS

Average maximal renal tumor diameter was 4.1 cm (range 3.0-8.3 cm; standard deviation 1.1 cm). A single cryoablation procedure was performed for treatment of each patient. A technically successful ablation was achieved for 107 of 110 (97%) tumors. The three technical failures all resulted from incomplete cryoablation of the deepest margin of a centrally located renal tumor. A total of 9 severe adverse events occurred in six patients, resulting in an 8% major complication rate. Two patients in whom major complications developed were part of the group of only four patients for whom ablation was performed for tumors > 7 cm in diameter. There were no procedural-related deaths. No evidence for local tumor recurrence was identified in any patients with follow-up contrast-enhanced CT or MRI obtained 3 months or longer from the time of the ablation. Follow-up in these patients averaged 15 months (range 3-42 mos).

CONCLUSION

Percutaneous cryoablation of renal masses >or=3 cm in diameter can be performed with high technical success and low complication rates. Extra scrutiny is needed during cryoablation of central renal masses to make sure the ablation zone extends to include the deepest margin of the tumor. Although our experience is limited, percutaneous cryoablation of renal tumors > 7 cm in diameter may be associated with increased complications. The lack of local renal tumor recurrences seen in this study on short-term follow-up is encouraging, but long-term follow-up remains necessary to ensure treatment durability.

Long-term results after computed-tomography-guided percutaneous radiofrequency ablation for small renal tumors

PURPOSE

To present the long-term results and to identify possible risk factors for recurrence after radiofrequency ablation (RFA) for renal tumors.

PATIENTS AND METHODS

Thirty-one patients with a total of 39 renal tumors ranging from 1.3 to 7.5 cm (mean size 3.1 cm) were treated with RFA using a Rita Medical System model 1500 RF generator attached to a 15-gauge Starburst XL probe under percutaneous CT scan guidance. The average patient age was 61.4 years (range 37-86 y). Indications for RFA were bilateral tumors, presence of serious comorbidities, a high risk of development of additional renal-cell carcinomas, marginal renal function, and patient preference. No tumor was biopsied before treatment; therefore, only local control success rates could be provided. Recurrence was defined as enhancement or lesion enlargement on follow-up CT scan. Statistical analysis was performed to identify possible risk factors for recurrence. Parameters tested were age, sex, and number of ablation sessions, tumor size, location, multiplicity, body mass index, and American Society of Anesthesiologists score.

RESULTS

Initial ablation success rate was 90% and with repeated treatment, a success rate of complete ablation reached 97%. Average follow-up was 61.2 months (range 36-84 mos). Recurrence was seen in four tumors. The risk factor associated with recurrence was tumor size exceeding 4 cm (P < 0.01, relative risk [RR] = 3.31). Overall 3- and 5-year tumor control rate was 92% and 89%, respectively. Tumor size was also predictive for recurrence in the subgroup of 17 patients followed for more than 5 years (P = 0.02, RR = 3.15). Tumor control rate for this subgroup was 90%.

CONCLUSIONS

According to our results, larger tumor size was prognostic for recurrence after RFA for renal tumors. This treatment seems to demonstrate excellent tumor control long-term results, comparable to those achieved by nephron-sparing surgery in a selected group of patients.

Radio frequency ablation of renal tumors in patients with metastatic renal cell carcinoma

PURPOSE

We retrospectively evaluated the feasibility, safety and outcomes of radio frequency ablation of primary renal tumors to control local disease while preserving renal parenchyma in a series of patients with metastatic renal cell carcinoma in a single institutional, multidisciplinary setting.

MATERIALS AND METHODS

We evaluated the records of patients with metastatic renal cell carcinoma who underwent percutaneous radio frequency ablation of a primary renal tumor. Patient demographic and disease characteristics, adjunctive medical and surgical therapies, recurrence and clinical outcomes were studied.

RESULTS

A total of 15 patients treated between 2002 and 2008 met study inclusion criteria. There was no incomplete ablation or local recurrence. Ten patients had biopsy proven renal cell carcinoma in the ablated renal mass. Eight patients had a solitary metastasis, 3 had metastasis at 2 sites and 4 had 3 or more metastatic sites. Four patients experienced major complications. Median radiographic and clinical followup in patients at risk for an event was 25.5 and 33.0 months, respectively. The overall survival rate 1, 3 and 5 years after radio frequency ablation was 73.3%, 57.1% and 38.1%, respectively. At last evaluation 4 patients were in complete remission, 4 had no evidence of local recurrence but had evidence of distant disease and 7 had died of the disease.

CONCLUSIONS

Radio frequency ablation is feasible and safe in highly selected patients with metastatic renal cell carcinoma, resulting in durable local control as part of multimodality management and achieving renal preservation. Further investigation is required to define the role of radio frequency ablation in this patient population.

The importance of nephron-sparing focal therapy: renal function preservation

Historically, renal cancer has been treated with radical nephrectomy. Consequently, many patients developed renal insufficiency and the health problems associated with this. With the increasing diagnosis of small renal masses, nephron-sparing treatments have been developed to treat these masses adequately, while maximizing renal function. Focal ablative therapy is a means to treat small renal masses in a minimally invasive manner. Yet, there are few studies that have focused on their ability to preserve renal function. In this article, we review the existing literature on the renal function outcomes of patients treated with either radio frequency ablation or cryoablation.

Results of radiofrequency kidney tumor ablation: renal function preservation and oncologic efficacy

OBJECTIVES

Radiofrequency ablation (RFA) is increasingly finding a place in the treatment of small renal masses (SRM). RFA may be able to provide better renal preservation, while achieving appropriate cancer control. This investigation takes a critical look at pertinent aspects of RFA principles and reviews oncological and renal function outcomes.

METHODS

A review of the most current English literature using a PubMed search was done. Oncological and renal function outcomes were reviewed from selected articles published between 2003 and 2009. Oncological outcome was determined by "single treatment" success rate at first follow-up and "After single treatment" success rate after first follow-up. Renal function outcome was determined by either change in creatinine, creatinine clearance, or GFR after RFA.

RESULTS

The mean tumor size was 2.5 cm for 16/17 studies. Average mean and median follow-up was 23.3 months in 13/17 studies and 19.8 months for 4/17 studies. "Single Treatment" success rates of 90-100% (average = 97.2%) were noted in 13 studies. Average increase in serum creatinine was +0.14 mg/dL in four studies. Serum creatinine and creatinine clearance change in one solitary kidney study was +11 mmol/L and -8 mL/min., respectively.

CONCLUSIONS

RFA is fast emerging as a safe and efficacious treatment for small renal masses. Compared to extirpative treatment options, RFA seems to provide the lowest rate of renal impairment, while providing acceptable rates of tumor ablation. As long-term results emerge, this may become one of the treatment modalities for renal tumors in patients with solitary kidneys and renal impairment.