Can RENAL and PADUA Nephrometry Indices Predict Complications of Laparoscopic Cryoablation for Clinical Stage T1 Renal Tumors?

Abstract

Objective:

Assessment of anatomical complexity with the RENAL (radius; exophytic/endophytic; nearness; anterior/posterior; location) and preoperative aspects and dimensions used for anatomical classification (PADUA) nephrometry indices is used to predict complications related to surgical extirpation treatment for patients with clinical T1a/b renal mass. This single center study aims to investigate the value of these indices to predict complications in a cohort of patients treated with laparoscopic cryoablation (LCA) for cT1 renal mass.

Materials and Methods:

Single institution data from consecutive LCA procedures were prospectively collected from December 2006 to April 2013. Renal mass anatomical complexity was categorized according to RENAL and PADUA indices. Comorbidity was assessed by the Charlson-index. Intraoperative complications (IOCs) were reviewed and categorized: blood loss >100 mL, conversion, tumor fracture, and incomplete ablation. Postoperative complications (POCs) were graded using the modified Clavien-index. Univariate and multivariate logistic regression models addressed the risk for complications.

Results:

Ninety-nine LCA procedures were included. The median RENAL-score was 7.0 (standard deviation [SD] 1.7), and the median PADUA-score was 8.0 (SD 1.6). IOC occurred in 19 procedures (19%). The risk for IOC was significantly correlated (p<0.05) with tumor diameter (mm), surface, volume, the RENAL domains “R-size,” “N-nearness to collecting system,” “RENAL score,” and the PADUA domain “diameter.” In multivariate analysis with surgical complication as the independent variable, tumor diameter, surface, and volume were determining factors. A threshold was set for 35 mm tumor diameter, it being predictive for an increased risk for IOC performing LCA. Twenty-three POC occurred in 20 patients. On univariate analysis, the RENAL domain “nearness to collecting system,” and no PADUA domains, had a significant association with POC.

Conclusion:

The RENAL score, and not the PADUA score, is associated with a higher risk for IOC. A noncategorized method of scoring tumor diameter showed a more significant correlation with the risk for IOC than the categorized method of the nephrometry indices. As a result a threshold diameter of 35 mm was established.

Introduction

Principal guidelines advise that treatment methods for small renal masses must aim to preserve renal function and provide oncologic control.^1,2 Partial nephrectomy (PN) is considered a therapeutic standard for the conduct of clinical T1 renal masses. Currently, in selected cases, the thermal ablative modality of cryoablation (CA) is regarded as an alternative treatment option to PN or radical nephrectomy (RN).

Anatomic classification systems (ACS) such as the preoperative aspects and dimensions used for anatomical classification (PADUA) and RENAL (radius; exophytic/endophytic; nearness; anterior/posterior; location) nephrometry indices, were originally designed to aid in the decision-making process to best determine which type of surgery, PN or RN is most desirable.^3,4 However, in the case of a clinical stage T1 renal mass, it would be most convenient if nephrometry indices can be used to provide advice for extirpative and for ablative therapy.

Today, minimally invasive surgical techniques for the treatment of small renal masses reduce hospital stays and treatment-related morbidity, thus permitting the rapid return to everyday life.^1,2 Laparoscopic or robotic PN requires high-level surgical skills and has a challenging learning curve.⁵ However, in experienced hands, the complication rate of laparoscopic or robotic PN is equivalent to that of open PN.⁶ Clearly, the preference for a particular surgical technique can be influenced by its accompanying complication rate. Despite selection bias, radiofrequency ablation (RFA) and CA are recognized for their lower complication rates compared to PN.^1,2,7 Therefore, principal guidelines regarding RFA and CA as alternative treatment options are needed especially for high-surgical risk patients desiring active treatment.

Several study groups investigated the predictive value of the PADUA and RENAL nephrometry indices for the risk of complications in extirpative surgery.^3,8
–10 Hence, if the standardization of renal mass anatomical complexity and its correlation with risk for complications is considered as relevant in extirpative surgery, then this should ideally also apply to ablative therapies. Currently, series of renal masses treated with percutaneous image guided or laparoscopic CA or RFA have studied the relation between anatomical complexity using the RENAL nephrometry score and the risk of complications.^11

–15 No such studies have been performed using the PADUA index.

To date, patients selected for laparoscopic cryoablation (LCA) are informed about the risk for complication based on the surgeon's experience and intelligence gathered from published series. We emphasize that a standardized scoring system for the complexity of renal mass is desired when the benefits and risks, including oncological and renal functional outcome, and possible morbidities of nephron-sparing surgical treatments such as PN (open, laparoscopic, and robotic) and ablation modalities (CA and RFA; percutaneous and laparoscopic) are compared.

The principal objective of this study is to evaluate the value of RENAL and PADUA indices for predicting the risk of intraoperative (IOC) and postoperative (POC) complications in a cohort of patients that underwent LCA for a small renal mass. The additional objective of this study is to identify whether tumor upper pole location or medial/hilar location are risk factors for complications of LCA. The final objective of this study is to establish a threshold value for tumor diameter that indicates the sensitivity for the increased risk of IOC performing LCA.

Patients and Methods

Patient characteristics and data collection

In this nonrandomized retrospective cohort study, consecutive cases of primary renal tumors treated with LCA between December 2006 and April 2013 were evaluated. Patients were identified in our institutional database. The local internal review board approved the study design and the submission for publication.

Patient records were examined and data of age, body mass index (BMI), Charlson comorbidity index (CCI),¹⁶ age-adjusted Charlson comorbidity index (a-CCI),¹⁷ pre- and postoperative renal function (glomerular filtration rate–modification of diet in renal disease [GFR-MDRD]), laparoscopic approach, side of surgery, histology, and hospital stay were collected.

The anatomical complexity of each renal mass was determined using tumor size, location, and closeness of the renal mass to the urinary collecting system. These parameters and their categorized equivalents according to the PADUA and RENAL indices for classification of the anatomical complexity of renal masses were examined.^3,4 Intravenous contrast-enhanced coronal and axial computed tomography (CT) scanning or magnetic resonance imaging (MRI) were used to assess each category of these scores. The interpretation of the imaging and the scoring of the anatomical complexity were performed by a single staff urologist. Tumor surface and volume were calculated using the diameter of the tumor in millimeters, assuming round symmetry.

Tumors located at the renal upper pole or at the medial side near to the hilum are considered less accessible for LCA than tumors located lateral and below the upper polar or sinus lines. Therefore, the domain “longitudinal location” of the PADUA nephrometry index and the domain “location relative to the polar line” of the RENAL nephrometry index were analyzed for true upper pole location.

Laparoscopic cryoablation

According to principal guidelines, all patients were informed about optional treatment methods for small renal tumors. Patient, surgeon, or multidisciplinary uro-oncology committee preferences set indication for LCA. All patients consented to LCA. The same surgeon performed all procedures. A retroperitoneal approach was preferred whenever it was considered technically feasible. Tumor location and identification was confirmed with endoscopic ultrasonography (Hitachi Medical Systems, Tokyo, Japan). All renal masses were intraoperatively biopsied before cryoprobe placement. A standard of 3–5 biopsies were performed using a Magnum™ biopsy gun (Bard^®, Covington, LA) loaded with a disposable 16-gauge automatic side-cutting biopsy needle with a sample notch range of 19 mm. For CA, multiple 17-gauge cryoprobes (Galil Medical, Yokneam, Israel) were used. The selection of the number and type of cryoprobes depended on the tumor volume. Temperature probes were used at indication. A standard of two freeze cycles of 10 minutes were performed. After each freeze cycle a passive thaw cycle for ∼6 minutes was initiated and thereafter switched to an active thaw for 2 minutes. The endoscopic ultrasonography was also used for guiding probe placement and monitoring the freeze process. At indication probes are replaced, freeze cycles adjusted, or additional probes are introduced. After completing the CA and the removal of the cryoprobes a compress of collagen sponge (TachoSil^®) was draped over the lesion as a method for hemostasis.

Complication outcomes

IOCs were scored and categorized in technical complication (conversion), blood loss >100 mL, and tumor fracture. Also, an incomplete ablation of the renal tumor accessed at first time postoperative imaging (range 2–14 weeks) was considered as an IOC. It can be argued that incomplete ablation should be considered as an IOC, however, we defined that a clearly incomplete ablation is a technical or procedural failure related to the surgery itself and therefore should be considered as a complication of surgery. POCs, with a minimum of 1-month follow-up were scored according to the modified Clavien complication classification system (CCS). They were graded as minor (CCS: 1–2) or major (CCS: 3–5).¹⁸ For the report of complications, the Martin criteria were followed.¹⁹

Statistical analysis

Data of the reviewed patients were anonymously entered in an anonymous database and analyzed with Statistical Package for Social Sciences software, v.18.0 (IBM Corporation, SPSS Statistics, Armonk, NY). For comparison of continuous variables, the t-test was used. Pearson's correlation coefficient r was used to test the relation of several parameters. Multivariate logistic regression analysis using stepwise selection was used to identify significant predictors of complications, controlling for age and sex. Univariate analysis was used to select variables. A p-value <0.05 was considered as statistically significant.

Results

General results

Patient characteristics and general surgical information of the cohort is demonstrated in Table 1. The median follow-up was 37.7 months (standard deviation [SD] 20.1 months). Two patients underwent a second LCA for a newly developed renal mass or a synchronous renal mass at the contralateral kidney.

Table 1.

Patient and Surgical Characteristics

	n	Mean	Range	SD
Patients	97
Male	67
Female	30
Age (years)		66.4	36–84	10.6
LCA procedures	99
Tumor diameter (mm)	99	29.9	15–50	7.6
Benign histology	15
Malignant histology	84
Preoperative GFR-MDRD (mL/min/1.73 m²)	99	73.0	19–149	23.8
Preoperative GFR-MDRD<60 (mL/min/1.73 m²)	25	43.5	19–59	13.3
Solitary kidney	8
BMI (kg/cm²)	99	27.1	18.7–41	4.7
ASA	50	2.0	1–3	0.5
CCI	99	1.9	0–8	2.0
a-CCI	99	4.0	0–11	2.5
Laparoscopic retroperitoneal approach	52
Laparoscopic transperitoneal approach	47
Right side	55
Left side	44

n=number; SD=standard deviation; GFR-MDRD=glomerular filtration rate–modification of diet in renal disease; ASA=American Society of Anesthesiologists; BMI=body mass index; CCI=Charlson comorbidity index; a-CCI=age-adjusted Charlson comorbidity index; LCA, laparoscopic cryoablation.

Out of the 99 primary tumors that were treated with CA, 84 were histologically diagnosed as malignant (clear cell renal cell carcinoma [RCC] n=54; chromophobe RCC n=12; papillary RCC n=15; undefined carcinoma n=2; and B-cell lymphoma n=1) and 15 were diagnosed benign (oncocytoma n=11; angiomyolipoma n=4). In three patients, the diagnosis was assessed by preoperative image guided biopsies. A biopsy specimen alone is not eligible for studying capsular or perirenal fat invasion, therefore, in 39 procedures, in addition to intraoperative renal mass biopsy, the peritumoral fat tissue covering a renal cancer was sampled for histological examination for staging purposes. None of these 39 specimens showed malignant invasion into the peritumoral fat.

The treatment success of CA is determined at the time of the first postoperative contrast CT-imaging a minimum of 2 weeks after surgery and is defined by the appearance of (focal) enhancement of the ablated tumor area.²⁰ In three procedures, the ablation was found incomplete at first time imaging, which was considered as an IOC. Therefore, the surgical success rate for primary CA assessment was 97%. After initial treatment success, a later focal recurrence at the primary tumor ablation site is most likely to be expected in those cases that revealed RCC. In the group of 84 proven RCC tumors treated by LCA, 3 late recurrences were detected at a consecutive follow-up. The median follow-up of this RCC cohort was 36 months (SD 20.3 months). The three recurrences were successfully retreated with percutaneous CT-guided CA. Three patients, all with proven RCC, died. One patient died of metastasized RCC; one died of metastasized transitional cell carcinoma of the bladder, and one died of metastasized rectal cancer. The overall oncological failure rate in this series of primary LCA for RCC, assessed by the number of incomplete ablation plus the number of later occurred recurrences, was 7.1%.

The mean postoperative hospital stay was 3 days (range 1–12 days). There was no significant difference in hospital stay (p=0.193) among patients who were approached by retroperitoneal or transperitoneal surgery. Within the time frame of 1 month after LCA, one patient was readmitted because of fever due to a perirenal abscess that required intravenous treatment with antibiotics.

The mean preoperative GFR-MDRD was 73.0 mL/min/1.73 m². The postoperative mean GFR-MDRD was 72.2 mL/min/1.73 m². This difference was not significant (p=0.439).

Anatomic classification systems

The renal tumors were classified according to their anatomical complexity. Using the PADUA-index, a the score of low-, intermediate-, and high-grade complexity was assessed for 42 (score 6–7), 38 (score 8–9), and 19 (score ≥10) tumors, respectively, whereas 48 tumors scored low- (score 4–6), 48 intermediate- (score 7–9), and 3 high-grade (score 10–12) complexities using the RENAL-index. As shown in Figure 1, there seems a trend toward increased anatomical complexity using the PADUA-index compared with the RENAL-index. However, this was not significant (p=0.5). The median RENAL-score was 7.0 (SD 1.7), and the median PADUA-score was 8.0 (SD 1.6). In the domain “longitudinal location” of the PADUA-index, 26 tumors were found entirely above the upper sinus line. In the domain “location relative to the polar line” of the RENAL-index, 27 tumors were located entirely above the upper polar line.

FIG. 1.

Distribution patterns of anatomical complexity categories according to the RENAL (radius; exophytic/endophytic; nearness; anterior/posterior; location) and preoperative aspects and dimensions used for anatomical classification (PADUA) indices for the same cohort of renal masses, each treated with laparoscopic cryoablation (n=99).

Complications

A total of 23 IOCs occurred in 19 out of the 99 procedures. The complications for the categories blood loss >100 mL, tumor fracture, incomplete ablation, and conversion were scored 12, 5, 3, and 3 times respectively. In four patients, more than one IOC occurred.

Following the 99 LCA-procedures, in the postoperative period up to 30 days, a total of 23 complications occurred in 20 patients. Two major complications (CCS: 3a) were scored. In this case, a subphrenic infected hematoma was drained under local anesthesia and using ultrasound guidance. Also, a pleural effusion needed to be drained under local anesthesia in the same patient. The remaining complications were categorized as minor, scoring CCS: 1 in 15 patients and CCS: 2 in 6 patients. The minor complications were: band-aid allergy (n=1), hematoma (n=2), anemia (n=1), cardiac chest pain (n=1), dyspnea (n=2), fever of unknown cause (n=5), complicated urinary tract infection (n=5), neuropathy upper leg (n=1), hypotonic abdominal muscle (n=2), reversible sensibility loss of the arm (n=1), and embolism of an ocular artery (n=1). In two patients more than one post-operative complication was recorded. In those two patients, the complication that scored the highest Clavien score was used for statistical analysis.

Table 2 shows how the IO and PO complications are divided over the grade of anatomical complexity for both nephrometry indices. Both indices show that an increase of anatomical complexity is related to an increased risk for IO complications.

Table 2.

The Number and Percentages of IOC and POCs for Each Grade of Anatomical Complexity of the PADUA and RENAL Nephrometry Indices

	PADUA			RENAL
Tumor anatomical complexity	Tumor	IOC	POC	Tumor	IOC	POC
Low	42	6/42	8/42	48	6/48	7/48
		14.3%	19.1%		12.5%	14.6%
Moderate	38	6/38	6/38	48	12/48	12/48
		18.8%	15.8%		25.0%	25.0%
High	19	7/19	6/19	3	1/3	1/3
		36.8%	31.6%		33.3%	33.3%

Four patients were excluded for whom IOCs were not scored (except for conversion). POC and IOC are dichotomously scored for each procedure (yes vs no).

IOC=intraoperative complication; POC=postoperative complication; PADUA=preoperative aspects and dimensions used for anatomical classification; RENAL=radius; exophytic/endophytic; nearness; anterior/posterior; location.

Statistical results

Table 3 shows the results of the univariate analysis. For the risk of IO complications, there was a significant correlation (p<0.05) with the RENAL domains “R-size,” “N-nearness to the collecting system,” and “RENAL score.” The correlation with the domain “diameter” of the PADUA-index was also significant. The additional studied parameters studied tumor diameter (mm), surface (mm²), and volume (mm³) and were found significantly correlated with IOC as well.

Table 3.

Pearson's Correlations (r) of Parameters Using Univariate and if Appropriate Multivariate Analysis for IOC and POCs of Laparoscopic Renal Mass Cryoablation

	IOC			POC
	Univariate		Multivariate	Univariate
	r	p-Value	p-Value	r	p-Value
Age	0.054	0.601		0.068	0.503
BMI	−0.060	0.562		0.192	0.057
CCI	−0.028	0.786		0.149	0.141
a-CCI	0.002	0.983		0.170	0.092
Approach trans/retro	0.105	0.309		−0.075	0.459
Preoperative GFR-MDRD	−0.162	0.118		0.035	0.733
Solitary kidney	0.060	0.561		−0.057	0.576
RENAL
R (size)	0.227	0.027^a	0.027^b	0.035	0.728
E (exophytic/endophytic)	0.200	0.052		−0.015	0.885
N (nearness to the collecting system)	0.218	0.034^a	0.386	0.230	0.022^a
L (lines)	0.000	1.000		0.102	0.315
Hilar suffix	0.127	0.221		0.044	0.663
RENAL score	0.204	0.047^a	0.505	0.165	0.103
RENAL complexity grade	0.152	0.142		0.185	0.066
PADUA
Diameter	0.227	0.027^a	0.027^b	0.035	0.728
% of tumor deepening	0.158	0.126		−0.005	0.964
Relation UCS	0.140	0.175		0.183	0.069
Longitudinal location	−0.011	0.919		0.065	0.521
Rim location	0.129	0.212		0.108	0.287
PADUA score	0.198	0.054		0.175	0.083
PADUA grade	0.175	0.090		0.122	0.228
Additional
Tumor diameter (mm)	0.271	0.008^c	0.008^b	0.178	0.079
Tumor surface (mm²)	0.271	0.008^c	0.008^b	0.178	0.079
Tumor volume (mm³)	0.286	0.005^c	0.005^b	0.133	0.191
Medial location (PADUA)	0.127	0.221		0.044	0.663
Upper pole (PADUA)	−0.120	0.249		−0.129	0.204
Upper pole RENAL	−0.120	0.249		−0.129	0.204

Significant p-values <0.05.

Values of all diameter-related parameters were obtained by using only one of these at the time of multivariate analysis.

Significant p-values <0.01.

For the risk of PO complications, there was a significant correlation found for the RENAL domain “N-nearness to the collecting system.” Other RENAL domains, such as score and grade, and the PADUA domains, also score and grade, showed no significant relation with PO complications.

The additionally studied parameters (PADUA medial location, PADUA upper pole location, and RENAL upper pole location) were not correlated with a significant risk for IO complications nor for PO complications.

At multivariate analysis with IO complication as the independent variable, only tumor volume was a determining factor (p=0.005, predictive value of the model R=0.286 and R ²=0.082). That is, tumor diameter (in mm), categorized diameters (PADUA and RENAL), and surface were outweighed by tumor volume. However, when we used tumor diameter alone, in agreement with clinical practice, the predictive value of the model was R=0.271 (R ²=0.074, p=0.008). For PO complications, no multivariate analysis was performed, since the RENAL domain “N-nearness to the collecting system” was the only significant predicting factor.

The tumor diameter in millimeters, was used to establish a threshold diameter that predicted the occurrence of IO complications. The odds ratio with a 95% confidence interval for the occurrence of IOC at the cut-off diameters 30 mm (≤30 or >30), 35 mm (≤35 or >35), and 40 mm (≤40 or >40), was 4.54 (1.479–13.923), 5.32 (1.763–16.004), and 4.80 (1.078–21.370), respectively. Therefore, the best discerning threshold of tumor diameter above which an increased risk for IO complications performing LCA exists, was set at 35 mm.

Discussion

The first objective of this retrospective study was to evaluate the utility of the RENAL and PADUA nephrometry indices for predicting the risk for IO and PO complications in a cohort of patients that underwent LCA for a small renal mass. It showed a significant correlation (p=0.041) between the RENAL score and the risk for IO complications. However, the PADUA score did not (p=0.054). Although, there was a clear increase of IO complications in relation with increased complexity grade of both indices, this was not significant. Additionally, this study showed no significant correlation between PO complications and the score and grade of both indices. However, the indices are meant to describe tumor anatomical complexity in a standardized and categorical manner, but are not primarily designed to predict the surgical efficacy, IO and PO complication.^3,4 Some domains of the indices showed a significant correlation that allows one to predict IO and PO complications risk using univariate analysis, hence, all were not determining factors for multivariate analysis.

Because factors other than the components of the RENAL and PADUA indices may influence the risk for IOC, we assessed the relation between additional parameters and the risk for IOC. First, the approach and subsequent presentation for perpendicular cryoprobe introduction of a tumor located at the renal upper pole can be demanding and, therefore, poses the risk of incorrect probe placement. However, in the present study, the parameter “upper pole location” for tumors located at the upper renal pole scoring PADUA-Longitudinal line: 1 or RENAL-Lines: 1 showed no significant correlation with the risk for IOC. Second, medial and hilar tumors can require longer operative dissection time due to the proximity of hilar vessels or pyelum. Earlier reports have shown that hilar tumors increased the risk of complications performing LCA.^21,22 In the RENAL index, a hilar tumor is addressed as a suffix to the nephrometry sum and is considered as an additional anatomical complexity factor. From the domain PADUA-Rim location, the tumors were selected with a score of 2, which reflects a medial location. However, no significant correlation was found between IOC and these medial/hilar parameters. Also, since the surgical approach was transperitoneal or retroperitoneal, it showed no significant correlation for the risk of IOC. It should to be noted that in this series the number of retroperitoneal approached LCA procedures annually decreased as a result of the introduction of CT guided percutaneous CA.

Using multivariate analysis, the tumor diameter, measured in millimeters, was a determining factor for the prediction of surgical complications of LCA. The domains “diameter” of the RENAL and PADUA indices were both significantly correlated with the risk for IOC but were not a determining factor using multivariate analysis. A limitation of the two nephrometry indices is that they are conducted by categorically scoring anatomical parameters reflecting the event of complicated surgery. However, the reference, or cut-off, for the categorical index per parameter is arbitrary. Renal tumor diameter scores 0–4, 4–7, and >7 cm are categorized (1, 2, and 3 points, respectively) and seem to follow the latest TNM-classification in the same fashion.²³ In a head to head comparison for scoring tumor diameter, we showed that the noncategorized method has a stronger relation with the risk for IOC than the categorized method of each of the nephrometry indices. Earlier studies clarified that tumor diameter is an important metric for complications related to LCA. Lehman et al. reported that tumor size appeared to be a key metric for incomplete ablations and the risk for complications following LCA (44 patients; 51 tumors).²⁴ All 13 complications (21 patients) were found at tumors >3 cm diameter. This present study confirms that patients with a larger tumor diameter have an increased risk for IOC. The threshold diameter of 35 mm (odds ratio: 5.32; 95% confidence interval: 1.76–16.04) was found to be predictive for an increased risk for IOC performing LCA.

The RENAL and PADUA indices are similar in their methodology and describe tumor location categorically. Despite the variations of categories between the indices, they both are used to assess the risk for complications for renal tumor surgery. However, a head to head comparison between the two indices is somewhat confusing because of differences such as the total amount of domains used, the definition of the sinus lines, and the evaluation of the anatomical relationship between the tumor and the urinary collecting system (or renal sinus). The PADUA “score” (6–14 points) is the total sum of six anatomical components, whereas, the RENAL “score” (4–12 points) is the total sum of four anatomical components. In the current study, this is reflected in the total sum of each scoring method for the same tumor, which results in the grading into different risk groups for each complexity index. We clearly noticed a shift toward increased complexity using the PADUA-index compared to the RENAL-index. This difference may have made the comparison of the predictive outcome of both indices in this series more difficult. Another concern is that both indices score equally for tumor diameter (1–3 points); however, the weight of this domain is different for the total sum of each index. Therefore, the score or complexity grade does not reflect the contribution of each parameter. This has to be taken into account when the two indices are compared. For a comparison between the PADUA and RENAL nephrometry this study population was too limited. Before starting this study no power analysis was performed. However, the results reported may support the study groups during the design of new studies.

A single staff urologist assessed the PADUA and RENAL nephrometry scores in this study. This might be considered as a limitation of the study. However, several studies reported that the RENAL nephrometry index has good interobserver reliability.^25
–27 However, it should be pointed out that these studies showed that the interobserver agreement was moderate for each of the components of the indices.

It can be questioned whether all POCs in this study are related to the anatomical complexity of the tumor or to general surgical procedure and patient comorbidity factors. Simhan et al. reported the incidence of complications of PN categorized by organ system.⁸ They noted that genitourinary complication rates are significantly different between the complexity groups (p<0001), whereas no clear trends corresponding to the complexity and other organ system complications were found. Using a population based sample, Joudi et al. reported that the risk for complications following partial and RN is significantly higher in patients with a CCI greater than 2.²⁸ The present study shows independently that, CCI, age, or combined in the a-CCI had no significant correlation with complications performing or following LCA. Accordingly, current principal guidelines consider LCA as a viable alternative to PN, especially for patients with an increased comorbidity and/or high-surgical risk.^1,2 The data of this study show that increased comorbidity in elderly patients does not significantly affect the risk for IOC or POC at LCA. Clearly, comorbidity and age are always taken into account when counseling patients. However, this study design was not adjusted for this selection bias.

It can be suggested that IOC's performing LCA relates to a surgeon's experience. However, at the start of this study, the surgeon was well trained in laparoscopy and had performed >50 LCA procedures in other institutions since 2004. Therefore, the complications as scored in this study seem not to be affected by the learning curve of LCA surgical skills.

Currently, anatomical complexity systems are increasingly implemented in the decision-making process for patients with clinical stage T1 renal mass. However, the majority of studies reported the relationship between ACS with partial or RN. Canter et al. concluded that the RENAL-index could be used for standardizing the reporting of solid renal masses and effectively stratifying the extirpative treatment type.²⁹ Today, active surveillance and ablative therapies are also recognized as viable treatment strategies.^1,2 In addition to surgical treatment decision making, the ACS's are used to objectify the morbidity, functional and pathologic outcomes of nephron-sparing surgery. Therefore, the ACS needs to be validated for all viable treatments and needs to allow for effective comparisons. Also, a threshold needs to be established and validated for each component of the PADUA and RENAL indices.

The design of this study is a major limitation because of the probability of selection bias. However, the cohort of the study is considered representative compared to other series of LCA. Further, the study is relevant because histology is attained in all cases. This enables one to interpret the impact of IOC and POC in relation to the anatomical complexity of renal cancer treated with LCA.

To our knowledge, this single center study is the first study to assess the PADUA and RENAL indices for patients that underwent LCA. In a multi-institutional study, Okhunov et al. report that the RENAL index predicts the complications at LCA.¹² They identified 77 patients with a mean tumor size of 2.6 cm diameter with available preoperative imaging. On multivariate analysis, the RENAL nephrometry score was independently associated with a higher risk of POCs (odds ratio: 2.23, 95% confidence interval: 1.05, 2.11, p=0.008). The authors propose a cut-off RENAL score of 8 for identifying those patients that are most likely to benefit from LCA. After an univariate analysis of the present study sample size of 99 LCA-procedures, we noticed a significant correlation between the occurrence of IOCs and the RENAL nephrometry score. However, the sample size of these retrospective studies is limited and this hypothesis will have to be tested in future studies. So far, no other study has reported the PADUA nephrometry score in association with LCA.

Conclusions

For the occurrence of complications after laparoscopic renal tumor CA, this single center study demonstrated that the score and grade-category assessed by the RENAL and PADUA indices are not determining factors using multivariate analysis. However, using univariate analysis, the RENAL nephrometry score is associated with a higher risk for IOCs but not for POCs. The categorizing method of the nephrometry indices limits its use for the evaluation of LCA. This study showed that tumor size is a significant predictor for the risk of IOCs. The noncategorized method of scoring tumor diameter showed a more significant correlation than the categorized method of the nephrometry indices. A threshold diameter of 35 mm was thereby established. Further evaluation in larger cohorts of laparoscopic renal tumor CA is needed to validate the anatomical classification systems.

Footnotes

Disclosure Statement

Brunolf W. Lagerveld, MD, works as a proctor in laparoscopic and percutaneous renal mass cryoablation on behalf of Galil Medical.

Abbreviations Used

References

Campbell

, Novick

, Belldegrun

, et al. Practice Guidelines Committee of the American Urological Association. Guideline for management of the clinical T1 renal mass. J Urol, 2009; 182:1271–1279.

Ljunberg

, Cowan

, Hanbury

, et al. European Association of Urology Guideline Group. EAU guidelines on renal cell carcinoma: The 2010 update. Eur Urol, 2010; 58:398–406.

Ficarra

, Novara

, Secco

, et al. Preoperative aspects and dimensions used for an anatomical (PADUA) classification of renal tumours in patients who are candidates for nephron-sparing surgery. Eur Urol, 2009; 56:786–793.

Kutikov

, Uzzo

. The R.E.N.A.L. nephrometry score: A comprehensive standardized system for quantitating renal tumor size, location and depth. J Urol, 2009; 182:844–853.

Pierorazio

, Patel

, Feng

, et al. Robotic-assisted versus traditional laparoscopic partial nephrectomy: Comparison of outcomes and evaluation of learning curve. Urology, 2011; 78:813–819.

Aboumarzouk

, Stein

, Eyraud

, et al. Robotic versus laparoscopic partial nephrectomy: A systematic review and meta-analysis. Eur Urol, 2012; 62:1023–1033.

Klatte

, Grubmüller

, Waldert

, et al. Laparoscopic cryoablation versus partial nephrectomy for the treatment of small renal masses: Systematic review and cumulative analysis of observational studies. Eur Urol, 2011; 60:435–443.

Simhan

, Smaldone

, Tsai

, et al. Objective measures of renal mass anatomic complexity predict rates of major complications following partial nephrectomy. Eur Urol, 2011; 60:724–730.

Mottrie

, Schatterman

, De Wil

, et al. Validation of the preoperative aspects and dimensions for an anatomical (PADUA) score in a robot-assisted partial nephrectomy series. World J Urol, 2011; 31:799–804.

10.

Hew

, Baseskioglu

, Barwari

, et al. Critical appraisal of the PADUA classification and assessment of the R.E.N.A.L. nephrometry score in patients undergoing partial nephrectomy. J Urol, 2011; 186:42–46.

11.

Reyes

, Canter

, Putnam

, et al. Thermal ablation of the small renal mass: Case selection using the R.E.N.A.L.-nephrometry score. Urol Oncol, 2012; 31:1292–1297.

12.

Okhunov

, Shapiro

, Moreira

, et al. R.E.N.A.L. nephrometry score accurately predicts complications following laparoscopic renal cryoablation. J Urol, 2012; 188:1796–1800.

13.

Lian

, Guo

, Zhang

, et al. Single-center comparison of complications in laparoscopic and percutaneous radiofrequency ablation with ultrasound guidance for renal tumors. Urology, 2012; 80:119–124.

14.

Sisul

, Liss

, Palazzi

, et al. RENAL nephrometry score is associated with complications after renal cryoablation: A multicenter analysis. Urology, 2013; 81:775–880.

15.

Schmit

, Thompson

, Kurup

, et al. Usefulness of R.E.N.A.L. nephrometry scoring system for predicting outcomes and complications of percutaneous ablation of 751 tumors. J Urol, 2013; 189:30–35.

16.

Charlson

, Pompei

, Ales

, Mackenzie

. A new method of classifying prognostic comorbidity in longitudinal studies: Development and validation. J Chronic Dis, 1987; 40:373–383.

17.

Charlson

, Szatrowski

, Peterson

, Gold

. Validation of a combined comorbidity index. J Clin Epidemiol, 1994; 47:1245–1251.

18.

Dindo

, Demartines

, Clavien

. Classification of surgical complications: A new proposal with evaluation in a cohort of 6336 patients and results of a survey. Ann Surg, 2004; 240:205–213.

19.

Martin

RCG

, Brennan

, Jaques

. Quality of complication reporting in the surgical literature. Ann Surg, 2002; 235:803–813.

20.

Goldberg

, Grassi

, Cardella

, et al. Society of Interventional Radiology Technology Assessment Committee; International Working Group on Image-Guided Tumor Ablation. Image-guided tumor ablation: Standardization of terminology and reporting criteria. Radiology, 2005; 235:728–739.

21.

Hruby

, Reisiger

, Venkatesh

, et al. Comparison of laparoscopic partial nephrectomy and laparoscopic cryoablation for renal hilar tumors. Urology, 2006; 67:50–54.

22.

Hruby

, Edelstein

, Karpf

, et al. Risk factors associated with renal parenchymal fracture during laparoscopic cryoablation. BJU Int, 2008; 102:723–726.

23.

Sobin

, Gospodarowicz

, Wittekind

. International Union against Cancer (UICC). TNM Classification of Malignant Tumors, 7th ed. Chichester: Wiley-Blackwell, 2010.

24.

Lehman

, Hruby

, Phillips

, et al. Laparoscopic renal cryoablation: Efficacy and complications for larger renal masses. J Endourol, 2008; 22:1123–1128.

25.

Montag

, Waingankar

, Sadek

, et al. Reproducibility and fidelity of the R.E.N.A.L. nephrometry score. J Endourol, 2011; 25:1925–1928.

26.

Weight

, Atwell

, Fazzio

, et al. A multidisciplinary evaluation of inter-reviewer agreement of the nephrometry score and the prediction of long-term outcomes. J Urol, 2011; 186:1223–1228.

27.

Kolla

, Spiess

, Sexton

. Interobserver reliability of the RENAL nephrometry scoring system. Urology, 2011; 78:592–594.

28.

Joudi

, Allareddy

, Kane

, Konety

. Analysis of complications following partial and total nephrectomy for renal cancer in a population based sample. J Urol, 2007; 177:1709–1714.

29.

Canter

, Kutikov

, Manley

, et al. Utility of the R.E.N.A.L. nephrometry scoring system in objectifying treatment decision-making of the enhancing renal mass. Urology, 2011; 78:1089–1094.