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Page 6 of 11 Sawada et al. Mini-invasive Surg 2021;5:6 I http://dx.doi.org/10.20517/2574-1225.2020.100

Figure 1. Distribution of the propensity scores. Before PSM (left) and after PSM (right). PSM: propensity score matching; OPN: open
partial nephrectomy; RAPN: robot-assisted partial nephrectomy.

Table 2. Comparison of perioperative outcomes between patients treated with RAPN and those treated with OPN after propensity
score matching for clinical characteristics
Variables OPN (n = 58) RAPN (n = 58) P value
EBL (mL) < 0.001
Median (IQR) 160 (90-300) 10 (0-60)
Operative time (min) 0.003
Median (IQR) 232 (200-260) 258 (223-297)
Renal artery clamping, n (%) 0.31
Main artery clamping 55 (94.8) 57 (98.3)
Zero ischemia 3 (5.2) 1 (1.7)
Ischemia time (min) < 0.001
Median (IQR) 34 (26-44) 23 (18-28)
Cold ischemia time 27 (21-36) 0
Transfusion, n (%) (including autologous blood 4 (6.9) 1 (1.7) 0.17
transfusions)
Hospital stay, days < 0.001
Median (IQR) 12 (9-14) 7 (7-9)
Conversion to radical nephrectomy, n (%) 2 (3.5) 2 (3.5) 1.0
Overall postoperative complications, n (%) 11 (19.0) 8 (13.8) 0.64
Clavien–Dindo complication ≤ 2 8 (13.8) 3 (5.2) 0.11
Clavien–Dindo complication ≥ 3 3 (5.2) 5 (8.6) 0.46
EBL: estimated blood losses, IQR: interquartile range; OPN: open partial nephrectomy; RAPN: robot-assisted partial nephrectomy.

oncological outcomes of RAPN and OPN for the treatment of highly complex renal tumors of 279 cases.
Their results indicated that RAPN presents a safe and effective alternative to OPN for highly complex renal
tumors, with advantages of reduced blood loss, shorter ischemia time, and shorter length of hospital stay.
Other original studies comparing RAPN with OPN have reported that the advantages of RAPN include
lower rates of complications [8,22-24] . Although, there are many retrospective studies comparing OPN and
RAPN, few have compared these surgical approaches in a single-institutional setting using PSM. Because
our study analyzed RAPN and OPN from a single institution and matched the patients’ backgrounds and
tumor complexities using PSM, we believe that our results provide a higher level of evidence. In fact, the
use of PSM for all preoperative factors, including the RENAL score, in both groups, which are thought
to play important roles in determining the indications and outcomes of RAPN and OPN, resulted in no
significant differences between the two groups.