The more recent COlorectal cancer Laparoscopic or Open Resection II (COLOR II) Study Group trial was designed to address the laparoscopic learning curve that may have skewed results in the UK MRC CLASICC trial in favor of the open group. In this study, 1103 patients with rectal cancer within 15 cm of the anal verge were randomized to laparoscopic (n = 739) and open (n = 364) groups. Macroscopic resection “completeness,” and circumferential and distal resection margins were the same in both groups. The laparoscopic group had less blood loss, shorter time to bowel movements, shorter time to tolerating liquids, and shorter hospital LOS [5]. The UK MRC CLASICC trial required investigators to have performed 20 cases prior to study entry. Recent evidence suggests that the laparoscopic learning curve may be closer to 50–75 cases [91]. Some of the advantages for laparoscopy com­pared to open in the UK MRC CLASICC study—less blood loss, decreased postop­erative pain, and shorter hospital LOS—were also advantages in the COLOR II trial [92]. In addition, the COLOR II trial demonstrated that laparoscopic circumferen­tial margins were as good as open surgery (10 % vs. 10 %) and better for low rectal cancers. However, the complete TME rate was 4 % lower in the laparoscopic group compared to the open group (88 % vs. 92 %). The prominent laparoscopic expertise of the COLOR II trial compared to the UK MRC CLASICC trial did not eliminate long operative times – average was 240 min with a range of 180–300 min. And though conversion to open decreased from 29 % in the UK MRC CLASICC trial to 17 % in the COLOR II trial, this is still significantly higher than conversion with robotic surgery for rectal cancer (0–10.0 %) [86, 89, 90].

II trial that is designed to randomize 146 patients with rectal cancer within 9 cm of the anal verge to laparoscopic and robotic arms. The primary endpoint is TME qual­ity. Secondary outcomes include 30-day perioperative complications, sexual and uri­nary function, quality of life, anorectal function, and 3-year disease- free survival. The estimated study completion date for the primary outcome is December 2014 [95]. The second trial is the COLRAR study at Kyungpook National University in South Korea. This trial was designed to prospectively randomize 540 patients to lapa­roscopic and robotic arms for TME for low and mid rectal cancers within 10 cm of the anal verge. Surgeons must have performed 50 lap and 50 robotic cases to be eli­gible for participation. The primary outcome is surgical quality via pathologic exami­nation. Photo and video documentation was performed for each case. Secondary outcomes include 3- and 5-year disease-free and overall survival, pelvic autonomic nerve preservation, short-term morbidity, lymph node harvest, local recurrence, and surgical blood loss. The estimated study completion date is December 2015 [96].

surgeons beyond their learning curves may proceed to more challenging cases that take longer and be more likely to convert to open. These authors suggest that future studies should employ a multidimensional assessment of technical skills thought to be indicators of satisfactory outcomes, such as the 3-phase CUSUM model, to eval­uate robotic learning curves in the clinical setting [100, 101].