Renal functional and surgical outcomes after robot-assisted partial nephrectomy for hilar vs non-hilar tumors: Trifecta and pentafecta evaluation

Abstract

BACKGROUND

Robot-assisted partial nephrectomy (RAPN) is well-suited for managing complex renal tumors, including those located in the renal hilum. However, studies directly comparing RAPN outcomes for hilar and non-hilar tumors, particularly in terms of comprehensive measures, such as trifecta and pentafecta, are still limited.

AIM

To evaluate whether tumor location in the renal hilum independently influences surgical and renal functional outcomes after RAPN, as assessed by trifecta and pentafecta criteria.

METHODS

This single-center retrospective cohort study evaluated outcomes of RAPN for hilar and non-hilar renal tumors treated from April 2016 to June 2023. Eligible patients had tumors ≤ 7 cm, no metastasis, and at least one year of follow-up. Propensity score matching was applied. Primary endpoints were trifecta and pentafecta achievement. All procedures were performed under ischemia without early unclamping. Multivariate logistic regression identified predictors of outcome achievement.

RESULTS

Of 350 patients, 324 met the inclusion criteria, consisting of 60 hilar and 264 non-hilar tumors. Trifecta achievement was similar between hilar (63.3%) and non-hilar groups (64.0%), with no significant differences in ischemia time, positive margins, or major complications. Pentafecta achievement rates were also similar (20.0% hilar vs 14.0% non-hilar, P = 0.237). Multivariate analysis identified R score, N score, and L score as predictors of pentafecta non-achievement. Surgeon experience and hilar tumor presence were predictors of pentafecta achievement. Hilar tumor location was not an independent determinant in the propensity-matched analysis, suggesting that the adjustment methods and sample size may have influenced the results.

CONCLUSION

RAPN achieved comparable trifecta and pentafecta outcomes for hilar and non-hilar tumors, supporting its viability for complex hilar tumors when appropriate patient selection and surgical experience are ensured.

Key Words: Robot-assisted partial nephrectomy; Hilar tumors; Renal cell carcinoma; Trifecta; Pentafecta; RENAL nephrometry score

Core Tip: This retrospective cohort study evaluated surgical and renal functional outcomes of robot-assisted partial nephrectomy for hilar and non-hilar renal tumors using trifecta and pentafecta metrics. While trifecta reflects perioperative quality, pentafecta incorporates renal functional preservation and chronic kidney disease progression, which are clinically relevant from a nephrological perspective. Using propensity score matching and multivariate analysis, we demonstrate that robot-assisted partial nephrectomy can achieve comparable pentafecta outcomes in hilar and non-hilar tumors when tumor complexity and surgical experience are appropriately considered, supporting the feasibility of nephron-sparing surgery for anatomically complex hilar tumors.

INTRODUCTION

Renal cell carcinoma is the most common type of kidney cancer. Partial nephrectomy (PN) is the standard treatment for small renal tumors. PN primarily aims to preserve renal function. Radical nephrectomy was widely performed in the past; however, it is associated with higher risks of renal dysfunction and reduced overall survival. Therefore, there is an increasing preference for PN due to its survival benefits, despite similar tumor control efficacy[1-4]. Guidelines from the European Association of Urology and the National Comprehensive Cancer Network recommend PN whenever feasible for T1a tumors (≤ 4 cm), with a growing trend toward PN for T1b tumors (4-7 cm)[5,6].

PN can be performed through various approaches, including open, laparoscopic, and robot-assisted surgery. The choice of approach typically depends on tumor complexity, often assessed using the RENAL nephrometry score[7]. Robot-assisted PN (RAPN) has become a preferred method, particularly as it has been reported to reduce warm ischemia time (WIT) compared with conventional laparoscopy[8,9]. Tumors located in the renal hilum are adjacent to major blood vessels and the ureter; thus, they present high surgical complexity[10]. The precision and articulated capabilities of robotic systems[11] make RAPN especially suitable for treating hilar tumors.

This study aimed to assess the safety and efficacy of RAPN for tumors in the renal hilum. Specifically, we analyzed the impact of tumor location on surgical outcomes, focusing on key performance metrics including postoperative complications, ischemia time, positive surgical margins, and preservation of renal function, evaluated through trifecta[12] and pentafecta outcomes[13].

MATERIALS AND METHODS

We performed a single-center retrospective observational study. We included patient data of RAPN performed for hilar tumors conducted from April 2016 to June 2023. Institutional Review Board approval was obtained from Kobe University Hospital (approval No. B230143). Because this study involved secondary analysis of routinely collected clinical data without additional interventions and posed minimal risk to participants, and consent was obtained via an opt-out process. Study information was publicly disclosed on the hospital’s official website, and patients were given the opportunity to decline participation at any time. The study was conducted in accordance with the principles outlined in the Declaration of Helsinki.

Inclusion criteria were patients with renal tumors ≤ 7 cm, without metastasis, and available for at least one year of postoperative follow-up. All patients underwent preoperative thin-slice enhanced computed tomography, which was processed using OsiriX (Pixmeo, Geneva, Switzerland) to create three-dimensional models of the tumor and surrounding vasculature. These three-dimensional models were displayed via the TilePro multi-input system alongside the standard endoscopic view on the robotic console, allowing real-time visualization of critical structures during surgery[14].

Hilar tumors were defined according to criteria by Hinata et al[15]: (1) Tumors located entirely between or crossing the polar lines; and (2) With margins within 5 mm of where the renal artery or vein enters the renal parenchyma. Propensity scores were calculated using covariates including age, sex, body mass index, performance status, comorbidities, laterality, preoperative estimated glomerular filtration rate (eGFR), tumor size, surgical approach, surgeon experience, and RENAL nephrometry components (E, N, and L scores). Nearest-neighbor matching was applied in a 1:1 ratio with a caliper distance of 0.2.

The primary outcomes assessed were trifecta and pentafecta achievement. Trifecta was defined as a combination of negative surgical margins, WIT < 25 minutes, and no major perioperative complications (Clavien-Dindo grade III or higher)[12]. Pentafecta included trifecta criteria plus the absence of significant renal function decline (defined as < 10% decrease in eGFR at 12 months) and no chronic kidney disease (CKD) progression at 3 months[13]. None of the cases were performed without ischemia, and early unclamp techniques were not used. The renal artery was released only after the completion of renal parenchymal suturing.

Statistical analyses were performed using EZR (version 1.65; Saitama Medical Center, Jichi Medical University, Saitama, Japan). Continuous variables were reported as medians with ranges because several perioperative variables demonstrated skewed distributions with potential outliers, and compared using the Mann-Whitney U test. Categorical variables were expressed as n (%) and compared with the χ² test. Independent predictors of trifecta and pentafecta outcomes were identified through multivariate logistic regression, with variables selected based on P < 0.1 in univariate analyses and clinical relevance such as tumor location (hilar vs non-hilar) and RENAL nephrometry score. Odds ratios with 95% confidence intervals were reported, with statistical significance set at P < 0.05.

RESULTS

A total of 350 patients underwent RAPN, with 330 patients meeting the criteria of at least one year of follow-up. Of the initial group, three patients passed away due to unrelated causes, 12 transferred to other hospitals, and five discontinued follow-up within one year for personal reasons. Two patients required an additional PN for a contralateral kidney tumor, and four patients lacked renal function measurements at the one-year mark. Ultimately, 324 patients were included in the analysis.

Based on the Hinata et al[15] criteria, 60 patients were classified as hilar tumors, and 264 as non-hilar tumors. None of the cases required conversion to open surgery or radical nephrectomy. Patient characteristics are detailed in Table 1. Significantly higher RENAL scores were observed in the hilar tumor group.

Table 1 Patient characteristics, n (%)/median (interquartile range).

Characteristics		Entire cohort				Propensity matched cohort
		Entire cohort, n = 324	Hilar tumor, n = 60	Non-hilar tumor, n = 264	P value	Hilar tumor, n = 60	Non-hilar tumor, n = 60	P value	SMD
Age (years)		66 (28-92)	66 (39-85)	66 (28-92)	0.909	66 (39-85)	66 (37-92)	0.956	0.011
Sex (%)	Male	230 (71.0)	44 (73.3)	186 (70.5)	0.753	44 (73.3)	41 (68.3)	0.688	0.110
BMI (kg/m2)		24.0 (14-45.2)	23.9 (17.3-35.3)	24 (14-45.2)	0.949	23.9 (17.3-35.3)	23.6 (15.7-32.6)	0.103	0.322
ECOG-PS (%)	0	279 (86.1)	54 (90)	225 (85.2)	0.616	54 (90)	54 (90.0)	1	< 0.001
	1	44 (13.6)	6 (10)	38 (14.4)		6 (10)	6 (10.0)
	2	1 (0.3)	0	1 (0.4)		0	0
Comorbidity (%)	Diabetes mellitus	85 (26.2)	17 (28.3)	68 (25.8)	0.745	17 (28.3)	43 (71.7)	1	< 0.001
	Hypertension	147 (45.4)	29 (48.3)	118 (44.7)	0.667	29 (48.3)	17 (28.3)
Laterality (%)	Right	177 (54.6)	34 (56.7)	143 (54.2)	0.775	34 (56.7)	31 (51.7)	0.714	0.100
	Left	147 (45.4)	26 (43.3)	121 (45.8)		26 (43.3)	29 (48.3)
Preoperative estimated glomerular filtration rate (mL/minute/1.73 m2)		70.0 (17.9-115.2)	71 (22.7-96.3)	69.6 (17.9-115.2)	0.920	71 (22.7-96.3)	68.6 (25.4-100.1)	0.902	0.017
Preoperative CKD staging (%)1	I	26 (8.0)	2 (3.3)	24 (9.1)	0.516	2 (3.3)	6 (10.0)	0.402	0.324
	II	197 (60.8)	39 (65.0)	158 (59.8)		39 (65.0)	33 (55.0)
	III	91 (28.1)	17 (28.3)	74 (28.0)		17 (28.3)	20 (33.3)
	IV	10 (3.1)	2 (3.3)	8 (3.0)		2 (3.3)	1 (1.7)
Tumor size (mm)		3.1 (11-69)	3.3 (10-69)	3.0 (11-68)	0.134	3.3 (10-69)	3.4 (1.2-5.8)	0.994	0.007
Medical device (%)	DaVinci	319 (98.5)	59 (98.3)	260 (98.5)	1	59 (98.3)	59 (98.3)	1	< 0.001
	Hinotori	5 (1.5)	1 (1.7)	4 (1.5)		1 (1.7)	1 (1.7)
Approach (%)	Intra	199 (61.4)	33 (55.0)	166 (62.9)	0.304	33 (55.0)	34 (56.7)	1	0.034
Surgeon’s experience (cases > 20) (%)	≥ 20	216 (66.7)	45 (75.0)	171 (64.8)	0.172	45 (75.0)	42 (70.0)	0.683	0.112
R score (%)1	1	236 (72.8)	44 (73.3)	192 (72.7)	1	44 (73.3)	39 (65.0)	0.429	0.181
	2	88 (27.2)	16 (26.7)	72 (27.3)		16 (26.7)	21 (35)
E score (%)	1	115 (35.5)	15 (25.0)	100 (37.9)	0.105	15 (25.0)	16 (26.7)	0.893	0.102
	2	142 (43.8)	28 (46.7)	114 (43.2)		28 (46.7)	25 (41.5)
	3	67 (20.7)	17 (28.3)	50 (18.9)		17 (28.3)	19 (31.7)
N score (%)	1	36 (11.7)	2 (3.3)	34 (12.9)	0.047b	2 (3.3)	2 (3.3)	0.915	0.104
	2	55 (17.0)	8 (13.3)	47 (17.8)		8 (13.3)	6 (10.0)
	3	233 (71.9)	50 (83.3)	183 (69.3)		50 (83.3)	52 (86.7)
A score (%)1	A	75	29 (48.3)	109 (41.3)	0.569	29 (48.3)	29 (48.3)	0.720	0.149
	P	111	20 (33.3)	92 (34.8)		20 (33.3)	20 (33.3)
	X	148	11 (18.3)	63 (23.9)		11 (18.3)	11 (18.3)
L score (%)	1	102	0	102 (38.6)	< 0.001c	0	0	1	0.036
	2	93	18 (30.0)	75 (28.4)		18 (30.0)	19 (31.7)
	3	129	42 (70.0)	87 (33.0)		42 (70.0)	41 (68.3)
Renal score (%)1	4	9 (2.8)	9 (3.4)	0	< 0.001c	0	0	0.574	0.432
	5	27 (8.3)	2 (3.3)	25 (9.5)		2 (3.3)	1 (1.7)
	6	37 (11.4)	0 (0)	37 (14.0)		0 (0)	3 (5.0)
	7	56 (17.3)	4 (6.7)	52 (19.7)		4 (6.7)	2 (3.3)
	8	64 (19.8)	13 (21.7)	51 (19.3)		13 (21.7)	12 (20.0)
	9	79 (24.4)	24 (40.0)	55 (20.8)		24 (40.0)	21 (35.0)
	10	47 (14.5)	16 (26.7)	31 (11.7)		16 (26.7)	18 (30.0)
	11	5 (1.5)	1 (1.7)	5 (1.5)		1 (1.7)	3 (5.0)

^bP < 0.01.

^cP < 0.001.

¹Propensity unmatched.

SMD: Standardized mean difference; BMI: Body mass index; ECOG-PS: Eastern Cooperative Oncology Group Performance Status, CKD: Chronic kidney disease.

In terms of trifecta outcomes, there was no significant difference between the median WIT in the hilar group (22 minutes, range: 15-59) and in the non-hilar group (23 minutes, range: 11-51) (P = 0.463). The proportion of cases with WIT > 25 minutes was similar between the groups: 40.0% (24 cases) in the hilar group and 37.1% (98 cases) in the non-hilar group (P = 0.768). Positive surgical margins were absent in the hilar group; however, they were present in 1.1% (3 cases) in the non-hilar group, with no significant difference (P = 1.000). Clavien-Dindo grade III or higher complications occurred in 10% (6 cases) of the hilar group and 6.8% (18 cases) of the non-hilar group (P = 0.413). Trifecta achievement rates were similar, with 63.3% (38 cases) in the hilar group and 64.0% (169 cases) in the non-hilar group (P = 1.000). To evaluate potential survivorship bias, trifecta achievement was assessed in the entire cohort of consecutive RAPN cases, including those excluded from the 12-month analytic cohort. Trifecta rates were 64.9% in the non-hilar group and 63.1% in the hilar group, which were comparable to the rates observed in the analytic cohort (64.0% and 63.3%, respectively), suggesting minimal impact of follow-up exclusion on perioperative outcomes (Supplementary Table 1).

For pentafecta outcomes, CKD stage progression at three months was observed in 35% (21 cases) of the hilar group and 36% (95 cases) of the non-hilar group (P = 1.000). At 12 months, 66.7% (40 cases) in the hilar group and 74.2% (196 cases) in the non-hilar group had reductions in kidney function to less than 90% of preoperative values, with no significant difference (P = 0.261). The pentafecta achievement rate was 20.0% (12 cases) in the hilar group vs 14.0% (37 cases) in the non-hilar group (P = 0.237).

Multivariate analysis for trifecta outcomes (Table 2) indicated that CKD stage 3 or 4 and an R score of 2 were independent predictors of trifecta non-achievement. In terms of pentafecta outcomes (Table 3), an R score of 2, an N score of 3, and an L score of 3 were predictors of pentafecta non-achievement. Surgeries performed by surgeons with experience exceeding 20 cases and the presence of a hilar tumor were independent predictors of pentafecta achievement.

Table 2 Univariate and multivariate analyses of factors predicting trifecta achievement.

	Univariate analysis			Multivariate analysis
	OR	95%CI	P value	OR	95%CI	P value
Age ≥ 66	0.697	0.442-1.10	0.122
Male	0.940	0.569-1.55	0.810
BMI ≥ 24	0.671	0.425-1.06	0.087
ECOG-PS ≥ 1	0.636	0.335-1.21	0.167
Diabetes mellitus	0.798	0.48-1.33	0.385
Hypertension	0.855	0.542-1.35	0498
Preoperative CKD stage ≥ 3	0.558	0.345-0.905	0.018	0.578	0.354-0.942	0.028a
Surgeon’s experience ≥ 20 cases	1.270	0.788-2.05	0.327
R score ≥ 2	0.478	0.29-0.788	0.004b	0.492	0.297-0.814	0.006b
E score ≥ 3	0.864	0.497-1.50	0.606
N score ≥ 3	0.624	0.369-1.06	0.079
L score ≥ 3	0.782	0.493-1.24	0.297
Intra approach	1.01	0.633-1.61	0.974
Hilar tumor	1.03	0.575-1.84	0.921	0.965	0.534-1.75	0.907
RENAL score ≥ 10	0.666	0.356-1.22	0.185

^aP < 0.05.

^bP < 0.01.

OR: Odds ratio; CI: Confidence interval; BMI: Body mass index; ECOG-PS: Eastern Cooperative Oncology Group Performance Status, CKD: Chronic kidney disease.

Table 3 Univariate and multivariate analysis of factors predicting pentafecta achievement.

	Univariate analysis			Multivariate analysis
	OR	95%CI	P value	OR	95%CI	P value
Age ≥ 66	0.886	0.482-1.63	0.697
Male	0.534	0.285-1.00	0.051
BMI ≥ 24	0.560	0.301-1.04	0.067
ECOG-PS ≥ 1	1.07	0.448-2.56	0.876
Diabetes mellitus	0.589	0.273-1.270	0.178
Hypertension	0.657	0.351-1.230	0.190
Preoperative CKD stage ≥ 3	0.864	0.442-1.690	0.670
Surgeon’s experience ≥ 20 cases	2.5	1.160-5.37	0.019a	3.73	1.64-8.49	0.002b
R score ≥ 2	0.328	0.135-0.802	0.015a	0.319	0.125-0.810	0.016a
E score ≥ 3	0.490	0.199-1.2	0.120
N score ≥ 3	0.455	0.243-0.853	0.014a	0.449	0.224-0.898	0.024a
L score ≥ 3	0.438	0.219-0.876	0.020a	0.306	0.138-0.681	0.004b
Intra approach	1.50	0.814-2.770	0.194
Hilar tumor	0.652	0.317-1.34	0.245	2.61	1.12-6.08	0.026
RENAL score ≥ 10	0.0915	0.0123-0.678	0.019a

^aP < 0.05.

^bP < 0.01.

OR: Odds ratio; CI: Confidence interval; BMI: Body mass index; ECOG-PS: Eastern Cooperative Oncology Group Performance Status; CKD: Chronic kidney disease.

A propensity-matched cohort was created, yielding 60 patients in each group. Propensity score matching retained 120 of 324 patients (37.0%), with 204 non-hilar cases excluded because suitable matches were not identified within the caliper. Covariate balance was achieved after matching. In the matched cohort, median WIT was 22 minutes (range: 12-59) in the hilar group and 24 minutes (range: 13-49) in the non-hilar group (P = 0.102). The proportion of cases with WIT > 25 minutes was 40.0% (24 cases) in the hilar group and 46.7% (28 cases) in the non-hilar group (P = 0.581). Positive surgical margins were absent in the hilar group and present in two cases (3.3%) in the non-hilar group (P = 1.000). Clavien-Dindo grade III or higher complications occurred in 10.0% (6 cases) of the hilar group and 5.0% (3 cases) of the non-hilar group (P = 0.491), with no significant difference in trifecta achievement rates (63.3% vs 55.0%, P = 0.458).

For pentafecta outcomes in the matched cohort, CKD stage progression at three months occurred in 35.0% (21 cases) of the hilar group and 40.0% (24 cases) of the non-hilar group (P = 0.706). At 12 months, 66.7% (40 cases) of the hilar group and 78.3% (47 cases) of the non-hilar group had an eGFR below 90% of the preoperative value (P = 0.220). The pentafecta achievement rate was 20.0% (12 cases) in the hilar group and 10.0% (6 cases) in the non-hilar group (P = 0.200).

DISCUSSION

The present study provides a comprehensive analysis of RAPN outcomes for hilar vs non-hilar renal tumors, utilizing a propensity score-matching approach to minimize confounding factors. Previous studies reported that robotic precision effectively managed hilar tumors, achieving outcomes comparable to non-hilar tumors when controlled for various factors[15-19]. However, these studies largely focused on trifecta outcomes, assessing short-term metrics including ischemia time, surgical margins, and perioperative complications. In the present study, no positive surgical margins were observed in the hilar group. Although this may appear counterintuitive given the higher tumor complexity, the overall positive margin rate in the entire cohort was very low (0.9%), with only three events recorded. The very small number of positive margins limits meaningful statistical comparison between groups and warrants cautious interpretation.

In addition, our study extends previous work by evaluating pentafecta outcomes, which incorporate long-term renal functional preservation in addition to perioperative and complication-related metrics, thereby providing a more comprehensive assessment of RAPN for complex hilar tumors. While trifecta primarily reflects perioperative quality and oncological safety, preservation of renal function represents a fundamental objective of nephron-sparing surgery. The definitions of trifecta and pentafecta applied in this study were not arbitrarily determined but were based on previously established and widely accepted criteria in the urologic literature[12,13]. These thresholds, including WIT < 25 minutes and < 10% eGFR decline at 12 months, have been consistently adopted to allow standardized reporting and facilitate comparison across studies. Therefore, we adhered to these validated definitions to maintain methodological consistency and interpretability. Accumulating evidence from prior nephrectomy studies has demonstrated that loss of nephron mass is associated with an increased risk of de novo CKD and adverse long-term outcomes[20], underscoring the clinical relevance of renal functional endpoints in comparative effectiveness analyses. Furthermore, previous studies broadly defined hilar tumors as those near the renal artery and vein; however, our study adopted precise criteria from Hinata et al[15], ensuring consistency in patient selection and outcome assessment. Notably, the overall pentafecta achievement rates in our cohort were modest. This likely reflects the stringent composite criteria of pentafecta, particularly the requirement for preserved renal function at 12 months. Therefore, the absence of a statistically significant difference between hilar and non-hilar tumors should be interpreted as demonstrating the feasibility of achieving comprehensive quality metrics in selected hilar cases, rather than indicating equivalence in surgical complexity or universal functional preservation.

Few studies have examined pentafecta achievement specifically for hilar tumors. Tyagi et al[17] reported a pentafecta rate of 12.1% for hilar tumors, which was similar to non-hilar cases. These findings are consistent with our results. In our study, the pentafecta rate was 20.0% (12/60) for hilar tumors and 10.0% (6/60) for non-hilar tumors, with no significant difference (P = 0.200). Multivariate analysis indicated that an R score of 2, N score of 3, and L score of 3 were significant predictors of pentafecta non-achievement, whereas surgeries performed by surgeons with experience in over 20 cases independently predicted pentafecta achievement. These findings align with previous studies[21-23]. Surgeon experience was dichotomized at 20 cases based on prior literature examining the learning curve in RAPN[24]. We acknowledge that surgical experience is inherently continuous and may involve nonlinear effects; however, in the present study, experience was included as a clinically interpretable covariate rather than as the primary focus of learning curve analysis.

Interestingly, although hilar tumors emerged as significant predictors of pentafecta achievement in the multivariate analysis, they did not show the same significance in the propensity matched cohort. This discrepancy may stem from differences in covariate adjustment methods, as multivariate analysis allows more detailed control of variables. The relatively small sample size of the propensity-matched cohort (60 patients per group) likely reduced the statistical power to detect moderate differences, particularly in multivariable-adjusted comparisons. Therefore, the lack of statistical significance in the matched analysis should be interpreted cautiously and may partly account for the discrepancy observed between the multivariate regression model and the matched cohort findings. Furthermore, hilar tumor location alone was not an independent determinant of overall complications or pentafecta achievement, once factors such as tumor size, surgeon experience, and RENAL score components were accounted for. Residual confounding factors and potential effect modifications, including interactions between tumor characteristics and surgeon experience, may further explain this variation. Further investigation in larger cohorts is warranted to better understand these associations.

Our results are consistent with those of Tyagi et al[17]. Our study employed a meticulous adjustment process, providing a more reliable basis for understanding hilar tumor outcomes in RAPN. Moreover, we standardized the definition of hilar tumors to ensure consistency. Hilar tumors were defined as renal masses near the renal artery or vein entry into the parenchyma, which inherently increase surgical complexity due to proximity to critical vessels and the collecting system[17-19,23,24]. In contrast to broader, less precise definitions in previous studies, we applied criteria from Hinata et al[15], categorizing tumors as hilar if located entirely between the polar lines or if their margin was within 5 mm of the renal artery or vein entry into the parenchyma. This precise definition ensures consistency in patient selection and outcome measurement, which enables accurate comparisons across studies and reliable evaluation of key outcomes such as WIT, complication rates, and renal function preservation.

This study had several limitations. First, as a retrospective observational study, it carries the risk of selection bias and confounding. Although we employed propensity score matching and multivariate analysis to adjust for known confounders, unmeasured factors may have influenced the outcomes. Second, the relatively small sample size, especially in the propensity-matched cohort with 60 cases per group, may have reduced the statistical power to detect moderate effect sizes. This limitation may partly explain the discrepancy between the multivariate regression analysis and the matched cohort results regarding the impact of hilar tumor location. Despite the limited sample size, this study represents the largest single-center study using strict Hinata criteria focused specifically on hilar tumors in RAPN. Third, as a single-center study conducted in a Japanese cohort, the findings may not be generalizable to institutions with different patient populations, surgical expertise, healthcare systems, or robotic platforms. Finally, renal functional outcomes were evaluated at predefined time points (3 months and 12 months) according to established pentafecta criteria; longitudinal trajectory analyses were not performed and may be considered in future studies.

CONCLUSION

This study suggests that RAPN achieves comparable trifecta and pentafecta outcomes for hilar and non-hilar renal tumors. Although hilar tumor location was associated with pentafecta achievement in the multivariate analysis, this association was not confirmed in the propensity-matched cohort, likely reflecting differences in adjustment methods and limited statistical power. Importantly, when tumor complexity and surgeon experience were appropriately accounted for, hilar tumor location itself was not an independent determinant of adverse surgical or renal functional outcomes. Overall, these findings support the feasibility of RAPN for anatomically complex hilar tumors when performed with appropriate patient selection and surgical expertise.