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Table 5 Comparison of the learning curve phases: Phase 1 versus Phase 2

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

  RTME (n = 40) LTME (n = 65)
Phase 1 (n = 17) Phase 2 (n = 23) p value Phase 1 (n = 34) Phase 2 (n = 31) p value
Age (year) 56.2 ± 9.5 58.3 ± 9.6 0.500 60.9 ± 10.0 60.3 ± 11.7 0.941
Male 8 (47.1) 12 (52.2) 0.749 16 (47.1) 15 (48.4) 0.915
BMI (kg/m2) 21.8 ± 2.9 21.8 ± 3.0 0.962 22.8 ± 4.7 21.5 ± 3.5 0.217
ASA (I/II/III) 6/9/2 (35.3/52.9/11.8) 13/7/3 (56.5/30.4/13.1) 0.337 13/15/6 (38.2/44.1/17.7) 10/13/8 (32.3/41.9/25.8) 0.711
Distance from AV (cm) 8.1 ± 3.1 8.3 ± 2.9 0.856 7.6 ± 3.2 7.5 ± 3.4 0.897
CRT 1 (5.9) 4 (23.0) 0.373 3 (8.8) 2 (6.5) 1.000
Procedure type    1.000    1.000
LAR 16 (94.1) 22 (95.7)   32 (94.1) 29 (93.5)  
APR 1 (5.9) 1 (4.3)   2 (5.9) 2 (6.5)  
Operative time (min) 360.6 ± 40.8 323.5 ± 42.6 0.009 338.1 ± 47.2 301.9 ± 52.8 0.005
Blood loss (ml) 148.2 ± 73.8 135.4 ± 65.4 0.566 195.0 ± 62.4 180.3 ± 83.5 0.422
Conversion 1 (5.9) 0 0.425 2 (5.9) 1 (3.2) 1.000
Protective ileostomy 11 (64.7) 11 (47.8) 0.289 19 (63.3) 12 (40.0) 0.071
Hospital stay (day) 9.5 ± 3.7 9.0 ± 4.0 0.644 12.2 ± 3.5 11.6 ± 4.3 0.544
C–D grade (III–V) 1 (5.9) 2 (8.7) 1.000 2 (5.9) 2 (6.5) 1.000
Tumor size (cm) 3.3 ± 1.2 3.5 ± 1.6 0.707 3.5 ± 1.4 4.0 ± 1.6 0.166
Retrieved lymph node 15.2 ± 4.8 15.4 ± 5.0 0.892 16.7 ± 5.7 14.5 ± 4.8 0.099
pTNM (I/II/III) 1/4/12 (5.9/23.5/70.6) 3/7/13 (13.1/30.4/56.5) 0.613 5/7/22 (14.7/20.6/64.7) 8/8/15 (25.8/25.8/48.4) 0.377
DRM (cm) 2.4 ± 1.3 2.4 ± 1.4 0.964 2.7 ± 1.5 2.3 ± 1.5 0.346
Involved DRM 0 0 0 0
Involved CRM 1 (5.9) 1 (4.3) 1.000 0 0
Quality of TME    0.423    0.477
Complete 12 (70.6) 19 (82.6)   23 (67.6) 25 (80.6)  
Nearly complete 4 (23.5) 2 (8.7)   8 (23.5) 4 (12.9)  
Incomplete 1 (5.9) 2 (8.7)   3 (8.8) 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 (%)