Ablation of Small Renal Masses: Practice Patterns at Academic Institutions in the United States

Abstract

Purpose:

We aimed to determine the current practice patterns at academic institutions in the use of ablative technologies for the management of small renal masses.

Patients and Methods:

Mail surveys were sent to 124 academic institutions in the United States. The survey consisted of 12 questions pertaining to institutional demographic information, the use of ablation technology for small renal masses, the role of the urologist in ablation, and biopsy preferences prior to treatment.

Results:

The overall response rate was 52% (64/124). Ablation was offered by all of the academic centers that responded to the survey and included 73% percutaneous cryoablation, 52% percutaneous radiofrequency ablation, 83% laparoscopic cryoablation, and 20% laparoscopic radiofrequency ablation. Eighty-eight percent of institutions performed one to five total ablation procedures each month. Urologists alone performed 13% of ablation procedures, radiologists performed 45% of ablation procedures, and a combined approach (urologist and radiologist present) was used in 43% of the institutions. When questioned about their role during percutaneous ablation, we found that urologists were present at the time of ablation in 59% of institutions, in 32% of institutions urologists placed the needles for ablation, and in 98% of institutions urologists were responsible for the postoperative care of the patient. Eighty-nine percent of academic institutions performed a biopsy of the renal mass with 67% performing a core biopsy, 5% performing a fine-needle aspiration (FNA), and 28% performing both a core biopsy and FNA. Nineteen percent of institutions performed a renal mass biopsy prior to the day of the procedure so that the pathology was known prior to ablation.

Conclusions:

Ablative technologies are well utilized for the treatment of small renal masses at current academic institutions with urologists directly involved in the ablation procedure in only half of the institutions. While preablation biopsy is common, pathology is rarely known prior to ablation.

Introduction

T he increased use of noninvasive abdominal cross-sectional imaging has contributed to an increase in the diagnosis of small renal masses.^1,2 Nephron-sparing surgery (partial nephrectomy) has been shown to confer equivalent oncologic and superior renal function outcomes compared with radical nephrectomy for renal tumors <4 cm.^3
–5 However, nephron-sparing surgery is not without associated perioperative complications and patient morbidity.⁴ This has led to an increased utilization of less-invasive laparoscopic or percutaneous thermal ablative procedures [cryoablation or radiofrequency ablation (RFA)].⁶ Further, with the publication of the AUA Guideline for Management of the Clinical T₁ Renal Mass in 2009, a greater emphasis was placed on the utilization of nephron-sparing options, including active surveillance, partial nephrectomy, and thermal ablation, in order to preserve long-term renal function.⁴ The purpose of our study was to determine the current practice patterns at academic institutions in the United States in the use of ablative technologies for the management of small renal masses (<4 cm).

Patients and Methods

Mail surveys were sent to the urology department of 124 academic institutions (all departments had a urology residency program) in the United States on January 2011. The survey consisted of 12 questions pertaining to institutional demographic information, the use of ablation technology for small renal masses, the role of the urologist in ablation, and biopsy preferences prior to treatment (Tables 1 and 2). The survey was validated for face and content validity using a small focus group of urologists. The survey was limited to 12 questions and used closed format questions to minimize the time it took to complete the survey with the goal of maximizing the survey response rate.⁷ The mail survey responses were returned anonymously and the results of the survey were then tabulated and descriptive statistics were used to analyze practice trends in the ablation of small renal masses at U.S. academic centers.

Table 1.

Ablation Procedures Offered at Responding Academic Institutions

PC	LC	PRFA	LRFA	No. (%)
				7 (11%)
				11 (17%)
				1 (2%)
				2 (3%)
				24 (38%)
				2 (3%)
				1 (2%)
				2 (3%)
				4 (6%)
				4 (6%)
				6 (9%)
47/64 (73%)	53/64 (83%)	33/64 (52%)	13/64 (20%)

Darkened cell represents ablation procedure offered.

PC=percutaneous cryoablation; LC=laparoscopic cryoablation; PRFA=percutaneous radiofrequency ablation; LRFA=laparoscopic radiofrequency ablation.

Table 2.

Survey Results

Number of total ablation procedures performed per month	%
1–5	88% (56/64)
6–10	11% (7/64)
11–15	1% (1/64)
>15	0% (0/64)
Who performs the percutaneous ablation procedures
Urologist	13% (8/64)
Radiologist	45% (29/64)
Combined approach	42% (27/64)
Role of urologist in percutaneous ablation procedures
Urologist present in the room during ablation	59% (32/64)
Urologist places needles for ablation	32% (17/64)
Urologist is responsible for postoperative care of patient	98% (63/64)
Imaging study used to identify and monitor tumor during percutaneous ablation
CT scan	59% (37/64)
MRI	6% (4/64)
Ultrasound	13% (8/64)
Combination of CT and ultrasound	22% (15/64)
Combination of MRI and ultrasound	0% (0/64)
Do you perform a biopsy of the renal mass prior to ablation?
Yes	89% (57/64)
No	11% (7/64)
■ If yes, when is the biopsy performed?
Renal mass biopsy is performed prior to the day of the procedure so that the pathology is known.	19% (11/57)
Renal mass biopsy is performed on the day of the procedure prior to ablation.	81% (46/57)
■ If yes, what type of biopsy is performed?
Core biopsy	67% (38/57)
FNA	5% (3/57)
Both a core biopsy and FNA	28% (16/57)

CT=computed tomography; MRI=magnetic resonance imaging; FNA=fine-needle aspiration.

Results

The overall response rate was 52% (64/124). Ninety-seven percent (62/64) of responding institutions were academic/university practices and the remaining 3% (2/64) were federal/military institutions. Fifty percent (32/64) of responding institutions were located in large metropolitan cities, 41% (26/64) in urban cities, and 9% (6/64) in rural towns. Thermal ablation for the management of small renal masses was offered by all of the institutions that responded to the survey.

Ablation modalities offered were as follows: 73% percutaneous cryoablation (PC), 52% percutaneous RFA (PRFA), 83% laparoscopic cryoablation (LC), and 20% laparoscopic RFA (LRFA) (Table 1). The results of the survey are reported in Table 2. Eighty-eight percent of institutions performed one to five total ablation procedures each month. Urologists alone performed 13% of ablation procedures, radiologists alone performed 45% of ablation procedures, and a combined approach (urologist and radiologist present) was used in 43% of the institutions. When questioned about their role in percutaneous ablation procedures, we found that urologists were present at the time of ablation in 59% of institutions, in only 32% of institutions did the urologist place the needles for ablation, and the urologist was responsible for the postoperative care of the patient at all of the institutions. Eighty-nine percent of academic institutions performed a biopsy of the renal mass with 67% performing a core biopsy, 5% performing a fine-needle aspiration (FNA), and 28% performing both a core biopsy and FNA. Nineteen percent of institutions performed a renal mass biopsy prior to the day of the procedure so that the pathology was known prior to ablation and 81% biopsied the renal mass on the day of the procedure.

Discussion

The incidence of small renal masses has increased with the increased utilization of abdominal cross-sectional imaging.² Studies have shown that radical nephrectomy predisposes patients to chronic kidney disease and increased mortality.^5,8 Thus, surgical excision via partial nephrectomy has become the standard of care for the treatment of clinical T_1a (≤4 cm) renal mass in most healthy patients.⁴ However, thermal ablation and active surveillance have evolved as viable options for the management of the small renal mass because of the potential for less damage to renal function and less perioperative pain and morbidity.

Our previous survey, performed in 2006, showed that thermal ablation was offered by 93% of responding academic centers, with cryoablation (79%) being more frequently utilized than RFA (55%).⁹ The lack of sufficient efficacy data was the most prevalent reason (80%) for not offering ablation at that time. Our current survey (2011) results showed that all responding centers offered ablation, illustrating that thermal ablation has become a well-accepted modality in the armamentarium of treatment options for the small renal mass. Cryoablation (73% PC; 83% LC) continues to be utilized more frequently than RFA (52% PRFA; 20% LRFA) at academic institutions.

Choueiri et al. evaluated national practice pattern trends in the use of thermal ablation from 2004 to 2007 for the management of stage I renal cell cancer using the Surveillance, Epidemiology, and End Results (SEER) database and found an increase in the use of both partial nephrectomy and thermal ablation during that time period.⁶ They also found that older age was associated with use of thermal ablation, possibly because of perceived short-term equivalent oncologic efficacy or due to selection of patients with higher risk of comorbidities.^3,6 Smaller tumor size was also associated with an increased use of thermal ablation versus partial nephrectomy or radical nephrectomy.^3,6 In the 2006 survey, 85% of academic departments performed less than five ablation cases per month. Our current survey has shown that the average number of ablations performed per month at academic institutions has remained stable with 88% of institutions performing 1 to 5 ablations per month and 11% performing 6 to 10 thermal ablations per month.

A cost analysis comparing LC, PC, LRFA, and PRFA may be important as long-term oncologic and safety outcomes of these nephron-sparing approaches improve and become comparable to open partial nephrectomy (OPN) and robotic partial nephrectomy. Castle et al. performed a cost comparison of 173 patients diagnosed with a solitary cT_1a renal mass who underwent treatment via OPN, robotic-assisted partial nephrectomy (RLPN), LRFA, or computed tomography guided radiofrequency ablation (PRFA).¹⁰ Median total costs (included surgical costs, hospital stay, and 6-month follow-up) for OPN (n=52), RLPN (n=48), LRFA (n=44), and PRFA (n=29) were $17,018, $20,314, $13,965, and $6,475, respectively. Total costs at 6 months for nephron-sparing surgery were lowest for PRFA and LRFA compared with RLPN and OPN.

In the past, collaboration between radiologists and urologists during the thermal ablation procedure occurred in 51% of institutions, with urologists alone performing ablation in 35% of institutions and radiologists alone performing ablation in only 13% of institutions.⁹ When examining the role of the urologist and radiologist during percutaneous ablation procedures, we found that in 42% of institutions radiologists and urologists collaborated on the procedure and in 45% of the institutions radiologists alone performed the ablation procedures. Even though the urologist was regularly present in the room at the time of percutaneous ablation in 59% of institutions and placed needles for ablation in 32% of institutions, the urologist was responsible for the postoperative care of the patient in 98% of the academic institutions. Computed tomography and a combination of computed tomography with ultrasound were the most common imaging modalities used to identify and monitor tumors during percutaneous ablation.

The potential for aggressive behavior in clinical stage T₁ tumors is heterogeneous, with 20% of tumors considered benign and only 20% to 25% of tumors exhibiting potentially aggressive behavior at the time of diagnosis.^4,11

–14 In the AUA Guideline for Management of the Clinical T₁ renal mass, the panel consensus standard recommendation was that tumor biopsy (recommended core biopsy for better diagnostic accuracy) should always be performed prior to thermal ablation in order to define histology and should also be considered after treatment if there is any suspicion of recurrence.⁴ Barwari et al. sent a questionnaire to members of the Endourological Society to assess the use of renal mass biopsy in current urologic practice.¹⁵ Despite a low response rate (10.2%, 190 responders), they found that 73% of responders “never” or “rarely” performed a renal mass biopsy. Tan et al. evaluated patient and tumor characteristics associated with percutaneous renal mass biopsy among patients with small renal masses at a single institution. They found that 38% of patients presenting with a renal mass at their academic institution underwent a renal mass biopsy and that biopsy was most commonly performed in patients with complicated anatomic or tumor characteristics (larger tumor size, solitary kidney, juxta-hilar tumor location, and high complexity nephrometry score).¹⁶

In our survey, which was specific to thermal ablation, 89% of responding institutions performed a biopsy of the renal mass prior to ablation. The diagnostic yield for core-needle biopsy with or without FNA has been shown to provide accurate diagnosis in >90% of renal masses.¹⁷ In the setting of the small renal mass, percutaneous core-needle biopsies have been shown to yield a diagnosis in >80% of cases.¹⁸ Barwari et al. reported that 61% of respondents preferred core biopsies, 8% cytological aspiration, and 31% performed both core biopsies and cytology. These results were similar to the results in our survey where 67% of responding institutions performed core biopsies, 5% performed FNA, and 28% performed both core biopsy and FNA.¹⁵ Ninety-five percent of the institutions in our study and 92% of respondents in the study by Barwari et al. who performed a biopsy of the tumor used core biopsy or a combination of core biopsy with FNA. In our survey we also asked when the biopsy was performed (prior to the day of the procedure or on the day of the procedure prior to ablation) to determine whether knowledge of the biopsy result was known prior to thermal ablation. Eighty-one percent of institutions performed their renal mass biopsy on the day of the procedure prior to ablation so that pathology was not known. This finding would suggest that, in the majority of institutions, thermal ablation is performed for small renal masses independent of pathology possibly because 75% to 80% of small renal masses are either benign or low-grade renal cell carcinoma.

Limitations of our survey include possible overestimation of the use of thermal ablation as those institutions not responding to the survey may not be performing ablative therapies for the treatment of the small renal mass. Our surveys were only sent to academic urology departments and thus interventional radiologists were not surveyed. Thus, those programs with collaborative practices may have been more likely to respond to our survey and programs where only interventional radiologists perform thermal ablation may have been less likely to respond. We deliberately created a short survey in order to maximize the response rate; thus, we were unable to investigate the rational for why institutions did not perform renal biopsies or the specifics behind the tumor size or patient populations treated for each of the thermal ablation modalities used. Our survey focused on the use of thermal ablation in the academic setting in the United States; thus, we cannot comment on the use of thermal ablation by private practice urologists or in an international setting. Despite our study limitations, our study illustrates that ablative technology is utilized in the majority of academic institutions in the United States and helps to elucidate the current role of the urologist in percutaneous ablation as well as the utilization of renal mass biopsy prior to thermal ablation.

Conclusions

Our survey of academic urologists shows that ablative technologies are well utilized for the treatment of small renal masses at current academic institutions with urologists directly involved in the ablation procedure in only half of the institutions. While preablation biopsy is common, pathology is rarely known prior to ablation.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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