Predictors and clinical outcomes of renal tumor upstaging from cT1 to pT3a disease in patients who underwent robot-assisted partial nephrectomy.

558 Background: Robot-assisted partial nephrectomy (RAPN) is the standard treatment of small renal masses, offering favorable perioperative, oncological, and functional outcomes. Nevertheless, there remains a risk of kidney cancer upstaging that may influence oncological outcomes. This study evaluates the incidence, risk factors, and clinical outcomes of RAPN patients who were upstaged from cT1 to pT3a. Methods: A retrospective review of a prospectively maintained, IRB-approved database was reviewed to identify all cases of cT1 renal mass managed with RAPN between 2006 and 2023. Risk factors for cT1/pT3a upstaging were analyzed with logistic regression analyses, and overall and recurrence-free survival outcomes with Kaplan-Meier analysis. Results: Of the 1414 patients with cT1 renal masses, 134 (9.4%) were upstaged to pT3a. Upstaged patients were older (median 64.6 vs. 60 years, p=0.011), had higher comorbidity burden (CCI 2 vs. 1, p<0.001), greater tumor complexity (RENAL 8 vs. 6, p<0.001), and more frequent positive margins (17.2% vs. 5.3%, p<0.001). On multivariable analysis, larger tumor size (OR 1.14; 95% CI 1.05–1.27, p=0.005) and hilar location (OR 1.36; 95% CI 1.02–1.81, p=0.036) independently predicted upstaging. At median follow-up of 38 months, recurrence was more frequent in upstaged patients (3.8% vs. 1.8%, p=0.19). Conclusions: In patients with cT1 renal mass undergoing RAPN, upstaging to pT3a disease represents an uncommon event. Despite the low incidence, cT1/pT3a upstaging may translate to worse oncological outcomes, including positive surgical margins and a higher risk of disease recurrence. When considering the risk factors, both larger tumor diameter and hilar locations have emerged as independent predictors of pathology upstaging to pT3a. Baseline clinicodemographic and outcomes of all included patients. Upstaging( n = 134) No Upstaging( n = 1280) p Age (years) 64.6 (54.8 – 70.1) 60 (51.8 – 68) 0.01 BMI (kg/m 2 ) 31.2 (26.7 – 35.9) 29.9 (26.3 – 34.9) 0.25 Gender (Male) 87 (64.9%) 809 (63.2%) 0.76 CCI 2 (0 – 4) 1 (0 – 3) <0.001 Smoking History 71 (53.4%) 622 (48.6%) 0.51 Baseline GFR (mL/min/1.73m 2 ) 77.4 (62.2 – 96.3) 80.1 (65.8 – 95.4) 0.14 RENAL Score 8 (6 – 9) 6 (5 – 8) <0.001 Low Complexity 46 (37.7%) 624 (54.1%) Intermediate Complexity 56 (45.9%) 445 (38.6%) High Complexity 20 (16.4%) 84 (7.3%) Largest Tumor Diameter (cm) 4 (3 – 4.8) 3 (2.2 – 4) <0.001 Positive Surgical Margin 21 (17.2%) 59 (5.3%) <0.001 Follow-up duration (months) 31 (17 – 62) 40 (19 – 66) 0.69 <jats:td colspan="1" co