Partial nephrectomy (PN) remains the standard treatment for cT1a renal tumors (1, 2) and increasingly being used to manage more complex masses (3). Due to the similar oncologic outcome, faster recovery, and reduced blood loss and wound complications, PN has transitioned from open to the minimally invasive approach. Before the advent of robot surgical system, laparoscopic partial nephrectomy (LPN) has been widely performed. However, continued concern about prolonging renal artery clamping time and the complexity of suturing and excision are obstacles to the use of LPN. In China, robotic partial nephrectomy (RPN) has been more and more widely used in treating renal masses, especially for more complex lesions. Due to the advantaged of robot surgical system, RPN provides improvements in estimated blood loss, ischemia time, and postoperative hospital stay to LPN (4).

RPN can be conducted through transperitoneal or retroperitoneal approach (5). In China, RPN was initially performed exclusively via the abdominal approach. Because of the extensive experiences in retroperitoneal LPN (6, 7), we have tried to perform retroperitoneal robotic partial nephrectomy (RRPN) for some patients with posterior renal tumors. Many studies have compared the outcomes between transperitoneal robotic partial nephrectomy (TRPN) and RRPN for patients with renal tumors, including renal masses in different locations (8–10) or only lateral (11) or posterior (12–14) tumors. Recently, a meta-analysis summarizing the results from these studies has been published (15). They found that RRPN can obtain more favorable outcomes than TRPN, including shorter operative time, less estimated blood loss, less minor complications, and shorter hospital stay.

For complete upper pole renal tumors, RPN can be performed by transperitoneal or retroperitoneal approach. The transabdominal approach is familiar to urologists, and adequate operating space to avoid instruments collision. However, because of the proximity of the abdominal organs, it was more difficult to expose renal hilum and tumors. In contrast, the advantage of the retroperitoneal approach is that it reduces morbidity and speeds recovery by avoiding abdominal and unobstructed access to the hilum (14, 16). Hence, we initially compared the perioperative, functional and oncological outcomes of TRPN and RRPN for complete upper pole renal tumors.

In total, 108 patients were included in the present study, 48 of them underwent TRPN and 60 underwent RRPN. Table 1 shows demographics and disease characteristics. No significant difference was identified between the TRPN and RRPN groups in terms of demographics (age, gender, BMI, ASA score, CCI score, presence of diabetes or hypertension, history of abdominal surgery), laterality distribution (p = 0.702), median tumor size (2.8 vs. 3.3 cm, p = 0.840), median RENAL score (6 vs. 6, p = 0.908), median preoperative serum creatinine (69.2 vs. 74.2 µmol/L, p = 0.969), and median preoperative eGFR (97.3 vs. 97.6 ml/min/1.73 m², p = 0.951). When classified by the complexity of RENAL score, no significant difference was identified between the TRPN and RRPN groups in terms of low (54.2% vs. 55.0%), moderate (45.8% vs. 45.0%), and complex (0.0% vs. 0.0%, p = 1.000). Analyzing the “A” (anterior/posterior) domain of RENAL score, no significant difference was identified between the TRPN and RRPN groups in terms of anterior (25.0% vs. 23.3%), posterior (45.8% vs. 41.7%), not determined (29.2% vs. 35.0%, p = 0.853).

Table 2 shows the perioperative results. Patients undergoing TRPN had more estimated blood loss (50 vs. 40 ml, p = 0.004). There were no significant differences between the TRPN and RRPN in operative time (110 vs. 114 min; p = 0.870), ischemia time (19 vs. 18 min, p = 0.248), transfusion rate (2.1% vs. 0.0%, p = 0.444), positive margin rate (0.0% vs. 3.3%, p = 0.502), length of hospital stay (11 vs. 11 days, p = 0.579), and postoperative complication rate (25.0% vs. 13.3%, p = 0.140).

Table 3 shows the pathological, renal, functional, and oncological outcomes. Most patients were proven to be clear cell renal cell carcinoma. There were no significant differences between the TRPN and RRPN in tumor histology (p = 0.922), pT stage (p = 0.268), Fuhrman grade (p = 0.699), tumor necrosis rate (4.2% vs. 6.7%, p = 0.691). For postoperative renal function, no significant difference was identified between the two groups in 1-day ΔeGFR rate (14.2% vs. 17.1%, p = 0.581) and 12-month ΔeGFR rate (9.0% vs. 7.1%, p = 0.449). During the similar follow-up time (63.1 vs. 58.5 months, p = 0.382), there were no significant differences in local recurrence rate (2.1% vs. 1.7%, p = 1.000) and distant metastasis rate (2.1% vs. 3.3%, p = 1.000).

Table 4 shows pentafecta outcomes between TRPN and RRPN. The two groups had similar pentafecta rates (50.0% vs. 55.0%, p = 0.699). When pentafecta was classified into individual elements, no significant difference was identified in negative margins (100.0% vs. 96.7%, p = 0.502), no complication (75.0% vs. 86.7%, p = 0.140), ischemia time ≤25 min (81.3% vs. 86.7%, p = 0.596), eGFR recovery to >90% baseline (72.9% vs. 75.0%, p = 0.828), and CKD upstaging free (100.0% vs. 96.7%, p = 0.502). Table 5 shows univariable and multivariable analyses of factors related to pentafecta achievement. In univariable analysis, factors with p < 0.10 included tumor size, preoperative eGFR, and RENAL score. These factors together with surgical type were entered into multivariable analysis. The results showed that only decreasing RENAL score [OR, 0.641 (95% CI, 0.455–0.904); p = 0.011] was independent risk factor related to pentafecta achievement, but not surgical type (p = 0.600).

Robotic partial nephrectomy has been more and more widely used in treating renal masses in China and the USA (22), the changing trends in the approach to partial nephrectomy like to the treatment of other genitourinary conditions (23). RPN can be conducted with transperitoneal or retroperitoneal approach (5). The transperitoneal approach is familiar to urologists and adequate operating space to avoid instrument collisions. However, because of the proximity of the abdominal organs, it was more difficult to expose renal hilum and tumors. In contrast, the advantage of the retroperitoneal approach is that it reduces morbidity and speeds recovery by avoiding abdominal and unobstructed access to the hilum (14, 16). Although the comparative study of TRPN and RRPN in renal cancer has been well advanced, relevant data are still needed for the complete upper polar tumor subgroup.

In the present study, we initially compared the perioperative, functional, and oncological outcomes of these two surgical approaches for patients with complete upper pole renal tumors. At first, demographics and disease characteristics were compared between TRPN and RRPN. There were no significant differences in age, gender, BMI, ASA score, CCI score, chronic disease history, tumor size and complexity, and preoperative renal function. Generally, transperitoneal approach was more often chosen for anterior tumors, and retroperitoneal approach was more often chosen for posterior tumors. Analyzing the “A” domain of RENAL score, no significant difference was identified between the TRPN and RRPN groups with regard to anterior (25.0% vs. 23.3%), posterior (45.8% vs. 41.7%), and not determined (29.2% vs. 35.0%, p = 0.853). Therefore, there was good comparability between the two groups.

Previously, many studies have compared the outcomes between TRPN and RRPN for patients with renal masses (8–13, 24, 25). Most of them have identified advantages of RRPN, such as shorter operating time and ischemia time, less blood loss, and shorter hospital stay, especially for lateral or posterior tumors. Recently, we have included all studies with good comparability to perform a meta-analysis for this issue. The results showed that RRPN can obtain more favorable outcomes than TRPN, including shorter operative time, less estimated blood loss, less minor complications, and shorter hospital stay (15). However, besides slight advantage in estimated blood loss was found for RRPN, no significant difference was identified for other perioperative, functional, and oncological outcomes. All of the surgical procedures in our study were performed by skilled, high-volume surgeons. Experience with the technique may overcome the disadvantages of each surgical approach. According to our results, RRPN can obtain shorter ischemia time and lower rate of postoperative complications. However, the difference did not obtain statistical significance, which might be due to insufficient sample size. Moreover, the largest study comparing TRPN and RRPN to date reported similar results. After propensity score matching, 768 patients treated with TRPN or RRPN from global multi-institutions were analyzed. RRPN was proven to obtain a less estimated blood loss. No differences were observed between TRPN and RRPN in terms of operative and ischemia time, complications, length of stay, and positive surgical margins (26).

In our study, the perioperative, functional, and oncological outcomes were good, similar to those in other cohorts. Previously, we have reported the outcomes of 603 patients undergoing RPN. The rates of pentafecta achievement and each component were similar to the present study (27). Histopathological examination revealed that most of the patients had malignant tumors. Since there were no differences in tumor size, ischemia time, pT stage, Fuhrman grade, and tumor necrosis, it was understandable that these two approaches achieved comparable renal functional and oncological outcomes. Moreover, the renal functional and oncological outcomes reported in our study were similar to previous literatures (1, 2).

The perioperative outcomes of partial nephrectomy can be affected by many factors (28). As a comprehensive evaluation system, pentafecta achievement was also used to evaluate surgical outcomes of TRPN and RRPN. Because perioperative and functional outcomes were similar in both groups, there were no significant differences between each component. After synthesizing the results of five components, the pentafecta achievement rates of TRPN and RRPN were similar (50.0 vs. 55.0%, p = 0.699). Logistic regression analyses showed that only decreasing RENAL score (OR, 0.641 (95% CI, 0.455–0.904); p = 0.011) was an independent risk factor related to pentafecta achievement, but not surgical type (p = 0.600). About this issue, many previous studies have reported relevant results. Stroup et al. (10) have applied pentafecta to compare TRPN and RRPN, and factors related to lack of pentafecta outcome was conducted. The results showed that RENAL score and baseline eGFR were independent risk factors. Choi et al. (9) have analyzed 566 consecutive cases who were treated with RPN by a single surgeon to compare TRPN and RRPN for localized renal masses. Multivariable analysis identified that serum hemoglobin and tumor size were predictors of pentafecta achievement. Sharma et al. (29) have externally validated SPARE score in predicting pentafecta outcomes following RPN; the data of 201 patients undergoing RPN were analyzed. On multivariate analysis, age, preoperative eGFR, and SPARE score were predictors for pentafecta achievement. Different exclusion criteria, study subject, and relevant variables may be partly responsible for the inconsistent results.

There were several limitations for our study. Firstly, the results were limited by retrospective design with single-center inadequate sample size. Inherent selection bias in analyses can be controlled. Nevertheless, the similarity in demographic characteristics and disease features (including tumor complexity) between the two groups suggests their comparability. Secondly, all operations are performed by experienced surgeons. Junior surgeons should interpret these results with caution, choosing of surgical approach should be based on their experience and preference. Despite these limitations, our study initially compared TRPN and RRPN for complete upper pole renal tumors. Demographics, disease characteristics, perioperative outcomes, pathological, renal functional, and oncological outcomes were comprehensively reported and compared.

In summary, TRPN and RRPN can provide good and comparable results in perioperative, function, and oncological outcomes in patients with upper pole renal tumors. Both surgical approaches remain viable options in the treatment of these patients. The choice of surgical approach should be based on relevant experience and the preference of the surgeon.

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.

The studies involving human participants were reviewed and approved by the Ethics Committee of Chinese PLA General Hospital. The patients/participants provided their written informed consent to participate in this study.

Study concepts and design: XZ, XM, and LG. Data acquisition: LG, WZ, JX, YX, and XZ. Quality control of data and algorithms: LG, BW, and QC. Data analysis and interpretation: LG, DS, and HL. Statistical analysis: LG, WZ, and JX. Manuscript preparation: LG, WZ, and JX. Manuscript editing: BW and HL. Manuscript review: XZ and XM.

This work was supported by the National Natural Science Foundation of China (Grant 82100820).

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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