Figure 1. Axial T2 MRI image of a 52-year-old male with clinical T2 mass seen on the right kidney with nephrometry score of 10x. Previous medical history: diabetes type 2, hypertension, and chronic kidney disease 3a (estimated glomerular filtration rate 51 mL/min/1.73 m2).

Figure 2. Axial T2 MRI image of a 75-year-old female with clinical T2 mass seen on the left kidney with nephrometry score of 12ph. Previous medical history: diabetes type 2 and hypertension with estimated glomerular filtration rate >60 mL/min/1.73 m2.

Historically, surgical management of renal masses relied on radical nephrectomy (RN), regardless of stage. While the renal system is robust with excellent reserve, living with a solitary kidney poses many health risks. Furthermore, radical nephrectomy performed in specific patient scenarios, such as bilateral tumors, solitary kidneys, and preexisting chronic kidney disease (CKD), can result in significant morbidity and mortality risk. The advent of nephron-sparing surgery with partial nephrectomy (PN) has enabled urologists to enhance functional outcomes for patients with renal tumors, as preservation of healthy renal parenchyma can prevent renal deterioration and delay consequent development of cardiovascular disease.¹

Current guidelines in the US and Europe recommend PN as the preferred approach to the management of T1 renal masses.^2-4 Specifically, AUA guidelines recommend PN for T1a (≤4 cm) masses and the EAU (European Association of Urology) recommends PN for T1 masses (≤7 cm). For T2 renal masses (>7 cm), both AUA and EAU guidelines do not recommend a particular surgical approach, as evidence in this space is lacking to definitively support partial vs radical nephrectomy.

To date, only 1 prospective clinical trial has been conducted that compares PN to RN in regard to oncologic outcomes. In an intention to treat analysis for renal masses <5 cm, Von Poppel et al demonstrate that RN conferred an overall survival (OS) benefit compared to PN with an HR of 1.50 (CI 1.03-2.16, P = .03). There was no significant difference seen in cancer-specific survival (CSS) (HR = 2.06, CI 0.62-6.81, P = .23). The results of this trial were in surprising contrast to prior large retrospective study results. However, the trial also terminated early due to poor patient accrual and therefore is not sufficiently powered to make definitive conclusions.⁵ In a follow-up report on functional outcomes, PN was found to reduce the incidence of mild to moderate CKD compared with RN.⁶

The decision to proceed with PN for T2 renal masses must be weighed with the risk of adverse surgical and oncological outcomes. In a large meta-analysis, Mir et al assessed functional, oncologic, and perioperative outcomes in patients with ≥cT1b tumors undergoing PN vs RN; 23 studies were included, with 5 specifically analyzing outcomes for renal masses ≥T2. Pooled analysis of these 5 studies demonstrated that patients who underwent PN had significantly higher estimated blood loss and incidence of postoperative complications (RR = 2, P < .001) as well as lower rates of recurrence (RR = 0.61, P = .004) and cancer specific mortality (RR = 0.65, P = .03). Of note, the renal mass size of the PN group was on average ∼2 cm smaller than those of the RN group.⁷ In the aforementioned meta-analysis, only 2 of the 5 studies examined outcomes in T2 masses specifically.^8,9 In a cohort of 202 patients, Kopp et al demonstrated equivalent oncologic outcomes between PN and RN for management of clinical T2 masses (5-year CSS of 86.7% and 82.5%, respectively). However, when considering both groups together (RN plus PN), a nephrometry score ≥10 conferred worse progression-free survival, CSS, and OS. In a subsequent analysis of functional outcomes, Kopp et al showed that RN was associated with worse renal deterioration compared to PN in renal masses with a nephrometry score <10. Yet, there was no enhanced renal protection seen in the PN group for nephrometry score ≥10. Taken together, this suggests that more complex tumors are associated with worse oncologic outcomes and lack of functional benefit, regardless of surgical approach.⁸ Klett et al examined a matched cohort of 72 patients who underwent PN (of which 82% had an open approach surgery) to 379 patients who underwent RN for clinical T2 renal masses over a median follow-up time of 7.1 years (IQR 3.6-11.4). None of the patients at the PN group had estimated glomerular filtration rate (eGFR) <45 mL/min/1.73 m² at 3 years, contrastingly, to 23% of the RN patients (P = .03). However, no differences were found regarding metastasis-free survival or CSS between the groups.¹⁰ In a parallel investigation, Bardshaw et al in a multicentric retrospective study assessed the outcomes of 648 patients, of which 216 underwent robot-assisted PN and the remainder underwent minimally invasive RN. The median R.E.N.A.L. (for radius, exophytic/endophytic, nearness of tumor to collecting system, anterior/posterior, location relative to polar line) score was 9 (P = .15), and the median tumor size was 8 cm (P = .56). The PN group had higher incidence of postoperative complications (22% vs 11%, P < .001) and positive surgical margins (8.3% vs 2.6%, P = .001). The functional outcomes were better for PN, where patients in the RN group had higher risk for de novo eGFR <60 mL/min/1.73 m² (HR = 2.35, P < .001) and eGFR <45 mL/min/1.73 m² (HR = 3.85, P < .001). However, the added benefit of functional outcomes in the PN group didn’t translate to a better survival outcome. In a median follow-up time of 34 months, no differences were found in pT2 RCC in 5-year disease-free survival (78.6% for PN and 85.3% for RN, P = .6) and in 5-year OS (76.3% for PN and 88% for RN, P = .22).¹¹

A retrospective study with a long follow-up period performed by Janssen et al compared oncologic outcomes in a small cohort of 18 patients who underwent PN to 105 patients who underwent RN for renal masses larger than 7 cm. The median follow-up time was 102 months. They demonstrated that the PN group compared to the RN group had a significantly longer 10-year CSS (86% compared to 70%, respectively) and 10-year OS (77% and 59%, respectively). Still, given the significant difference in recurrence rate between the groups (40% in the RN group vs 11% in the PN group), these results should be interpreted cautiously.¹²

In Figures 1 and 2, we present cases of 2 distinct patients with clinical T2 masses, both with high R.E.N.A.L. scores. The patient depicted in Figure 1 is a young male concurrently suffering from CKD stage 3a (eGFR = 51 mL/min/1.73 m²). In this patient, RN could adversely impact global glomerular function. Despite the heightened risk of short-term morbidity associated with PN, this patient may indeed gain from long-term preservation of eGFR. Conversely, the patient illustrated in Figure 2 is a 75-year-old female with a complex tumor, yet without any coexisting CKD. For her, the incremental short-term morbidity risk associated with PN may not translate into a tangible long-term benefit.

Presently, most of the literature examining the role of PN vs RN for clinical T2 renal masses, as it pertains to functional and oncologic outcomes, is limited to retrospective studies. These studies inevitably suffer from an inherent selection bias. The decision to pursue PN may be affected by surgeon preference and experience, patient risk factors (age, preexisting CKD, functional status, etc) and tumor characteristics (Figures 1 and 2). Currently, there are no prospective clinical trials that carefully examine the role of performing nephron-sparing surgery for large tumors compared with RN. As a result, careful patient selection and shared decision-making are imperative when performing PN for T2 renal masses.