Discussion
The primary concern in the treatment of small renal masses with RN is the loss of kidney function. Thus, PN has become the gold standard approach when technically feasible. The literature supports the advantages of PN (9-13). Among Turkish patients, there are similar rates of PN and RN for cT1 renal masses, making this dataset suitable for analysis. This analysis has shown that there was a significant difference in OS between patients undergoing PN and RN. Furthermore, no significant adverse effect of age on OS was evident. The majority of studies have shown that renal function preservation is correlated with survival, and previous retrospective studies with large patient numbers suggested that renal function was an independent prognostic factor for non-cancer-related mortality. (2,17). In contrast, a prospective randomized controlled trial by the EORTC suggested that RN resulted in superior overall survival compared with PN (10-year overall survival: 81.1% vs. 75.7%; HR: 1.51, p =0.02) (9). Furthermore, Liek et al . showed that significant survival benefits were only seen in male patients <75 years treated with PN (p =0.0005), and there was no significant difference between the groups among male patients >75 years and female patients (p =0.736, p =0.175, and p =0.191, respectively) (11). Conversely, Mir et al . compared PN and RN in very elderly (>75 years) patients, and PN yielded a benefit with regard to cancer-specific mortality (HR: 0.19, 95% CI: 0.04–0.97;p =0.05), but there was no significant benefit with regard to either overall mortality or non-cancer-specific mortality (18). In agreement with these results, in our study, we did not find an association between age (subgroups; <49, 50-64, and >65 years) and OS.
In general, most of the studies published in the literature so far have shown that PN is associated with a lower risk of CKD and survival benefits (2,17). Tan et al. assessed patients under age 50 who were treated for renal masses with PN and RN and reported that there was no significant difference in overall survival between the groups (HR: 0.83, 95% CI: 0.63-1.10, p =0.196) (19). Based on their findings, the authors claimed that surgically induced CKD, rather than medical CKD, is associated with a lower risk of progression of renal insufficiency (20,21).
The present study showed a significant difference in the decrease in the GFR between the PN and RN groups, regardless of age, sex, or comorbidities. Finally, PN for T1 tumors was the most significant factor affecting the preservation of renal function. A recent study compared retroperitoneal laparoscopic partial and radical nephrectomy and showed similar preoperative and postoperative eGFR levels (p=0.63 and p=0.15, respectively). Nevertheless, the decrease in eGFR levels was significantly greater in the RN cohort, which agrees with our results (22). In contrast, Cooper et al . assessed the outcomes of percutaneous radiofrequency ablation, partial nephrectomy, and radical nephrectomy in cT1 renal cancer patients and demonstrated similar preoperative and postoperative eGFR values. There was no significant difference between PN and RN (p =0.74 and p =0.73, respectively) (23). Another important finding of the Cooper study was a similar need for dialysis in the two groups (p=0.29).
New evidence has shown that patients with a baseline eGFR below 85 ml/min were at risk for reduced renal function and higher cancer-specific mortality unless their postoperative eGFR was maintained above 60-65 mL/min, and PN should be selected for patients with any level of preoperative renal insufficiency (24). Additionally, published evidence has shown that the eGFR is an important prognostic factor and that the prognosis was worse when the eGFR fell below 45 mL/min/1.73 m2 after surgery (21). Another study by Takagi et al . assessed 95 patients with renal insufficiency who underwent PN and RN for T1a-T2 renal cell carcinoma and demonstrated that PN resulted in significantly superior preservation of renal function than RN (absence of CKD 64% vs. 22% in PN and RN, respectively) (25). Our findings are in agreement with those of Takagi et al .. When an arbitrary cut-off value of 90 mL/min/1.73 m2 was used for the GFR, among patients with a baseline GFR<90 mL/min/1.73 m2, renal function was significantly better preserved in the PN cohort, and the difference between the PN and RN cohorts became more significant. The eGFR level had returned to close to the baseline level by the third postoperative year in the PN cohort.
Several studies have attempted to identify the factors affecting changes in the eGFR and to predict who will benefit from PN or RN. Bhindi et al.  reported that older age, diabetes, and a worse preoperative eGFR were associated with a worse postoperative eGFR in the RN cohort, but in the PN cohort, diabetes was not associated with a worse postoperative GFR (p=0.4) (16). Comorbidities were not associated with OS in our study because the duration of the disease was short, and patients with comorbidities were more likely to undergo PN. The authors emphasized that the sparing of nephrons alone is not sufficient to achieve this in the PN group, and optimal diabetes control is essential. Other studies indicated that preoperative parenchymal quality, the volume of the preserved parenchyma,(10) and ischemia duration are the most powerful factors affecting postoperative GFR levels (26). In this study, we showed that there was no statistically significant adverse effect of comorbidities such as coronary artery disease, diabetes, and hypertension on the change in the GFR in either group and the major loss of renal parenchyma in RN is the most important factor.
The surgical approach is another point of discussion. In the literature, the laparoscopic approach is reported to have advantages in terms of a fast recovery and reduced morbidity (27). Our study suggests that surgeons more often use minimally invasive procedures during PN. Surgeons prefer a more open approach during RN and for small early-stage masses. The surgical approach in the RN cohort was dictated mainly by the size and complexity of the tumor. Our study also demonstrated significantly greater blood loss with an open approach in both the PN and RN cohorts. However, there was no significant difference in the transfusion rate between the open and laparoscopic approaches in either group. In agreement with our findings, a meta-analysis reported that laparoscopic RN resulted in less blood loss and lower transfusion rates than open RN (blood loss: WMD =−201.02, 95% CI: −246.29 to−155.75, blood transfusion rate: OR =0.59, 95% CI: 0.43-0.81) (28).
Our study’s limitations are the retrospective, nonrandomized study design and the possible presence of unidentified confounding variables. Another significant limitation was the performance of procedures by multiple surgeons in six different centers, as the individual learning curve and experience of each surgeon could be sources of bias. Additionally, the lack of nephrometry scores is another limitation; nomogram data have only recently been collected. The patients were treated over a long span of time, and it remains uncertain whether the changes in patient selection and quality of medical care influenced the results. Furthermore, in this study, all participants were followed according to the respective institutional protocols, and there was a lack of standardization of follow-up.