Perioperative and functional outcomes of robot-assisted partial nephrectomy for renal tumors >4 cm in a multi-institutional, multinational cohort

INTRODUCTION & OBJECTIVES: Previous literature has shown size of renal tumors, based on preoperative imaging, to be an important determinant of perioperative and functional outcomes following robot-assisted partial nephrectomy (RAPN). We compared the outcomes of tumors >4 cm with that of <4 cm in a multi-institutional cohort of patients undergoing RAPN. MATERIALS & METHODS: Using the Vattikuti Collaborative Quality Initiative (VCQI) database, 1,114 patients undergoing RAPN between 2006 and 2013 at ten centers across six countries were stratified by clinical T stage (cT1a for <4 cm vs. >cT1b for >4 cm tumors on preoperative imaging). Patient demographic and tumor characteristics were recorded. Multivariate logistic and linear regression models were fitted to analyze the impact of surgical volume on the perioperative and functional outcomes, after controlling for baseline patient/tumor characteristics. RESULTS: There were no significant differences in the baseline characteristics between patients with tumor size <4 cm (828, 74.3%) and >4 cm (281, 25.7%), except for higher Age-adjusted Charlson co-morbidity index and high nephrometry risk score (8.4% vs. 26.2%) tumors in the latter. Patients with tumor >4 cm in size had a greater estimated blood loss (EBL), longer warm ischemia time (WIT) and greater proportion of post-operative complications were seen in tumors >4 cm (Table 1). No statistically significant difference was noted for surgical margins, length of stay, intra-operative complications, or % change in creatinine at 6-month follow-up between cT1a and >cT1b tumors. However, on multiple linear regression analyses, higher clinical stage was a significant predictor of greater EBL (B=71.9, 95% CI=39.4- 104.4, p<0.001) and WIT (B=1.3, 95% CI=0.1-2.5, p=0.04), but not post-operative complications.