Perioperative outcomes after Robot-assisted partial nephrectomy for very small (≤ 2 cm) versus larger small (> 2-4 cm) renal tumors: a multi-institutional propensity score-matched study.

The detection of incidentally identified small renal masses has increased, prompting greater use of nephron-sparing procedures. Robot-assisted partial nephrectomy (RAPN) is established for tumors ≤ 4 cm; however, evidence directly comparing its use for very small tumors (≤ 2 cm) and slightly larger lesions (> 2-4 cm) is limited, particularly in Asian populations. We evaluated how tumor size affects perioperative outcomes, renal function preservation, and oncological safety in RAPN. The data of 649 Japanese patients who underwent RAPN for clinically localized renal cell carcinoma were retrospectively analyzed. Patients were grouped according to maximal tumor diameter (≤ 2 cm or > 2-4 cm). Propensity score matching was performed to mitigate disparities in patient backgrounds including tumor complexity and location. Outcomes assessed included operative and console times, warm ischemia time, estimated blood loss (EBL), postoperative complications, trifecta and pentafecta achievement, renal functional preservation, and recurrence-free survival (RFS). After matching, 193 patient pairs were included. Tumors ≤ 2 cm were associated with significantly shorter operative and console times, lower warm ischemia, reduced EBL, fewer major complications, and higher trifecta achievement, compared with tumors > 2-4 cm. Renal function preservation was comparable between groups. Oncological outcomes were excellent in both cohorts, with 5-year RFS of 98.2% and 98.0% for tumors ≤ 2 cm and > 2-4 cm, respectively. RAPN for tumors ≤ 2 cm offers superior perioperative outcomes without compromising oncological control, compared with that for tumors > 2-4 cm. These findings support RAPN as a safe and effective nephron-sparing approach for managing incidentally detected sub-2 cm renal tumors.