A matched-cohort comparison of laparoscopic cryoablation and laparoscopic partial nephrectomy for treating renal masses

Authors


Samir S. Taneja, Department of Urology, New York University Urology Associates, 150 East 32nd Street, 2nd Floor, Suite 200, New York, NY 10016, USA.
e-mail: Samir.Taneja@nyumc.org

Abstract

OBJECTIVE

To compare the surgical outcomes of elderly patients with renal masses treated with laparoscopic partial nephrectomy (LPN) or laparoscopic cryoablation (LCA).

PATIENTS AND METHODS

All 15 patients who had LCA at the authors’ institution between May 2003 and July 2005 were included, and compared with a matched cohort of 15 patients selected by patient age and tumour size, from a pre-existing database of 104 patients who had LPN from July 2002 to July 2005. The two groups were compared for gender, number of comorbidities, American Society of Anesthesiologists status (ASA), body mass index (BMI), baseline renal function and haematocrit, location and size of lesion, length of stay, operative time, estimated blood loss (EBL), transfusion rate, number and type of complications, conversion rate, and postoperative renal function and haematocrit.

RESULTS

The two groups were similar in age, sex, BMI, ASA, baseline renal function, haematocrit, size and side of tumour, the percentage of exophytic tumours, and the likelihood of more than one comorbidity. Surgical outcomes between the groups were also relatively similar. The length of stay, creatinine and haematocrit levels after surgery did not differ between the groups. The LPN group had a significantly longer operation (248 vs 152 min, P < 0.001) and higher EBL (222 vs 59 mL, P = 0.007) than the LCA group, but only one patient required a transfusion and there was no discernible difference in discharge haematocrit values. No recurrences were detected in either group, with a similar mean follow-up of 9.8 and 11.9 months, respectively.

CONCLUSION

Although this matched-cohort comparison showed that LPN had a higher mean EBL, a longer operation and higher relative risk of open conversion, the overall clinical outcome was similar in terms of complication rates, length of stay and changes in creatinine and haematocrit after surgery. In this small retrospective evaluation, there was similar morbidity, treatment outcome and short-term efficacy with LCA and LPN. At present, although still experimental, LCA is a good choice for elderly patients with comorbidities precluding blood loss or renal ischaemia. However, in experienced hands, LPN is a preferred option for most elderly patients and should be considered when contemplating definitive treatment of renal masses.

Abbreviations
LPN

laparoscopic partial nephrectomy

LCA

laparoscopic cryoablation

ASA

American Society of Anesthesiologists

BMI

body mass index

EBL

estimated blood loss

US

ultrasonography.

INTRODUCTION

The incidence of RCC has steadily increased in the last 30 years, probably because of the technological advances made in noninvasive imaging [1,2], with consequent decreases in renal tumour size and stage at diagnosis. However, the age at diagnosis has remained relatively unchanged [1,3], resulting in a growing population of patients in the sixth or seventh decades of life with small, localized renal tumours. Advances in minimally invasive techniques now allow urologists several options for definitively treating small renal masses in this population, but the indications for each are currently poorly defined.

Laparoscopic partial nephrectomy (LPN) is used progressively more often for treating patients with small (<4 cm) peripheral tumours, but it is a complicated procedure requiring laparoscopic surgical expertise. Its use in elderly surgical candidates with known comorbid conditions is controversial. Ablative therapies for small, peripheral renal lesions have become more popular due to the demonstrated success in animal models and the minimal morbidity associated with the procedure [4]. Cryoablation is the oldest and most studied of the ablative therapies [5] although its use in the treatment of renal tumours is still preliminary, with relatively few long-term outcomes reported. Laparoscopic cryoablation (LCA) has been used mostly in elderly patients who are considered poor surgical candidates; it has been assumed that ablative treatments are less morbid for the patient and are therefore more likely to result in better outcomes than LPN. The goal of the present study was to compare the surgical outcome in elderly patients with known comorbities treated with either LPN or LCA.

PATIENTS AND METHODS

All 15 patients who had LCA at the authors’ institution between May 2003 and July 2005 were selected for inclusion in the study; a matched group of 15 patients was selected based on patient age and tumour size, from a pre-existing database of 104 patients who had LPN from July 2002, to July 2005.

After obtaining approval of the protocol by the by the local Institutional Review Board, the patients’ charts were retrospectively reviewed for gender, number of comorbidities, American Society of Anesthesiologists status (ASA), body mass index (BMI), baseline renal function and haematocrit, location and size of lesion, length of stay, operative time, estimated blood loss (EBL), transfusion rate, number and type of complications, conversion rate, and renal function and haematocrit after surgery. The results were analysed statistically using a two-tailed Student’s t-test for continuous variables and the Pearson chi-squared test for categorical data.

All LCA procedures were performed by one surgeon (M.S.), and all LPN procedures by one of two surgeons (M.S. and S.T.). LCA was performed using the Seed Net&ãgr; system (Oncura, Plymouth Meeting, PA, USA). The technique included laparoscopic renal exposure, tumour location using intraoperative ultrasonography (US), and tumour exposure through mobilizing perinephric fat. A double freeze-thaw cycle was used in all cases, with cryoablative needle probes, under laparoscopic US guidance, resulting in an ice-ball ≈ 1 cm beyond the margins of the mass. The follow-up included a history and physical examination, chest X-ray and contrast-enhanced renal CT at 3, 6, 12 and 18 months.

LPN was performed by laparoscopic tumour exposure followed by intraoperative US-guided tumour excision. Temporary renal vascular occlusion was used in all cases with i.v. mannitol administration before and immediately after renal ischaemia. The lesion was excised using sharp dissection under direct vision, with sampling of the defect to confirm negative margins. Haemostasis was achieved using a combination of electrocoagulation, intracorporeal suturing, and application of tissue adhesives. The technique used depended on the depth of resection, presence of collecting system injury, and surgeon preference. The follow-up included a history and physical examination, and chest X-ray at 3, 6, 12 and 18 months.

RESULTS

The characteristics of the two groups of patients are shown in Table 1. The two groups were similar in age, sex, BMI, ASA, baseline renal function, haematocrit, size and side of tumour, the percentage of exophytic tumours, and the likelihood of more than one comorbidity (Table 1).

Table 1.  The patient and tumour characteristics, and the surgical outcome, of the two groups
CharacteristicLPNLCAP
  • *

    significant. N/A, not applicable.

Number of patients 15 15 
Study period 07/2002–07/2005 05/2003–07/2005 
Mean (sd) age, years 75.7 (4.6) 76.1 (4.5)0.812
% male 79 570.491
% solitary kidney  0 14N/A
% ASA 3 or 4 53 620.780
Mean (sd) BMI, kg/m2 27.1 (3.9) 29.1 (6.8)0.309
% >1 comorbidity 47 471.000
Mean (sd):
 preop. creatinine, mg/dL  1.21 (0.16)  1.17 (0.33)0.681
 preop. haematocrit, % 40.7 (3.5) 38.4 (3.2)0.068
 tumour size, cm  2.5 (1.0)  2.7 (1.3)0.524
% left-sided 60 430.487
% exophytic 85 570.371
Outcome measure
Complications  2 major, 1 minor  2 major, 2 minorN/A
Mean (sd):
 length of stay, days  4.4 (3.9)  3.3 (3.3)0.412
 operative duration, min248.4 (60.1)152.2 (37.3)<0.001*
 ablation time, min 15.3 (3.4)N/A
 ischaemic time, min 27.6 (6.0)N/A
 EBL, mL221.7 (182.5) 58.7 (28.5)0.002*
 postop. creatinine, mg/dL  1.18 (0.24)  1.19 (0.29)0.891
 postop. haematocrit, % 34.6 (4.1) 35.1 (3.9)0.766
Transfusions  1  0N/A
Follow-up, months  9.83 (8.8)  11.9 (7.2)0.563
% Conversion 13  0N/A
Recurrences  0  0N/A

The surgical outcome of the two groups were relatively similar (Table 1); the length of stay, creatinine and haematocrit values after surgery did not differ between the groups. In the LCA cohort there were two major complications, including pneumonia and myocardial infarction, and two minor complications, including a gout attack and hyponatraemia with confusion. In the LPN group there were two major complications in the same patient, i.e. a myocardial infarction and deep venous thrombosis. This patient was also the only one to undergo open conversion of a planned LPN. One other patient had conversion of a LPN to a laparoscopic radical nephrectomy. The only transfusion required was in the LPN group and was thought to be due to a self-contained perirenal haematoma (minor complication). The major complications caused a longer stay in both groups, but did not require operative interventions.

The LPN group had a significantly longer operation (248 vs 152 min, P < 0.001) and higher EBL (222 vs 59 mL, P = 0.007) than the LCA group, but as noted, only one patient required a transfusion and there was no discernible difference in discharge haematocrit levels. No recurrences were detected in either the LPN or LCA groups, with a similar mean follow-up of 9.8 and 11.9 months, respectively (Table 1).

DISCUSSION

Advances in diagnostic imaging are allowing the diagnosis of smaller asymptomatic renal masses at earlier stages [3]. Because RCC accounts for most incidentally discovered solid renal masses [2], these masses generally require definitive treatment. Minimizing morbidity and mortality is of utmost importance in approaching these lesions, given the incidental, asymptomatic nature of the tumours, the unknown impact of small renal cancers on longevity, and because a significant number of these lesions will be benign. Although open PN has been the reference standard for nephron-sparing surgery, recent reports of the outcome of LPN showed excellent surgical results and cancer control when used to treat small (<4 cm) peripheral tumours [6–10]. Because laparoscopic techniques decrease operative morbidity, length of stay, time of convalescence and the use of medication for pain [7,9], LPN is emerging as a standard option for treating patients with a low operative risk.

Cryoablation is the oldest and most studied of the ablative techniques, although renal cryoablation was not described until the 1990s [5]. LCA has distinct advantages over the percutaneous approach, including the ability to precisely confirm the probe position and define tumour extent with intraoperative US [11]. Cryoablation has been used experimentally by several centres, but long-term data on surgical outcomes and cancer control are still pending. The longest follow-up was documented by Gill et al.[12] at the Cleveland clinic, and the data show promising results. At 3 years of follow-up the mean percentage reduction in tumour size was 75%, with 38% of tumours being undetectable on MRI. At the 6-month follow-up 0.5% of those undergoing CT-guided biopsy had recurrence of RCC, and these were successfully treated with laparoscopic radical nephrectomy. The 3-year cancer-specific survival for the 51 patients studied with unilateral sporadic renal tumour was 98%, and the overall survival was 89%.

Gill et al.[11,12], and others, recognizing that LCA is a technique requiring further clinical validation, used it in elderly patients who are a poor surgical risk and who have small enhancing tumours. It is thought that the morbidity and mortality of other nephron-sparing techniques in this population would be prohibitive. Desai and Gill [8] retrospectively compared all patients with ≤ 3 cm peripheral enhancing tumours who had LPN at the Cleveland Clinic from 1997 to 2003, with those who had LCA. They found the two groups to have a similar operative duration, length of stay, total convalescence, and percentage increase in creatinine level. The LPN group was significantly different from the LCA group in that they were younger, had a lower ASA status, lower baseline creatinine levels and larger tumours. Complications after surgery and the EBL were also significantly higher in this group. The authors noted that the baseline differences in the two groups were to be expected, and reflected the differing indications for using LPN vs LCA, which were at the discretion of the one operating surgeon. The surgeon tended to offer LCA to patients who were older, had smaller tumours (<3 cm), baseline renal insufficiency and who were considered to be poor operative risks.

It was the aim of the present study to investigate whether these indications are appropriate, by examining the surgical outcomes of a group of patients treated by LPN and matched by age and size of lesion with the group who had LCA at our medical centre. The two groups were similar in baseline characteristics, including age, ASA status, number of comorbities, baseline creatinine level and size of tumour. Although the matched-cohort comparison showed that LPN had a higher mean EBL, a longer operation and higher relative risk of open conversion, the overall clinical outcomes were similar in complication rates, length of stay, and changes in creatinine and haematocrit levels after surgery.

We agree that LPN requires advanced laparoscopic skills, such as intracorporeal suturing for repairing collecting system injury and, as a result, might incur a higher risk than LCA. However, we think that in expert hands the differences in surgical outcome can be minimal and clinically insignificant, even in elderly patients with multiple comorbidities. We think that the likelihood of complications and open conversion decrease progressively with operator experience (as has ours since compiling the present data). LPN offers clear advantages over LCA, which in our opinion support incurring the additional risk of morbidity in carefully selected patients.

LPN allows accurate diagnosis and staging of renal malignancies, and avoids the sampling error associated with biopsy. The follow-up of lesions that have been ablated is also necessarily more rigorous and less cost-effective because the tumour remains in situ. Long-term cancer outcomes of patients treated with LCA are as yet unknown. For all of these reasons, we advocate LPN over LCA for treating small renal masses in most patients. We think that LCA has a limited role in selected individuals with significant comorbidities precluding potential blood loss, impaired baseline renal function precluding renal ischaemia, and/or centrally located tumours requiring complex renal reconstruction.

We recognize the limitations of the present study, including the small groups, retrospective design and inherent selection bias in a matched-group design, but we feel that the results support our current practice and show that the indications for LCA are still in question. A long-term investigation of larger groups and possible prospective analysis will confirm the appropriate indications for LCA and the effectiveness of its cancer control.

In conclusion, the increasing frequency of the detection of renal masses in the ageing population, with the high likelihood of malignancy in such masses, demands a definitive strategy for effectively treating small renal masses. The desire to effectively treat must be balanced with minimizing morbidity, given the incidental, asymptomatic nature of the tumours, the unknown impact of small renal cancers on longevity, and because many of these lesions will be benign. In the present small retrospective evaluation, we showed that morbidity, treatment outcome and short-term efficacy are similar with LCA and LPN. At present, although still experimental, LCA is a good choice for elderly patients with comorbidities precluding blood loss or renal ischaemia. However, in experienced hands, LPN is a preferred option for most elderly patients and should be considered when contemplating the definitive treatment of renal masses.

CONFLICT OF INTEREST

None declared.

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