Initially described in 2004,26 pilot series (≤25 patients) demonstrated that a robotic approach to PN was technically feasible in select masses with acceptable peri-operative outcomes, including estimated blood loss (EBL), WIT, and hospital length of stay (HLOS).27-31 These findings have been confirmed by larger institutional series18, 32-34 and have been extended to more complex tumors.14, 16, 18, 19, 35
However, while the safety of RPN has been confirmed, relative advantages with RPN when compared to LPN are unproven,8, 22, 29, 36-41 and reported clinical outcomes are difficult to interpret in the setting of significant selection bias and lack of stratification by anatomic complexity.
Several scoring systems have been described in an attempt to reproducibly stratify renal masses by anatomic characteristics and facilitate the objective comparison of varying renal lesions, and include P.A.D.U.A.,42 C-index,43 and the R.E.N.A.L. Nephrometry score (NS).44 The first such system described and the most rigorously evaluated is the R.E.N.A.L. nephrometry score, which has been utilized to predict tumor histology and grade45as well as decision making for the small renal mass.46 Categorization by nephrometric complexity has been associated with intraoperative parameters such as ischemia time, EBL, and hospital length of stay in patients undergoing LPN,47 and rates of major urologic complications stratified by Clavien classification undergoing PN.48
In a large single institution series (N=281) comparing OPN and RPN for intermediate (NS 7-9) and complex (NS 10-12) renal tumors, Simhan et al reported that for moderately complex tumors, RPN was associated with an increased operative duration (205.9 vs. 189.5 min, p=0.02), but was also associated with decreased EBL (131.3 vs. 256.5cc, p<0.01) and hospital length of stay (3.7 vs. 5.6 days, p<0.001) when compared to the OPN group.49 Similarly, comparison of highly complex lesions revealed a reduced LOS in the RPN group (2.9 vs. 6.1 days, p<0.001).
Operative and Clinical Outcomes
Across published series, mean operative time (82.7 to 279 min),27, 28 estimated blood loss (92-329 cc),22, 50 and hospital length of stay37, 41 (2.0-6.2 days) varied widely, which can be attributed to data reported at differing points on institutional learning curves. In the largest single institution series to date (100 patients, 107 lesions) Scoll et al34 reported mean OR time, estimated EBL, and HLOS of 206 min, 127 cc, and 3.2 days respectively, which compares favorably with historic LPN series.3 Comparative data have proved to be conflicting, and to date has failed to show clear trends favoring RPN over LPN. Seven such series reported no significant differences in intra-operative variables, which may be attributable to small sample sizes.22, 27, 29, 37-39, 41
In a single institution comparative series of 102 consecutive cases undergoing LPN and RPN, Wang et al reported significant reductions in OR time (140 vs. 156 min, p=0.04) and HLOS (2.5 vs. 2.9 days, p=0.03) in the RPN group, while there was no difference in EBL (136 vs. 173 mL) between groups.36 In a large multi-institutional series comparing 118 LPN and 129 RPN patients by three experienced surgeons over a five-year period, Benway et al reported no significant difference in OR time (189 vs. 174 min) between groups, while a reduced EBL (155 vs. 196 cc, p=0.03) and shorter hospital length of stay (2.4 vs. 2.7 days, p<0.001) were noted in the RPN group.8 In the only comparison of RPN and OPN using standardized criteria, Simhan et al reported significant trends towards reduced EBL in moderately complex tumors and reduced HLOS in all patients undergoing RPN (described above).49
Again, it is important to consider that these series represent comparisons of LPN or OPN by experienced surgeons and RPN at the beginning of their respective learning curves, which likely influences these outcomes of interest.
Intra-operative and peri-operative complication rates for RPN have generally been low and comparable to historical LPN series. Early series demonstrated high rates of conversion to open, laparoscopic, or hand-assisted procedures (up to 20%),27 likely reflecting surgeon experience at the beginning of their learning curve.9
In fact, in large series the rate of conversion is roughly 1%,51 and some authors have proposed that surgeons who embark upon RPN should have the necessary skills to undock the robot and proceed laparoscopically if a device malfunction or injury occurs so that the benefits of a minimally invasive approach can be retained.22
Although these early reports are limited by lack of standardized complications nomenclature, overall complication rates in larger series of RPN range from 14%-25% 17, 18, 34-36 and are comparable with LPN in direct comparative series (8.6% vs. 10.6%).8, 39 Recent evidence has demonstrated that tumor characteristics influence complication rates following partial nephrectomy,48 and future efforts must strive to account for anatomic complexity when comparing operative outcomes.