Kidney Radiofrequency Ablation for Small Renal Tumors: Oncologic Efficacy

Safety, efficacy and predictors of local recurrence after percutaneous radiofrequency ablation of biopsy-proven renal cell carcinoma

PURPOSE

To evaluate the safety and efficacy of percutaneous radiofrequency ablation (RFA) for localised renal cell carcinoma (RCC) and examine potential associations between age, gender, tumour size, location, chronic kidney disease, comorbidities, learning curve and local recurrence.

METHODS

We retrospectively analysed survival outcomes for patients with biopsy-proven RCC treated by RFA at Westmead Hospital. Complication data were gathered from all patients that underwent renal RFA. 3 and 5 year local recurrence-free (RFS), disease-free (DFS) and overall survival (OS) outcomes were reported. Univariate and multivariate analysis was used to examine each potential predictor.

RESULTS

A total of 168 patients were eligible for the study. Forty-eight patients with biopsy-proven RCC had minimum 3-year follow-up. Our complication rate was 1.2 % (2/168) and local recurrence rate 10.4 % (5/48). Five-year RFS, DFS and OS were 86.8, 82.3 and 92.6 % on a median 4.1-year follow-up (IQR 3.4-4.9). None of the patient or tumour-specific characteristics were associated with RFS.

CONCLUSION

Radiofrequency ablation performed at our centre was a safe and effective procedure with low complication rates and durable RFS. Tumour characteristics, comorbidities and learning curve were not associated with local recurrence.

Thermal Ablation of Renal Tumors: Indications, Techniques and Results

BACKGROUND

About 15,000 persons receive the diagnosis of kidney cancer in Germany every year. Surgical resection is the standard treatment for locally confined tumors, but minimally invasive thermoablative techniques are increasingly being used as well.

METHODS

This article is based on publications retrieved by a selective literature search in PubMed regarding the thermoablative techniques now used in clinical practice, with particular attention to radiofrequency ablation (RFA) and cryoablation (CA).

RESULTS

RFA and CA are suitable for patients who cannot undergo surgery because of comorbid illnesses or who have contralateral recurrences or a hereditary precancerous condition. The primary technical success rate of these procedures ranges from 88% to 100%. More than 95% of tumors under 3 cm in diameter can be completely ablated. Reported complication rates range from 1% to 7%. New data on long-term outcomes reveal metastasis-free survival rates of 88% to 99% five years after ablation. A major advantage of these procedures is that thermoablation does not impair renal function to any relevant extent and is thus a good option for patients with limited renal function or a single kidney.

CONCLUSION

The thermoablative techniques are an important addition to the armamentarium of effective treatments for locally confined renal tumors. The guidelines of the American and European urological societies now list thermoablation with RFA or CA as an option for the treatment of small renal tumors with curative intent. Thermoablation of renal tumors has not yet been studied in randomized controlled trials; these will be needed so that the efficacy of tumor control, survival rates, complication rates, and quality of life after treatment can be reliably evaluated to provide definitive confirmation of the value of interstitial techniques.

Renal tumor ablation

Percutaneous, image-guided ablation for renal cell carcinoma (RCC) is an important treatment option for many patients. With more than 60,000 new cases every year and nearly three-fourths of those presenting as stage 1A, minimally invasive, nephron-sparing therapies have become the standard of care. Stage 1 A (<4cm, organ confined) disease presents the best scenario for percutaneous ablation. Various other factors influence the decision-making tree, such as patient age, life expectancy, comorbid condition, renal function, and the risk of metachronous lesions. Preparation aims at minimizing risks and has been discussed in detail. Computed tomography guidance remains the best option, and conscious sedation is adequate for most cases. Ultrasound and more recently magnetic resonance guidance are becoming viable alternatives. Whether radiofrequency or cryoablation are chosen, a margin of at least 5mm and up to 10mm is recommended. Various maneuvers required for optimum outcome, including hydrodissection and preoperative embolization are also discussed. Most renal ablations can be performed on an outpatient basis. Reasons to admit include complications, high-risk patients, and the need for symptom management. Follow-up aims at (1) ensuring complete ablation and (2) monitoring against a metachronous lesion. For the former, a 3-month contrast computed tomography or magnetic resonance imaging is required and for the latter an annual examination is recommended. Though partial nephrectomy remains the gold standard, image-guided, percutaneous ablation for RCC can result in very similar outcomes. Over the last 10 years, there have been numerous studies reporting the efficacy and safety of ablation, and more recently, long-term studies have confirmed those numbers. Overall, the efficacy for percutaneous ablation for RCC stands at 90%-95% with a complication rate of 6%-7%. The most important factors for positive outcome are patient or tumor selection and operator experience.

Evaluation of a bipolar-cooled radiofrequency device for ablation of bone metastases: preclinical assessment in porcine vertebrae

BACKGROUND CONTEXT

Cancer spread to the spine affects bone stability and can lead to pathologic fracture and neurologic impairment. Radiofrequency ablation (RFA) recently has gained popularity in treating skeletal tumors. Conventional RFA devices use a monopolar design, which limits the ability to comprehensively treat large tumors in bony tissues and may pose risks to adjacent critical normal neurologic tissues when applied to vertebrae. New bipolar-cooled radiofrequency (BCRF) may generate larger controlled lesions without the same degree of risk to adjacent structures.

PURPOSE

The purpose of this study was to evaluate the feasibility, efficacy, and safety of RFA with the use of a new bone-specific, BCRF probe in a porcine vertebral model and to evaluate the ability of magnetic resonance (MR) imaging to represent histologic outcomes of RFA treatment.

STUDY DESIGN

Basic science: preclinical in vivo study.

METHODS

RFA was evaluated in three noncontiguous lumbar vertebrae in six Yorkshire pigs (25-30 kg). Via a transpedicular approach for probe placement, two vertebrae received BCRF treatment and one vertebrae served as a sham control. MR imaging and neurological assessments were conducted pre- and posttreatment as well as immediately before animal sacrifice (n=3 at day 0, n=3 at day 14). MR ablation zones were compared with hematoxylin and eosin-stained histological sections.

RESULTS

With BCRF, large reproducible zones of ablation were achieved, confined within the vertebrae, without damage to adjacent tissues or the spinal cord. All animals demonstrated normal consistent neurologic behavior pre- and posttreatment. External tissue temperatures around targeted vertebrae were not increased. MR imaging after 14 days was more effective in demonstrating ablation effects than images on day 0, with radiologic findings most apparent on T2-weighted sequences. Histologic analysis of samples corresponded well to the zones of ablation observed on MR images (R=0.9, p<.01).

CONCLUSIONS

The study demonstrated feasibility, safety, and effectiveness of BCRF ablation of vertebral bone. This motivates ongoing preclinical evaluation in diseased models to further explore the potential for its use in clinical treatment of metastatic vertebrae.

[Small renal masses: 10 years of treatment in a tertiary referral center in cancer research]

OBJECTIVES

To analyze the impact of preoperative clinical data that could influence the undertaking of small renal masses (size<4cm) and to direct patients towards surgery or observance or radiofrequency.

PATIENTS AND METHODS

From January 2000 to December 2010, 253 small renal masses were included in a retrospective study. Renal masses less than 3cm were compared to the 3 to 4cm masses. Clinical data, pathological data and follow-up was noted prospectively on the database and we analyzed it according to the treatment done (surgery, radiofrequency or observation).

RESULTS

Surgical treatment, radiofrequency and observation were performed for 214 (86.4%), 15 (5.9%), and 24 (9.5%) patients respectively. The treatments of the patients differed in the two groups (<3cm vs. 3-4cm) and the appeal to radiofrequency and observation was more frequent for elder patients (>65years old) and for those whom performance status (ECOG status) greater or equal to 1. Cancer specific survival was not statistically different for the two groups (average: 87.5% after 5years, mean 33months follow-up, P=0.7). Independent risk factors of recurrence were Fuhrman grade, synchronous tumors, noddles invasion and metastatic progression. Positive surgical margins were not a risk factor of recurrence (P=0.6).

CONCLUSION

Age and performance status are the two main clinical data, which influence the treatment for patients with small renal masses. Radiofrequency and observation were undertaken more regularly for elder and altered ones. The use of scales as Charlson Index or Lee scale could help to choose more easily according to global morbidity and mortality.

Radiofrequency ablation of incidental benign small renal mass: outcomes and follow-up protocol

OBJECTIVE

To review our 10-year experience with radiofrequency ablation, focusing on the outcomes for the incidental benign renal tumor. Tumor ablation is an alternative minimally invasive approach for the treatment of small renal masses (SRMs), with published series appropriately emphasizing the outcomes for the renal cell carcinoma subset of treated tumors. However, just as with partial nephrectomy, approximately 20% of SRMs are benign. The intermediate- to long-term outcome of the incidentally ablated benign tumor and its appropriate follow-up protocol is unknown.

METHODS

All SRMs treated with temperature-based radiofrequency ablation from 2001 to 2011 were reviewed. Of a total of 280 enhancing SRMs biopsied at radiofrequency ablation, 47 were confirmed as benign tumors. Ablation success was defined as the lack of enhancement on the initial postablation axial imaging. Recurrence was defined as tumor growth and enhancement on follow-up axial imaging.

RESULTS

Of the 47 benign tumors, 32 were treated percutaneously and 15 laparoscopically. The histologic biopsy finding was angiomyolipoma in 10 and oncocytoma in 37. The median tumor size was 2 cm (range 1-3.6), and the mean follow-up was 45 months. No recurrences developed, and all lesions required only 1 treatment session. The median pre- and postoperative glomerular filtration rate was 77 mL/min/1.73 m(2) (range 39-137) and 68 mL/min/1.73 m(2) (range 36-137). The present study was limited by its retrospective nature and small sample population.

CONCLUSION

Radiofrequency ablation of SRMs <3.5 cm found to be benign on concurrent biopsy can be efficaciously treated with a single treatment session. Long-term follow-up imaging might not be required if successful ablation is determined at the initial post-treatment cross-sectional imaging study.

Radiofrequency ablation of small renal masses as an alternative to nephron-sparing surgery: preliminary results

Introduction

Radical endoscopic minimal-invasive treatment methods, such as thermal ablation, are sought as an alternative to standard radical surgical treatment of kidney neoplasms. We analysed patients who could be qualified for radical treatment due to T1a renal tumour.

Material and methods

Twenty-three patients out of 129 who underwent radiofrequency thermal ablation of kidney tumours in the years 2003-2010 were analysed. The inclusion criteria were age below 70 years, lack of major comorbidities (ASA score 1, 2), and competent contralateral kidney. In all cases tumour size was below 4 cm. All patients were followed up with computed tomography (CT) and ultrasonography (USG) every 6 months for 3 years.

Results

In 20 patients kidney tumour was biopsied before radiofrequency ablation (RFA) and 10 of these biopsies were positive and revealed cancer. Six patients required additional treatment due to recurrence visible in CT – 3 with a positive biopsy result, 1 with negative and 2 without biopsy. Three of them were treated with a second session of RFA, 1 with radical nephrectomy and 2 with partial nephrectomy. No disease dissemination was observed and all patients who received additional treatment remain disease free.

Conclusions

The RFA can be safely used in selected patients with T1a tumour as an alternative to partial nephrectomy. Careful follow-up is required after thermal ablation and allows early detection and successful treatment of recurrences.

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.

Radiofrequency ablation: a minimally invasive approach in kidney tumor management

The management and diagnosis of renal tumors have changed significantly over the last decade. Due to advances in imaging techniques, more than 50% of kidney tumors are discovered incidentally and many of them represent an early stage lesion. This has stimulated the development of nephron-sparing surgery and of the minimally invasive treatment options including ablative techniques, i.e., radiofrequency ablation (RFA) and cryoablation. The objective of the minimally invasive approach is to preserve the renal function and to lower the perioperative morbidity. RFA involves inducing the coagulative necrosis of tumor tissue. Being probably one of the least invasive procedures in kidney tumor management, RFA may be performed percutaneously under ultrasound (US), computed tomography (CT) or magnetic resonance (MR) guidance. Most of the studies show that the RFA procedure is efficient, safe and has a low complication rate. Due to the still limited data on the oncological outcome of RFA, the indication for this intervention remains limited to selected patients with small organ-confined renal tumors and contraindication to surgery or who have a solitary kidney. The aim of our study is to review the literature on RFA of kidney tumors.