cT1a Renal Masses Less Than 2 versus 2 cm or Greater Managed by Robotic Partial Nephrectomy: A Propensity Score Matched Comparison of Perioperative Outcomes

Purpose: We performed a single center evaluation to compare perioperative, pathological and functional outcomes of robotic partial nephrectomy of T1a renal masses less than vs greater than 2 cm. Materials and Methods: Propensity score 1:1 matching of queried patients was performed using the institutional robotic partial nephrectomy database from January 2007 to January 2017. Matching was done by patient age, gender, race, body mass index, the Charlson comorbidity index, smoking status, diabetes, hypertension, hyperlipidemia, ASA (R) (American Society of Anesthesiologists (R)) score, estimated glomerular filtration rate, chronic kidney disease stage and R.E.N.A.L. (radius, exophytic/endophytic properties, nearness of tumor to collecting system or sinus, anterior/posterior, location relative to polar line and abutting main renal artery or vein) score. We analyzed the records of 524 patients, including 262 with a renal mass less than 2 cm vs 262 with a renal mass 2 cm or greater. Perioperative, pathological and functional outcomes were evaluated. Results: Smaller renal masses (less than 2 cm) were associated with significantly lower operative time, blood loss, ischemia time (mean +/- SD 14.3 +/- 9.58 vs 21.5 +/- 9.51 minutes, p < 0.001) and intraoperative transfusions (0% vs 2.7%, p = 0.015). Moreover, we found superior early renal functional outcomes as assessed by the estimated glomerular filtration rate on postoperative day 1 (mean 83.1 +/- 21.3 vs 76.6 +/- 22.0 mg/ml/1.73 m(2), p = 0.001), greater parenchymal preservation (mean 89.9% +/- 9.45% vs 83.6% +/- 8.20%, p < 0.001) and a trend toward a lower rate of postoperative complications (13.5% vs 19.5%, p = 0.080). A higher incidence of malignancy was found in larger tumors (85.9% vs 74.8%, p = 0.002) but no difference was recorded in positive surgical margins. Conclusions: Robotic partial nephrectomy tends to be a low morbidity treatment modality for renal masses less than 2 cm. Although active surveillance is a common option for such tumors, robotic partial nephrectomy remains an alternative in select patients.