Introduction
Surgical resection is the primary curative treatment for patients with localized colorectal cancer. The most accurate prognostic indicator of colon cancer is its stage at diagnosis, and in patients with locally advanced disease, chemotherapy has a role in decreasing the risk for recurrence or metastasis.
Staging of colorectal cancer is based on the depth of penetration of the tumor into the bowel wall, the involvement of regional lymph nodes, the involvement of adjacent organs, and the presence or absence of distant metastasis. Surgery performed according to oncologic principles is designed to resect the cancer with clear margins, provide the most accurate staging possible, and preserve function. The purpose of this chapter is to describe these surgical techniques as applied to cancer of the colon.
Epidemiology
Colorectal cancer is the third most frequently diagnosed cancer in men and women and the second leading cause of cancer death in the United States. In 2013, there were an estimated 102,480 new cases of colon cancer and 40,340 new cases of rectal cancer, with an estimated 5830 deaths from colon and rectal cancers combined. However, mortality from colorectal cancer has decreased by almost 35% from 1990 to 2007, likely because of earlier diagnosis through screening and improvements in management.
Prognostic Factors
Oncologic outcomes of colon cancer resection include survival and recurrence. Survival is usually reported as overall survival including deaths from all causes, or age-adjusted survival, controlling for deaths from causes unrelated to the colon cancer. Recurrence is classified as local recurrence, distant recurrence or metastasis, or both. The most important prognostic factor after resection for colon cancer is the stage of disease at presentation. Survival is usually reported by stage, according to the American Joint Committee on Cancer staging system, as follows: stage I: overall survival is well above 90%; stage II: overall survival is 65% to 90%; stage III: overall survival 45% to 75%; and stage IV: overall survival is 10% to 20%. For patients with high-risk stage II and stage III disease, adjuvant chemotherapy can reduce the risk of recurrence and improve survival. Adjuvant 5-fluorouracil (5-FU) and leucovorin (LV) provides an approximately 25% to 30% relative risk reduction for recurrence and approximately 10% absolute improvement in survival at 8 years. Capecitabine is an oral fluoropyrimidine and has been shown to be equivalent to 5-FU/LV in patients with stage III colon cancer. The addition of oxaliplatin to 5-FU/LV also improves risk for recurrence and survival with an approximately 20% incremental risk reduction for recurrence among stage III patients when compared with 5-FU alone. The role of radiation therapy for colon cancer is limited by the potential for radiation-induced injury to adjacent structures such as the small intestine. Other prognostic factors include the tumor-related complications of obstruction or perforation and histologic features such as signet ring cells, high tumor grade (poor differentiation), and vascular, lymphatic, or perineural invasion.
Preoperative Evaluation
Preoperative assessment of the patient with colon cancer should include staging, an assessment of operative risk, and a thorough family history that documents colorectal cancer and extracolonic cancers associated with syndromes of inherited colorectal cancer. The overall physiologic status of the patient is assessed with preoperative laboratory studies such as a complete blood cell count, urinalysis, chemistry panel, electrocardiogram, and chest radiograph. Nutritional status is assessed clinically. Scoring systems that combine physical activity, symptoms, and laboratory results to assess perioperative risk have been described, including that of the American Society of Anesthesiologists and the Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) and the Portsmouth (p)-POSSUM scores.
A complete staging workup includes a total colonoscopy with biopsy (with consideration given to immunohistochemistry to detect mismatch repair gene expression and/or microsatellite instability testing to detect mismatch repair dysfunction that might suggest Lynch syndrome), carcinoembryonic antigen (CEA), and baseline computed tomography (CT) scans of the chest, abdomen, and pelvis. If questionable abnormalities are seen on the CT or magnetic resonance imaging (MRI) scan, a positron emission tomography/CT scan may be considered to further delineate the abnormality, particularly if more definitive information will change management.
Accurate localization of the tumor is important, especially if the cancer is small and the operation will be performed using the laparoscopic technique. Ideally, the referring colonoscopist has tattooed the colon near the tumor. An accurate family history and the results of preoperative tumor immunohistochemistry/microsatellite instability testing are important in deciding the extent of the resection.
Preoperative Preparation
The role of mechanical bowel preparation remains controversial; however, most surgeons continue to recommend bowel preparation prior to a routine colectomy. One potential benefit is to decrease the weight and distension of the colon for minimally invasive mobilization. The use of prophylactic oral antibiotics during mechanical preparation is also controversial. A recent evaluation of 24 hospitals in the Michigan Surgical Quality Collaborative Colectomy Best Practices Study showed that mechanical preparation was used in 86% of patients and that the addition of oral antibiotics reduced the risk for surgical site infections (4.5% vs 11.8%, P = .0001) and the risk for prolonged ileus (3.9% vs 8.6%, P = .011) without increasing the risk for Clostridium difficile colitis. Evidence consistently supports the use of intravenous antibiotics prior to making an incision to reduce the rate of wound infections.
Prophylaxis against deep venous thrombosis should be performed prior to the induction of anesthesia and may include subcutaneous heparin or one of the low molecular weight heparin agents. In addition, graded lower extremity compression stockings and sequential pneumatic compression devices also should be applied intraoperatively and their use should be continued postoperatively until the patient is walking.
Operative Principles and Techniques
Surgery is the primary treatment of localized colon cancer and in many cases will be the only treatment that is necessary. The surgical principles for resectable, nonmetastatic colon cancer include colectomy with complete, en bloc removal of regional lymph nodes following the principles of oncologic resection. These principles are:
- 1.
Resection of the cancer-containing bowel and the wedge of mesentery associated with the arterial supply of the affected segment, including the regional lymph nodes
- 2.
Ligation of the feeding vessel at its origin
- 3.
Removal or biopsy of suspicious lymph nodes that are located outside the field of resection
- 4.
Unresected positive lymph nodes indicate an incomplete resection
- 5.
Minimum proximal and distal resection margins are 5 cm
- 6.
A minimum of 12 mesenteric lymph nodes should be found and examined for accurate staging
No specific margin is recommended for clearance of the terminal ileum for patients with right colon cancer undergoing resection other than that defined by vascular supply because mural spread to the ileum is rare.
Exploration
Whether laparotomy or a minimally invasive technique is chosen, the presence of metastatic disease must be carefully assessed, with particular attention directed to the liver, peritoneal surfaces, and pelvis. In women, the ovaries should be examined not only for metastatic deposits but also for synchronous primary neoplasms. Next, the resectability of the primary tumor should be determined. If the cancer is adherent to an adjacent organ, it should be removed with an en bloc resection.
Surgical Treatment of Right Colon Cancer
Our preferred approach to colon resection is laparoscopic. A number of variations for the placement of the ports and the sequence of the steps for vascular dissection and bowel mobilization have been described; our preferred port placement is shown in Figure 61-1 . This approach optimizes the port placement to be contralateral to the disease. The sequence of dissection (e.g., vascular or bowel first) is at the discretion of the operating surgeon; however, vascular control is facilitated by a medial to lateral approach, which takes advantage of the native attachments of the colon to facilitate exposure of the vascular anatomy. On the other hand, bowel mobilization may be preferred during open surgery, allowing the bowel to be elevated to expose the central vessels.
Cancers that are located in the cecum or the ascending colon should be removed by a right hemicolectomy, which encompasses the bowel served by the ileocolic, right colic, and, as necessary, the right branch of the middle colic vessels ( Fig. 61-2 ). If the lesion is located in the area of the hepatic flexure, the right branch of the middle colic vessels should be routinely divided. An extended right colectomy includes ligation and division of the main middle colic arterial trunk and is performed for any lesion in the transverse colon beyond the hepatic flexure ( Fig. 61-3 ).The splenic flexure may need to be released for a tension-free anastomosis.
A right hemicolectomy should begin by gaining access to the retroperitoneum, which can be accomplished via different approaches. The medial and lateral approaches are most common during laparoscopy. With the medial to lateral approach, the ileocolic pedicle is identified and elevated. The peritoneum on the caudal side of the pedicle is incised and the retroperitoneum is entered. The ileocolic artery and vein are isolated after first clearly identifying their relationship to the superior mesenteric artery and vein. During the course of this dissection, the lymphoadipose tissue overlying the ileocolic vessels should be swept distally and included with the resection specimen. The duodenum should be identified during this maneuver because the ileocolic vessels are elevated away from the duodenum and pancreatic head. The ileocolic artery and vein should be divided at their origins from superior mesenteric vessels ( Fig. 61-4 ). The ileocolic vein typically courses behind the artery before draining into the superior mesenteric vein (SMV), but care should be taken to clearly delineate the anatomy because significant variation may exist. Continuing the dissection along the superior mesenteric artery (SMA) reveals the right colic and middle colic arteries. This maneuver is facilitated by completing the mobilization of the proximal transverse colic mesentery away from the pancreatic head.
Alternatively, the colon can be mobilized from inferior to superior by elevating the cecum and base of small bowel mesentery cephalad. The lateral approach should begin by incising the lateral peritoneal attachments of the colon beginning at the cecum and elevating the colon away from the retroperitoneum. Regardless of how the retroperitoneum is accessed, the principles of the resection remain the same. The right colon mesentery is lifted away from the retroperitoneum, and the duodenum and pancreatic head are identified ( Fig. 61-5 ). The lateral attachments are incised and the hepatic flexure is fully mobilized. In cases of locally advanced tumors, the bowel mobilization should remain widely clear of the tumor to avoid the potential for perforation.
Certain dangers must be avoided for safe and effective mobilization of the right colon.
- 1.
Anatomic variation is found in both the arterial supply and the venous drainage of the right colon. The origin of the right colic artery is quite variable. It may arise from the SMA, the middle colic artery, or the ileocolic artery, or it may be entirely absent. The venous drainage through the right colic vein typically joins the right gastroepiploic vein and/or the pancreaticoduodenal vein to form the gastrocolic trunk of Henle ( Fig. 61-6 ). The right branch of the middle colic vein also may drain into the common trunk.
FIGURE 61-6
Gastrocolic trunk of Henle.
- 2.
The veins in the proximal transverse mesentery are fragile and prone to avulsion, which results in serious bleeding.
- 3.
Care should be taken to avoid injury to the duodenum as the mesentery is mobilized off of the duodenum and the head of the pancreas. Small venous tributaries are present along the edge of the pancreatic head, and dissection in the incorrect plane can lead to bleeding.
- 4.
At the base of the transverse colon mesentery, the SMA and SMV are at risk for injury.
- 5.
Inadvertent mobilization of the duodenum and right kidney and injury to the right ureter or gonadal vein should be avoided. Routine deliberate dissection of the ureter as a means to identify it and protect it from injury is discouraged unless it cannot be seen through the thin veil of retroperitoneal tissue and definitive visualization of the ureter is required. In some cases, the ureter can be identified where it crosses the iliac vessels and it can be followed into the retroperitoneum.
Upon completion of the mobilization, the terminal ileum should be divided approximately 10 cm proximal to the ileocecal valve, protecting its mesentery. The transverse colon is divided according to the location of the tumor. An ileocolic anastomosis can then be performed after confirming adequate blood supply through seeing or feeling pulsatile flow in the marginal vessels, or Doppler interrogation.
Surgical Treatment of Transverse Colon Cancer
The best surgical procedure is determined by the location of the tumor and the need to remove the regional lymphatics. Resection is based on arterial supply and the associated mesentery. Thus a proximal lesion may require resection of the middle colic and ileocolic arteries ( Fig. 61-7 ), whereas several options may be appropriate for a more distal lesion. A cancer in the middle of the transverse colon may be treated by transverse colectomy, including the root of the middle colic artery, although an extended right colectomy with an anastomosis to the proximal descending colon is an alternative option ( Fig. 61-8 ). Tumors located further distally may need to be treated with an extended left colectomy.
