Low anterior resection for rectal cancer

Indications and contraindications for robotic low anterior resection

Given the improved ergonomics associated with a robotic approach for pelvic dissection compared to open and laparoscopic approaches, robotic LAR is ideal for low- and mid-rectal tumors located 1 to 10 cm from the anal verge. In order to perform an LAR, a distal margin ≥1 cm from the tumor is required in order to perform a stapled anastomosis. However, for very low rectal tumors, an intersphincteric resection with a hand-sewn coloanal anastomosis or an abdominoperineal resection can still be performed with a robotic approach. As with laparoscopic surgery, the only absolute contraindication to a robotic LAR is inability to tolerate pneumoperitoneum due to hemodynamic instability or severe cardiac or pulmonary disease. Relative contraindications are extensive peritoneal adhesions from prior abdominal operations, locally advanced tumors requiring en bloc multivisceral resection, pelvic or abdominal metastasis that would be difficult to simultaneously resect with a robotic approach, and limited surgeon experience and comfort with robotic LAR.

Robotic versus open and laparoscopic approaches for low anterior resection

There are currently only a limited number of large randomized controlled trials comparing outcomes by operative approach for rectal cancer, five of which compared laparoscopic and open approaches, and only one of which compared robotic and laparoscopic approaches. In the five trials comparing laparoscopic and open approaches, length of stay was significantly shorter for a laparoscopic approach in two of the trials, ^, and there were no significant differences in postoperative complication rates, local recurrence rates, disease-free survival, or overall survival between the two groups in each of the studies. ^{, , ,} However, operative time was significantly longer for a laparoscopic approach in each of the studies ( P > .05), ^{, , , ,} and of more concern, the Medical Research Council Conventional versus Laparoscopic-Assisted Surgery in Colorectal Cancer (MRC CLASICC) trial demonstrated that a laparoscopic approach was associated with a two-fold increase in the rate of a positive circumferential margin (CRM) (12% vs. 6%), and the Australasian Laparoscopic Cancer of the Rectum (ALaCaRT) and the American College of Surgeons Oncology Group (ACOSOG) Z6051 trials revealed that laparoscopic LAR failed to meet the criteria for noninferiority with respect to a composite oncologic metric consisting of completeness of TME, CRM, and distal resection margin compared to an open approach. ^, While the results of these trials raised concerns regarding oncologic outcomes for laparoscopic LAR, a recent noninferiority meta-analysis that included 14 randomized controlled trials did find that laparoscopic resection was noninferior to an open approach with respect to positive CRMs, incomplete mesorectal excision, and positive distal resection margins. Therefore, a laparoscopic approach does appear safe and most likely equivalent to an open approach for resection of rectal cancer in experienced hands.

Given the concerns for oncologic inferiority for a laparoscopic approach and the increasing adoption of a robotic approach for rectal cancer given improved ergonomics, the Robotic versus Laparoscopic Resection for Rectal Cancer (ROLARR) randomized controlled trial was performed to compare outcomes between robotic and laparoscopic approaches for rectal cancer. The international, multicenter superiority trial recruited 471 patients from 29 institutions between January 2011 and September 2014. The primary study endpoint was conversion to an open approach, and secondary endpoints included perioperative complications, 30-day postoperative mortality, CRM positivity, and bladder and sexual dysfunction. The 40 participating surgeons had to perform at least 30 minimally invasive rectal cancer resections, of which ≥10 had to be conventional laparoscopic and ≥10 had to be robotic resections. While a robotic approach was associated with a lower rate of conversion to open surgery, it did not reach statistical significance (8.1% vs. 12.2%, P = .16). There were no significant differences between a robotic and laparoscopic approach with respect to CRM positivity (5.1% vs. 6.3%, P = .56), 30-day postoperative complication rates (33.1% vs. 31.7%, P = .84), 30-day postoperative mortality rates (0.8% vs. 0.9%, P = N/A due to small number of events), bladder dysfunction ( P = .27), male sexual dysfunction ( P = .75), and female sexual dysfunction ( P = .60). While the trial failed to demonstrate any significant differences in outcomes between a robotic and laparoscopic approach, a minimally invasive robotic approach appears safe and still offers the potential for earlier return of gastrointestinal function and shorter length of stay compared to an open approach.

Preoperative assessment

Following an initial diagnosis of rectal adenocarcinoma, patients should undergo multidisciplinary evaluation by surgery, medical oncology, and radiation oncology. For those who are deemed potential surgical candidates based on comorbidity and functional status following a complete history and physical exam, preoperative work-up should include anorectal exam and proctoscopy to assess the distance from the anal verge to the distal extent of the tumor and the relationship between the tumor and the sphincter complex, total colonoscopy to evaluate for synchronous lesions, serum carcinoembryonic antigen (CEA) level, and magnetic resonance imaging (MRI) of the pelvis with contrast and computed tomography (CT) of the chest, abdomen, and pelvis with contrast to determine the American Joint Committee on Cancer (AJCC) clinical TNM stage. While endoscopic ultrasound of the rectum was often utilized in evaluating tumor depth and nodal status in the past, MRI is now the preferred tumor staging modality as it can accurately predict a threatened CRM, has the ability to assess for tumor deposits and vascular invasion, and is not operator dependent. Furthermore, it allows for pretreatment assessment for lateral pelvic lymph node metastasis which may be as high as 18.1% in patients with T3 or T4 lower rectal cancer. CT of the chest, abdomen, and pelvis should be obtained to evaluate for distant metastatic disease as approximately 6% of patients with rectal cancer will have synchronous lung metastasis and 12% will have synchronous liver metastasis. For suspicious liver lesions that are too small to characterize on CT imaging, MRI of the abdomen with contrast can be useful as it has a higher sensitivity than CT imaging, especially for lesions less than 1 cm. Positron emission tomography (PET)/CT can be utilized if there are equivocal findings on CT imaging but should not be routinely obtained or used as a substitute for initial CT staging scans. ^,

Following the results of several randomized controlled trials, neoadjuvant chemoradiation has become the treatment standard for locally advanced rectal cancer, which is defined as clinical T3-T4b and/or clinical node-positive disease, to improve local recurrence rates. ^, Furthermore, “total neoadjuvant therapy” consisting of either induction systemic therapy for 12 to 16 weeks followed by chemoradiation or initial chemoradiation followed by consolidative chemotherapy have been increasingly used due to higher rates of a complete clinical and/or pathologic response and improved recurrence-free survival compared to standard neoadjuvant chemoradiation and adjuvant systemic therapy. Regardless of the neoadjuvant treatment approach, patients who receive neoadjuvant therapy should be restaged with repeat MRI of the pelvis and CT of the chest, abdomen, and pelvis prior to surgical intervention to assess treatment response, evaluate for technical resectability and a clear CRM, and rule out distant metastatic disease. Furthermore, select patients with an apparent clinical complete response following neoadjuvant therapy, characterized by no palpable tumor on examination, no visible pathology aside from a white scar on flexible sigmoidoscopy, and no evidence of disease on repeat imaging, may avoid radical resection with a “watch and wait” surveillance approach at institutions with such a protocol.