outcomes following ct-guided percutaneous radiofrequency ... · carcinoma, renal cell carcinoma,...

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E18April 2014 • InterventionalOncology360.com

Outcomes Following CT-Guided Percutaneous Radiofrequency Ablation of Primary Renal TumorsNancy Lee, MS1; John H. Rundback, MD2; Kevin Chaim Herman, MD2; John Kerns, MD2; Ravit Barkama, MD2

From the 1George Washington University School of Medicine and Health Sciences, Washington, DC,

and the 2Interventional Institute, Holy Name Medical Center, Teaneck, New Jersey.

Abstract: Purpose: The purpose of this study was to analyze outcomes in a single-center cohort of patients undergoing CT-guided percutaneous renal radiofrequency ablation (rRFA) to determine if lesion size was a dif-ferentiator of outcomes, and to describe the temporal changes in lesion size following rRFA. Materials and Methods: Forty lesions in 37 patients (27 males, 10 females; mean age 70±13 years) were treated with rRFA from 2006 to 2013. Patient, tumor, and treatment characteristics were analyzed. Statistical analysis included the entire treated cohort with particular attention paid to subgroupings based on (a) whether patients had a renal mass <3 cm or ≥3 cm, and (b) whether the lesion was biopsy-proven renal-cell carcinoma (RCC). To evaluate lesion changes after ablation, a mixed-effects ANOVA model was fit to lesion size values over time. Results: Kaplan-Meier survival curves showed trends toward worse primary recurrence and overall survival in lesions ≥3 cm, but these were not statistically significant (P=.13 and P=.27 respectively). Secondary recurrences were the same in both groups. The rate of change over time in lesion size following rRFA did not differ significantly either by initial lesion size (P=.65), or between biopsy-proven and non-biopsy-proven RCC (P=.46). Conclusion: rRFA is safe and effective in treating kidney tumors. Overall success of tumor ablation was unrelated to initial size. Serial changes in tumor size after ablation are similar regardless of original size and whether the lesion had been proven RCC by biopsy.

Key words: carcinoma, renal cell carcinoma, radiofrequency ablation.

Renal cell carcinoma (RCC) constitutes

the majority of kidney malignancies.1 The

number of RCC cases is increasing with

approximately 65,000 new cases diagnosed each year

in the United States.1,2 Almost twice as many men as

women are diagnosed with RCC, and the age at di-

agnosis peaks between ages 50 and 80 years.2,3 Ciga-

rette smoking and obesity have consistently been es-

tablished as risk factors.1

Guidelines indicate active surveillance, surgical in-

tervention, and minimally invasive therapy as manage-

ment methods for RCC.4 Renal radiofrequency abla-

tion (rRFA) is a favorable alternative in patients who

are poor surgical candidates because it spares kidney

tissue and retains renal function. Renal radiofrequency

ablation has no negative effects on glomerular filtra-

tion rate in the short or intermediate term,5 and it also

poses less risk for developing chronic kidney disease

(CKD) when compared to radical nephrectomy.6,7

Many studies have shown high clinical success rates

Rundback_v.indd 18 4/16/14 4:25 PM

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April 2014 • InterventionalOncology360.com E19

for rRFA, especially in cases where the lesions are

exophytic and <3 cm8-11 or <4 cm.12-15 The purpose of

this study was to analyze outcomes in a single-center

cohort of patients undergoing CT-guided rRFA, to

determine if lesion size was noted to be a differentia-

tor of outcomes, and to describe temporal changes in

lesion size following rRFA in patients with smaller vs

larger tumors.

MATERIALS AND METHODSPatient and Tumor Characteristics

IRB approval was obtained for this study. A retro-

spective review was performed of our single institu-

tional experience performing CT-guided percuta-

neous RFA. From June 2006 to June 2013, 40 renal

masses in 37 patients (27 males, 10 females; mean age,

70±13 years; range, 40-89 years) were ablated. One

patient had bilateral tumors; another patient had 3 tu-

mors (1 on the right kidney, 2 on the left kidney).

Four patients had previous partial nephrectomy. Pa-

tient characteristics are summarized in Table 1.

Tumor size ranged from 1.2 cm to 6.3 cm (mean,

2.9±1.1 cm). Nineteen lesions (7 clear cell, 6 papillary,

2 chromophobe, 2 mixed, 3 unspecified) were con-

firmed to be RCC by image-guided biopsy. Similar

to our experience, routine biopsy prior to rRFA is of-

ten not performed.6,10,12-14 Two lesions were parapelvic

(central), and 38 lesions extended to the renal cortex

(exophytic). Additional tumor characteristics are listed

in Table 2.

Percutaneous rRFA Procedure

Prior to the procedure, informed consent was ob-

tained from all patients. With patients under general

endotracheal or laryngeal mask anesthesia and lying

prone on the CT table, scanning was performed to de-

termine the exact location of the lesions. The method

of anesthesia was at the discretion of the treating an-

esthesiologist. Appropriate skin sites for ablation were

prepped and draped in standard sterile fashion and lo-

cally anesthetized with 1% lidocaine. Under direct CT

guidance, electrodes (range, 2.5 cm to 5 cm active tip)

were inserted into the lesions (Figure 1). The elec-

trodes were multitined in 32 cases (LeVeen; Boston

Scientific) and Cool-Tip in 8 cases (Covidien). Ad-

justments were made to confirm precise positioning

of the needle within the mass. Aside from variations in

technique of each performing radiologist, manufac-

turer instructions were followed for power and abla-

tion time (mean, 21±10 minutes).

With LeVeen probes, ablations were performed un-

til roll-off was achieved using a 200-watt generator;

a second ablation was performed starting at 70% of

the initial maximal ablation energy according to treat-

ment guidelines until roll-off occurred. Tumors ≥3 cm

were treated with overlapping lesions, often deep and

centrally within the mass. After retracting and remov-

ing the needles, CT scanning was performed to evalu-

ate for any procedural complications. Streaking in the

perirenal fat and the presence of gas bubbles in the

ablated bed provided indication of ablation efficacy

on noncontrast study. Patients were extubated prior

to transfer to the recovery room. Treatment characters

are listed in Table 3.

Patient Follow-Up

Patients were scheduled for a pre- and post-con-

trast CT scans at 1, 3, and 6 months after the proce-


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dure followed by planned annual imaging for 5 years.

Variations existed depending upon patient availabil-

ity, scheduling conflict, and patient’s ability to receive

iodinated contrast. The mean duration of follow-up

for all patients was 19.3±17.5 months (median, 14.1

months). Twenty patients were followed up with dual-

phase CT,5 with noncontrast CT alone,8 with MRI,

and 1 with PET CT. Two patients were lost to follow-

up, while 1 patient had not yet reached the 1-month

follow-up point.

Analysis & Statistics

The analysis included the entire treated cohort, with

particular attention paid to subgroupings based on (a)

whether patients had a renal mass <3 cm (Group 1)

or ≥3 cm (Group 2) and (b) whether or not the lesion

was biopsy-proven RCC. Student t test, Fisher exact

test, and chi-square test were performed via MedCalc

to compare patient, lesion, and treatment character-

istics between Groups 1 and 2. Kaplan-Meier (KM)

survival curves were also created via MedCalc to ana-

lyze primary recurrence and overall survival.

To evaluate lesion changes over time after rRFA, a

mixed-effects ANOVA model was fit to lesion size val-

ues over time. Fixed effects included a separate inter-

cept for each subgroup and a separate slope over time

for each subgroup. Random effects included the ran-

dom effect for patient nested within subgroup and a

random slope over time for each patient nested within

subgroup. An intercept for the overall population was

estimated as the equally weighted average of the inter-

cept over the subgroups, and similarly for slope over

time. The test of equality of slopes between subgroups

was conducted as a t test within this ANOVA model.

The ANOVA model was fitted to lesion sizes as

reported and also to log-transformed lesion sizes. As

neither model provided a clearly superior fit to the

data, results are reported from the model without

log transformation.

RESULTSOnly one patient had residual enhancing tumor after

the initial rRFA at 1-month follow-up; all other le-

sions showed no enhancement on the first post-treat-

ment scan. In this case, a repeat ablation was performed

approximately 3 months after the initial procedure.

Three lesions demonstrated recurrence (range, 9.7-

28.6 months post-ablation), 2 were treated by repeat

ablations, and 1 was treated by partial nephrectomy.

The initial sizes of these lesions were 6.3 cm, 3.5 cm,

and 3.3 cm (mean, 4.4 cm). As of last follow-up, there

was no secondary recurrence after reintervention.

Patients who had lesions ≥3 cm were significantly

older (mean age, 76±10 vs 65±13, P<.005). There

were no significant differences in glomerular filtra-

tion rate (P=.74), serum creatinine (P=.44), number

of prior interventions (P=.61), gender (P=.15), eth-

nicity (P=.49), or a history of diabetes, hypertension,

and other diseases (P=.97) between the two groups.

There was also no significant difference in lesion lo-

cation (P=.49), kidney side affected (P=.34), and

type of probe used during ablation (P=.58). Lesions

≥3 cm were treated with larger probes (chi-square

test, P<.005) and ablated for longer periods of time

(mean time, 25+10 vs 16+6 minutes, P<.005) than

lesions <3 cm. Although KM survival curves (Figure

1) showed trends toward worse primary recurrence


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(P=.13, Figure 2A) and overall survival (P=.27, Figure

2B) in larger lesions, these trends were not statistically

significant.

Serial changes in lesion size after ablation were mod-

eled as a function of time. The rate of change over time

in lesion size following rRFA did not differ significant-

ly either by initial lesion size (<3 cm vs ≥3 cm, P=.65;

Figure 3A), or between biopsy-proven and non-biop-

sy-proven RCC (P=0.46; Figure 3B). The regression

line for the <3 cm group was lesion size (cm)=2.2139

cm–0.02208 cm×(number of months). For the ≥3 cm

group, the regression line was lesion size (cm)=3.6034

cm–0.01683 cm×(number of months). These models

thus estimate a reduction in treated lesion size (maxi-

mal diameter) over the course of 3 months by 0.066

cm in the <3 cm group, and by 0.050 cm in the ≥3

cm group. Over 12 months, estimated reductions in

treated lesion size are 0.265 cm in the <3 cm group

Figure1. Examples of successful and recurrent masses after rRFA. Successful RFA of a small renal tumor is shown in Figures 1A through 1C. Post contrast renal MRI shows a 2.5 cm solid interpolar left renal mass (A, arrow). RFA was performed with a 3 cm LeVeen electrode positioned centrally within the lesion (B, arrowhead). A follow-up CT performed 8 months later shows successful ablation with no residual tumor enhancement (C, asterisk). The le-sion is now smaller, measuring 2.0 cm in greatest dimension. Recurrence after RFA of a large renal tumor is shown in Figures 1D through 1G. A CT scan shows a 3.3 cm exophytic right renal mass (D, arrow). Ablation was performed with a 3.5 cm LeVeen electrode positioned deep (E, asterisk) and centrally (F, asterisk) within the mass. The patient initially did well, but a follow-up CT scan performed 29 months after the procedure (G) shows focal recurrence (ar-rowhead). The patient subsequently underwent partial nephrectomy.


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Figure 3. Rate of change in lesion size over time post renal radiofrequency ablation treatment. There was no significant difference in serial change in lesion size re-gardless of initial lesion size or biopsy status of lesion.

Figure 2. Kaplan-Meier survival curve of primary recurrence and overall survival. There was no significant difference in primary recurrence or overall survival between patients with lesions ≥3 cm and those with lesions <3 cm.

and 0.202 cm in the ≥3 cm group.

The pooled intercept and slope for the entire

population based on equal weighting over the 2

groups yielded the following regression line: lesion

size (cm)=2.9087 cm–0.01946 cm×(number of

months). This model thus estimates a reduction of

0.058 cm in treated lesion size over the course of 3

months and 0.233 cm over 12 months.

The regression line for the lesions that were not

biopsy-proven RCC was lesion size (cm)=3.236

cm–0.01547 cm×(number of months). For biop-

sy-proven RCC, the regression line was lesion size

(cm)=2.6276 cm–0.02376 cm×(number of months).

These models thus estimate a reduction in treated

lesion size (maximal diameter) over the course of

3 months by 0.046 cm in the non-biopsy-proven

group, and by 0.071 cm in the biopsy-proven group.

Over 12 months, estimated reductions in treated le-

sion size are 0.186 cm in the non-biopsy-proven

group and 0.285 cm in the biopsy-proven group.

0

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2

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0 10 20 30 40 50 60 70

Lesion

Size (cm)

Time (months)

Linear Regression -‐ Serial Change in Lesion Size

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2

3

4

5

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0 10 20 30 40 50 60 70

Lesion

Size (cm)

Time (months)

Linear Regression -‐ Serial Change in Lesion Size

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TABLE 1. PATIENT CHARACTERISTICS

All <3 cm ≥3 cm P value

n 37 20 19

Glomerular filtration rate*

≥60 21 (57) 12 (60) 9 (47) P=.7446

<60 17 (46) 8 (40) 9 (47) Fisher exact test

Serum creatinine**

≥1.5 8 (22) 3 (15) 5 (26) P=.4381

<1.5 30 (81) 17 (85) 13 (68) Fisher exact test

Prior interventions‡

Yes 4 (11) 3 (15) 1 (5) P=.6050

No 33 (89) 17 (85) 18 (95) Fisher exact test

Gender

Male 27 (73) 12 (60) 16 (84) P=.1552

Female 10 (27) 8 (40) 3 (16) Fisher exact test

Ethnicity

White 22 (59) 12 (60) 11 (58) P=.4900

Black 2 (5) 0 (0) 2 (11) Chi-squared test

Asian 4 (11) 2 (10) 2 (11)

Hispanic 9 (24) 6 (30) 4 (21)

Mean age (with SD) 70±13 65±13 76±10 P=.0039Student t-test

Diabetes 12 (32) 5 (25) 7

(37) P=.9732

Hypertension 25 (68) 12 (60) 15 (79) Chi-square test

Other history 17 (46) 7 (35) 10 (53)

*Missing glomerular filtration rate data for 1 patient in ≥3 cm group; 1 patient with 2 lesions <3 cm only ac-counted for one in <3 cm group.**Missing serum creatinine info for 1 patient in ≥3 cm group; 1 patient with 2 lesions <3 cm only accounted for one in <3 cm group.‡Type of intervention: partial nephrectomy of contralateral kidney.


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TABLE 2. LESION CHARACTERISTICS


n 40 21 19

Mean size (cm, with SD) 2.9±1.1 2.1±0.4 3.8±1.0 P<.0001

Image/biopsy-proven renal cell carcinoma #(%)

19 (48) 9 (43) 10 (53)

Clear cell 7 (37) 4 (44) 3 (30)

Papillary 6 (32) 3 (33) 3 (30)

Chromophobe 2 (11) 1 (11) 1 (10)

Mixed 2 (11) 0 (0) 1 (10)

Not specified 3 (16) 1 (11) 2 (20)

Location

Cortical or exophytic 38 (95) 19 (90) 19 (100) P=.4885

Parapelvic 2 (5) 2 (10) 0 (0) Fisher exact test

Side

Right 23 (58) 14 (67) 9 (47) P=.3375

Left 17 (43) 7 (33) 10 (53) Fisher exact test

TABLE 3. TREATMENT CHARACTERISTICS


Probe size (cm)

2.5 1 (3) 1 (5) 0 (0) P=.0026

3 17 (43) 14 (67) 3 (16) Chi-square test

3.5 14 (35) 6 (29) 8 (42)

4 7 (18) 0 (0) 7 (37)

5 1 (3) 0 (0) 1 (5)

Type of probe

LeVeen (Boston Scientific) 32 (80) 18 (86) 14 (74) P=.4420

Cool-Tip (Coviden) 8 (20) 3 (14) 5 (26) Fisher exact test

Mean # lesions treated (with SD) 1±0 1±0 1±0

Mean time of ablation (min) 21±10 16±6 25±10 P=.0020Student t-test


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TABLE 4: PUBLISHED RESULTS OF STUDIES COMPARING CRYOABLATION TO RADIOFREQUENCY ABLATION OF THE KIDNEY.

# Cases (# Patients)

Recurrence # (%)

Complication Success Conclusion

Atwell et al 2013

Cryoablation (CA): 189 (163)Radiofrequency ablation (RFA): 256 (222)

CA: 4 (2.1%) mean 0.9 years post treatmentRFA: 7 (2.7%) mean 2.8 years post treatment

CA: 4.5%RFA: 4.3%

CA: 97.3%, 90.6%, 90.6%RFA: 100%, 98.1%, 98.1%(1-, 3-, and 5-year local recurrence-free survival respec-tively)

CA and RFA can effectively treat renal masses <3 cm.

El Dib et al 2012CA: 500 (457)RFA: 507 (426)

N/ACA: 19.9%RFA: 19.0%

CA: 89%RFA: 90%(clinical efficacy)

CA and RFA can effectively treat renal tumors <4 cm.

Pirasteh et al 2011

CA: 70RFA: 41

CA: 7%RFA: 11%Both 10 months post treatment

CA: 1.4%RFA: 2.4%

N/ACA and RFA result in similar outcomes.


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TABLE 5. PUBLISHED RESULTS OF STUDIES COMPARING THERMAL ABLATIVE PROCEDURES (CRYOABLATION AND RADIOFREQUENCY ABLATION) TO SURGICAL PROCEDURES (PARTIAL NEPHRECTOMY AND RADICAL NEPHRECTOMY).

# Cases (# Patients)

Recurrence # (%) Complication Success Conclusion

Olweny et al 2012PN*: 37RFA: 37

PN: (5.4%)RFA: (8.3%) N/A

PN: 100%, 100%, 89.2%, 94.6%, 91.8%RFA: 97.2%, 97.2%, 89.2%, 91.7%, 97.2%(5-year OS, CSS, DFS, local RFS, MFS respectively)

RFA is an effective mini-mally invasive procedure in treating renal cell carcinoma.

Takaki et al 2010

PN: 10RN: 54RFA: 51

PN: 1 (10.0%)RN: 2 (3.7%)RFA: 1 (2.0%)[Distant Recur-rence]

PN: 10.0%RN: 7.4%RFA: 5.0%

PN: 100%RN: 100%RFA: 82.4% (Prima-ry), 100% (Second-ary)

Although RN and PN had higher OS than RFA, RCC-related survival and DFS were comparable between the 3 treatment methods.

Turna et al 2009

PN: 36 (36)CA: 36 (36)RFA: 29 (29)

PN: 2 (5.6%)‡CA: 6 (16.7%)RFA: 11 (37.9%)

PN: 26CA: 7RFA: 2

PN: 100%, 91%, 100%CA: 88.5%, 88.5%, 69.6%RFA: 83.9%, 83.9%, 33.2%(CSS, OS, DFS respectively)

Although PN provided the best oncological outcome, it had a higher complication rate and worse renal function results.

Lucas et al 2008

PN: 85RN: 71RFA: 86

PN: 2RN: 0RFA: 6

N/A N/ARFA provides similar on-cological outcomes while preserving renal function.

*CA: cryoablation, CSS: cancer-specific survival, DFS: disease-free survival, MFS: metastasis-free survival, OS: overall survival, PN: partial nephrectomy; RFA: radiofrequency ablation, RFS: recurrence-free survival, RN: radical nephrectomy.‡Positive surgical margins reported for partial nephrectomy.


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TABLE 6. PUBLISHED RESULTS OF RENAL RADIOFREQUENCY ABLATION STUDIES (2003-2013).

# Cases (Patients)

Follow-Up (Months)

Tumor Diam-eter (cm) Complication Technical

Success Conclusion

Atwell et al 2013 256 (222) — Mean: 1.9±0.5

Median: 1.8 4.3% 99.6%

5-year local RFS* rate for RFA: 93.2% (overall); based on location, 62.3% (central), 97.7% (exophytic), 92.8% (intraparenchymal).

Balageas et al 2013 71 (62) Mean: 38.8

Range: 18-78Median: 2.3(0.8-4.6) 5.9% (P) 95.2%

(S) 98.4%

5-year DFS: 61.9%OS: 90.1% (<3 cm) and 44.0% (>3 cm), P=.03Central location associated with increased risk of complications.

Nitta et al 2012 24 (22) Mean: 18

Range: 1-61Mean: 2.4 (1.0-4.5) 14% — OS: 79%, RFS: 85%

Zagoria et al 2011 48 (41) Median: 56 Median: 2.6 — —

Local RFS: 88%, DFS: 83%, 5-year OS: 66%Authors recommend RFA for RCCs less than 4 cm.

El Dib et al 2011 507 (426)

Mean: 18.1Range: 9.0-30.7

Mean: 2.7(2.0-4.3) 19% 90%

Numbers include laparoscopic renal RFA.CA and RFA are similar in terms of complication rates and technical success.

Ferakis et al 2010 39 (31) Mean: 61.2

Range: 36-84Mean: 3.1 (1.3-7.5) — (P) 90%

(S) 97%Larger tumors have a higher likeli-hood for recurrence.

Takaki et al 2010 51 (51) Mean:

34.0±23.2 Mean: 2.4±0.7 5% (P) 82.4%(S) 100%

5-year OS: 75%, 5-year DFS: 98%Complications were all minor; no major complications reported.

Tracy et al 2010 243 (208) Mean: 27±23

Range: 1.5-90Mean: 2.4±0.8 (1.0-5.4) — 97% 5-year RFS: 93%, 5-year OS: 85%

Hiraoka et al 2009 77 (40) Median: 16

Range: 1-63Median: 2.4 (1.1-5.3) 3.9% 85%

Complications were all minor; no major complications reported.

Levinson et al 2008 34 (31)

Mean: 61.6Median: 62.4Range: 41-80

Mean: 2.1 (1.0-4.0) 20.6% 91.2%

Most reported complications were minor.DSS: 100%, MFS: 100%, RFS: 89.2%OS: 62.7% (all at 80 months)

Zagoria et al 2007 125 (104) Mean: 13.8 Mean: 2.7 (0.6-

8.8) 8% (P) 87.2%(S) 93%

Tumor-free survival: 100% (<3.6 cm), 47% (>3.7)Each cm 1 increase in diameter over 3.6 cm decreases tumor-free survival by a factor of 2.19.

Gervais et al 2003 42 (34) Mean: 13.2

Median: 9.9Mean: 3.2 (1.1-8.9) 7.4% 86%

Success based on size; small: 100%, large: 73%Centrally located renal masses up to a size of 5 cm can be successfully treated by RFA.

*P: primary, S: secondary, CA: cryoablation, CSS: cancer-specific survival, DFS: disease-free survival, MFS: metastasis-free survival, OS: overall survival, RFA: radiofrequency ablation, RFS: recurrence-free survival.


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Results for the pooled intercept and slope for the en-

tire population based on equally weighting over these

2 groups were very similar to the intercept and slope

pooled over the <3 cm group and the ≥3 cm group.

Two out of 3 recurrent lesions were biopsy-proven

papillary RCC. Whether or not a lesion was biopsy-

proven RCC was not a significant factor in determin-

ing primary recurrence (Fisher exact test, P=.33).

Complications

Eight out of 37 total patients experienced compli-

cations after rRFA. The severity of the complications

was determined using the Society of Interventional

Radiology (SIR) Clinical Practice Guidelines.16 In

our study, minor complications included hemorrhage

that did not require a blood transfusion (1), mild

perinephric hematoma (2), flank pain (3), postproce-

dure urinary tract infection (1), hydronephrosis (2),

gastroenteritis (1), and diarrhea (1). Major complica-

tions included thermal injury to an intercostal nerve

(1), chronic hematuria (1), renal insufficiency (1), and

colon injury (1). The patient with colon injury had a

posteriorly positioned splenic flexure that sustained

thermal injury during rRFA despite CT evidence of

a sufficient fat plane between the RFA probes and

the colon; this patient underwent colonic resection.

There were no other major unplanned procedures

following rRFA.

DISCUSSIONThermal ablation techniques including RFA and

cryoablation (CA) have demonstrated efficacy in

treating renal tumors. A recent review of published se-

ries studied 385 patients with 445 renal masses—all

measuring ≤3.0 cm—treated by either RFA (n=256

tumors in 222 patients) or CA (n=189 tumors in 163

patients).17 At a mean follow-up of 2.8 years, 7 cas-

es of recurrence and a 4.3% complication rate were

found for RFA. Following cryoablation, 4 cases of re-

currence (mean, 0.9 years after treatment) and 4.5%

complication rate were observed. There were no sig-

nificant differences between RFA and CA for techni-

cal success, complication rates, and recurrence rates.

The authors, however, recommended cryoablation for

large lesions due to the ability of cryophobes to create

large ice balls of up to 8 cm. They noted that cryo-

ablation may be preferential for centrally located le-

sions due to published results that described failures,

limitations, and incomplete ablations associated with

central lesions treated by RFA.18-20 The size of cryo-

ablated lesions may also decrease to a greater degree

and at a faster rate than those treated by RFA.21 In

another series comparing CA (n=600 cases) to RFA

(n=775 cases), RFA-treated lesions had significantly

higher rates of local tumor progression and a greater

tendency toward metastatic progression.22 Neverthe-

less, most studies indicate similar clinical outcomes for

RFA and CA (Table 4).17,21,23-24

A comparison of RFA and partial nephrectomy has

resulted in mixed findings (Table 5). In one study of

renal tumors in solitary kidneys, RFA had lower mor-

bidity and complication rates than laparoscopic partial

nephrectomy.25 Another study found no significant

difference between the two methods for 5-year dis-

ease-free survival probability, local recurrence-free sur-

vival probability, and metastasis-free survival probabil-

ity.26 Although patients with independent risk factors


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associated with increased recurrence were excluded

in this study, others argue that the outcomes of RFA

and partial nephrectomy cannot be directly compared

because of selection bias.6,27,28 For example, current

partial nephrectomy patients tend to be younger with

fewer comorbidities, contributing to increased overall

survival rates.6,28

Our report compares favorably to prior studies that

have demonstrated high technical success rates and

low complication rates for rRFA (Table 6). Similar to

prior results, we found a higher rate of primary recur-

rence for lesions ≥3 cm in maximal diameter. In fact,

there was no recurrence for smaller tumors. However,

the absolute rate of recurrence was still very low for

tumors ≥3 cm (3 out of 19 treated lesions [16%]). After

recurrent tumors were treated by repeat rRFA, there

was no difference in secondary recurrence or need for

additional therapy between the 2 groups. Notably, pa-

tients with larger lesions can still be successfully treat-

ed by RFA, although a second ablation may be nec-

essary in some patients. Many studies similarly show

high secondary success rates after repeat ablation.6,12,29

Thus, tumor size alone should not be considered a

contraindication to rRFA as long as close surveillance

is performed to allow repeat ablation if needed.

Overall complications were noted in 8 out of 37 pa-

tients (22%). Four patients (11%) experienced major

complications requiring either an unplanned hospital

admission or an unplanned increase in patient care.

Four patients (11%) experienced minor complications

that did not require extra patient care, hospital stay, or

intervention. One patient with a pre-existing history

of CKD started dialysis 39 months after treatment. No

other patients started dialysis after rRFA treatment,

confirming the safety of the procedure in preserving

viable renal mass.

Gervais et al18 noted that 6 months after ablation, 20

out of 23 tumors decreased in size only slightly by 1

cm or less; the remaining 3 tumors decreased by more

than 1 cm.30 To our knowledge, no prior work has de-

scribed serial changes to lesion size following RFA in-

tervention in detail. Therefore, we tracked lesion size

at each follow-up appointment after the initial pro-

cedure. A linear regression model illustrated that the

decline in lesion size after rRFA was similar despite

the baseline diameter of the treated lesion. Another

linear regression analysis showed post-rRFA reduc-

tion in size was preserved regardless of whether or not

the lesion was a biopsy-proven RCC. In our series,

recurrent tumors increased in size with new contrast

enhancement in follow-up images. Familiarity with

the anticipated temporal course in lesion size may be

important in early assessment of recurrence, particu-

larly in patients unable to receive iodinated contrast

for CT scans.

CONCLUSIONRenal radiofrequency ablation safely and effec-

tively treats kidney tumors, including RCC. Com-

plication and recurrence rates are more common

in lesions ≥3 cm, but major complications remain

low. A repeat ablation may be necessary in a small

percentage of patients with larger lesions. In this

group, a lack of subsequent recurrence suggests

that size alone should not be considered a con-

traindication to rRFA treatment. After ablation,


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serial changes in lesion size are similar regardless

of the original size and regardless of whether the

lesion had been biopsy-proven RCC.

ACKNOWLEDGEMENTSThe authors would like to thank Yitzchak David,

MPH, for providing the statistical analysis of the data,

and David Daniel for his assistance in researching ref-

erence materials.

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Disclosure: The authors have completed and re-turned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no disclo-sures related to the content of this manuscript.Manuscript received February 16, 2014; provision-al acceptance given March 18, 2014; final version accepted March 25, 2014.

Address for correspondence: John H. Rundback, MD, 718 Teaneck Road, Teaneck, New Jersey 07666, United States. Email: [email protected] name.org

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