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Table 4 Comparison of the learning curve phases: RTME versus LTME

From: Comparison of the operative outcomes and learning curves between laparoscopic and “Micro Hand S” robot-assisted total mesorectal excision for rectal cancer: a retrospective study

  Phase 1 (n = 51) Phase 2 (n = 54)
RTME (n = 17) LTME (n = 34) p value RTME (n = 23) LTME (n = 31) p value
Age (year) 56.2 ± 9.5 60.1 ± 10.1 0.189 58.3 ± 9.6 60.3 ± 11.7 0.500
Male 8 (47.1) 16 (47.1) 1.000 12 (52.2) 15 (48.4) 0.783
BMI (kg/m2) 21.8 ± 2.9 22.8 ± 4.7 0.414 21.8 ± 3.0 21.5 ± 3.5 0.735
ASA (I/II/III) 6/9/2 (35.3/52.9/11.8) 13/15/6 (38.2/44.1/17.7) 0.793 13/7/3 (56.5/30.4/13.1) 10/13/8 (32.3/41.9/25.8) 0.187
Distance from AV (cm) 8.1 ± 3.1 7.6 ± 3.2 0.588 8.3 ± 2.9 7.5 ± 3.4 0.375
CRT 1 (5.9) 3 (8.8) 1.000 4 (17.4)) 2 (6.5) 0.384
Procedure type    1.000    1.000
LAR 16 (94.1) 32 (94.1)   22 (95.7) 29 (93.5)  
APR 1 (5.9) 2 (5.9)   1 (4.3) 2 (6.5)  
Operative time (min) 360.6 ± 40.8 338.1 ± 47.2 0.100 323.5 ± 42.6 301.9 ± 52.8 0.114
Blood loss (ml) 148.2 ± 73.8 195.0 ± 62.4 0.022 135.4 ± 65.4 180.3 ± 83.5 0.037
Conversion 1 (5.9) 2 (5.9) 1.000 0 1 (3.2) 1.000
Protective ileostomy 11 (64.7) 19 (63.3) 0.925 11 (47.8) 12 (40.0) 0.569
Hospital stay (day) 9.5 ± 3.7 12.2 ± 3.5 0.017 9.0 ± 4.0 11.6 ± 4.4 0.029
C–D grade (III–V) 1 (5.9) 2 (5.9) 1.000 2 (8.7) 2 (6.5) 1.000
Tumor size (cm) 3.3 ± 1.2 3.5 ± 1.4 0.602 3.5 ± 1.6 4.0 ± 1.6 0.221
Retrieved lymph node 15.2 ± 4.8 16.7 ± 5.7 0.369 15.4 ± 5.0 14.5 ± 4.8 0.485
pTNM (I/II/III) 1/4/12 (5.9/23.5/70.6) 5/7/22 (14.7/20.6/64.7) 0.652 3/7/13 (13.1/30.4/56.5) 8/8/15 (25.8/25.8/48.4) 0.515
DRM (cm) 2.4 ± 1.3 2.7 ± 1.5 0.545 2.4 ± 1.4 2.3 ± 1.5 0.757
Involved DRM 0 0 0 0
Involved CRM 1 (5.9) 0 0.333 1 (4.3) 0 0.426
Quality of TME    0.933    0.858
Complete 12 (70.6) 23 (67.6)   19 (82.6) 25 (80.6)  
Nearly complete 4 (23.5) 8 (23.5)   2 (8.7) 4 (12.9)  
Incomplete 1 (5.9) 3 (8.8)   2 (8.7) 2 (6.5)  
  1. BMI body mass index, ASA American Society Anesthesia, AV anal verge, CRT chemoradiation therapy, LAR low anterior resection, APR abdominal perineal resection, DRM distal resection margin, CRM circumferential resection margin, TME total mesorectal excision. Values are presented as mean ± standard deviation or n (%)