Chapter 38B. Perspective on Colonic Neoplasms

Colon tumors remain one of the more common reasons for abdominal surgery. Adenocarcinoma of the colon is still the most common histology requiring operative intervention. Other types of malignant tumors and benign lesions make up a distinct minority of colonic neoplastic indications for operation.

The etiology of colorectal cancer remains elusive. Dietary factors, including macro- and micronutrients, have maintained a central importance in theories of the etiology of colon cancer. High dietary fiber, once felt to be protective, has more recently been demonstrated in a large prospective study to not prevent colorectal cancer.1 Conversely, the breakdown products of cooked meat have clearly been implicated in the development of colorectal cancer.2 Because rigid control of the constituents of diet over time is highly unlikely and even strict vegetarians have developed colorectal cancer, it is not likely that lifelong dietary manipulation will substantially alter the natural history of this disease.

Screening for colorectal cancer is clearly effective in reducing the overall mortality from colorectal cancer, presumably by discovery of tumors at an earlier and thus more curable stage. In this respect, it is an ideal disease for directed screening, because the precancerous phase is long and removal of the precancerous lesion is preventive of cancer. The incidence of colorectal cancer has been in a slow decline over the past 10–15 years, due in part to increased application of screening programs in the population as a whole.3

Because of noncompliance of the American population with Hemoccult testing programs or, in fact, any other procedures that require interacting with stool (such as stool DNA analysis), intermittent anatomic evaluation of the entire colon and rectum by some means has become the preferred manner of colorectal cancer screening. Practically, total colonoscopy has become the most common screening procedure, beginning at age 50 in normal-risk individuals. Alternatively, flexible sigmoidoscopy and air contrast barium enema are recommended at 5-year intervals; they are perceived by patients and primary care physicians to be more uncomfortable because of the lack of conscious sedation when compared to colonoscopy.

Radiographic screening with three-dimensional software for interpretation of cross-sectional images is popularly known as “virtual colonoscopy,” a misnomer leading to misunderstandings about the procedure. Individuals undergoing computed tomographic (CT) colonography must mechanically cleanse the colon and then have air (or carbon dioxide) insufflation prior to imaging. Positive findings necessitate referral for optical colonoscopy. There are certain circumstances in which diagnostic CT imaging is indicated; comorbidities that preclude conscious sedation, refusal on the part of the patient to undergo colonoscopy or prior failed attempt(s) and obstruction preventing proximal passage of the instrument are all reasonable indications for CT colonography.

It must be stressed that no method of screening is infallible. Furthermore, there are some individuals who do not have any identifiable factors that would indicate surveillance at an earlier age or with greater frequency who develop colorectal cancer.

Among identifiable risk factors suggesting the need for surveillance beginning at an earlier age than 50 years, family history of cancer is the most common and arguably the most significant factor. Identification of individuals at risk for genetic syndromes begins with accurate history taking from the patient as well as construction of the family pedigree. In the current era of “endoscopy-on-demand” programs, the responsibility for identifying patients and families who would potentially benefit from genetic screening and more aggressive endoscopic surveillance shifts to the primary caregivers and ancillary personnel, because the endoscopists often do not know the patient or participate in the decision to perform endoscopy.

Ultimately, the genetics of all colorectal cancers will be elucidated, perhaps resulting in the development of reliable blood testing to replace screening tests that are expensive, resource intensive, and have some associated risk. At present, the variations of familial adenomatous polyposis (FAP) with mutations of the APC gene as well as the multiple mismatch repair (MMR) genes involved in the basic phenotype of hereditary nonpolyposis colon cancer (HNPCC) represent a minority of all colon cancer patients. Attenuated FAP, a mutation of the APC gene, exhibits a different phenotype than classic FAP characterized by fewer polyps and later age of onset. More recently, the recessive MYH genes, with an attenuated FAP phenotype but a different genetic transmission, have been added to the better-known genetic syndromes.4 As more of the genetic associations are elucidated, the molecular basis of sporadic colorectal cancers will become evident.

Preoperative localization of colonic neoplasms should be a priority in order to plan operative strategy. In some instances, colonoscopy to the cecum, traversing the lesion to exclude the presence of synchronous pathology that requires coincident attention, is not possible. In the elective situation, other strategies may be employed to visualize the proximal colon. Water-soluble contrast enema may be able to outline the colon above a lesion that does not allow the passage of a colonoscope; this requires communication with the radiologist to avoid excessive pressure and overinflation of the colon with a risk of perforation. As mentioned previously, CT colonography may be used to visualize the colon but has the limitation of not being able to cleanse the colon because of the obstruction. In the instances in which complete colonic evaluation is not accomplished preoperatively, the performance of intraoperative colonoscopy using carbon dioxide rather than air for insufflation to minimize the duration of colonic distention has been suggested. This requires on-table lavage to allow detailed mucosal inspection and is probably impractical in many instances of operation for obstruction. As a result, individuals undergoing urgent operation precluding preoperative colonic inspection should be evaluated by colonoscopy sooner in the postoperative period with the expectation that there will be discovery of the occasional synchronous neoplasm.

Preoperative marking of tumor location by the colonoscopist, most often by submucosal injection of India Ink, has become quite popular; this has been driven primarily by the relative loss of tactile sensory capability for the surgeon with the advent of laparoscopic colon resection. It is not unusual for the endoscopist to misinterpret the position of the tip and thus the tumor, leading in some instances to resection of the wrong segment of colon. This is obviated by India Ink marking.

Mechanical cleansing of the colon has recently been deemphasized as a necessary part of the routine preparation of a patient for colon resection.5 While there is no evidence to support an increased risk of anastomotic or infectious complications for elective colon resections in stool-filled bowel, some find this situation aesthetically unpleasing and prefer a colon without formed stool upon which to work. In fact, patients have often had some form of amended bowel cleaning by not eating solids for a day or more, taking some laxative and/or using a disposable enema. This is particularly true for left-sided lesions.

In some instances, the degree of obstruction of the colon is such that preoperative preparation of the colon is not possible. Under these circumstances the options are to (1) perform a subtotal colectomy with anastomosis of the ileum to the colon distal to the lesion; (2) resect the lesion and perform on-table lavage with primary anastomosis; and (3) perform a staged procedure with resection and stoma. A more recent option is the placement by the endoscopist of an expandable metallic stent to relieve the acute obstruction and allow mechanical cleansing of the colon followed by an elective resection in the near future.6

Since the introduction of laparoscopic colon resection in the early 1990s, there has been a relative explosion of this technology. Data from the American Board of Colon and Rectal Surgery reflected utilization of laparoscopy for colon surgery beginning with resident case logs in 1994.7 By continuing to record and analyze resident case lists from colorectal training programs, the percentage of abdominal colorectal resections performed laparoscopically increased from 3.6% in 1994 to 24.3% in 2005.8 Analysis of the relative penetration of pathology indicating operation suggests that the application of laparoscopy for cancer somewhat awaited the publication of the multi-institutional trials outlined in Chap. 37. This fundamental change in the approach to colon surgery represents an enormous challenge for the education of residents and practicing surgeons alike.

Laparoscopic surgery represents an alternative means of accomplishing well-established operative procedures. These new skills must be incorporated into the new curriculum of teaching and learning technical surgery. Fortunately, laparoscopic skills lend themselves to the use of simulation technologies that have been designed, validated, and implemented. The Fundamentals of Laparoscopic Surgery (FLS) program, developed by the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES), is a combination of a didactic curriculum combined with skill assessment using box trainers, trained observers, and validated end points for evaluation of distinct psychomotor and cognitive skills necessary for basic laparoscopy.9 All general surgery residents must have successfully completed the FLS program by graduation from residency. By extension, because all colon and rectal residents are fully trained general surgeons, they will also be FLS-certified.

Computer-based simulation is developing at a rapid pace and may well evolve into procedure-specific training devices. Credentialing of practicing surgeons will probably incorporate simulation exercises for competency determination in the future; perhaps there will also be review of videotapes of specific procedures by hospital credentialing committees or even the surgical boards for both primary certification and part IV of maintenance of certification.

As abdominal access shifts increasingly to laparoscopy, open surgical skills will atrophy, if they are developed at all, during general surgical residency. Volumes of some procedures are already a challenge, pushing many general surgery graduates into subspecialty training after completion of a standard 5-year residency program. Furthermore, the learning curve differs among individual surgeons; marketing pressures and financial incentives may push marginally capable surgeons to do procedures for which they are not yet prepared for safe independent performance.

The growth of laparoscopy has not all been fueled by randomized prospective data demonstrating its superiority over open surgery. Proposed advantages such as shorter length of stay, less postoperative pain and more rapid return to work must be counterbalanced by longer operative times and greater procedural expense. Some of the enthusiasm among patients and referring physicians is stimulated and amplified by misunderstandings of the true benefits of the ‘minimally invasive' approach. There are absolute and relative contraindications to performance of laparoscopic resection outlined in Table 37-3. These criteria must be scrupulously applied to patients seeking laparoscopic surgery.

As a general rule, the same procedural endpoints must be able to be accomplished by laparoscopic techniques; nowhere is this more evident than with cancer surgery. Oncologic results of laparoscopic colon resection for cancer must at least equal those obtained by traditional open surgery. Adequacy of mesenteric lymph node resection has gained considerable traction as a surrogate for quality surgery. Survival is dependent on numbers of lymph nodes harvested, with survival increasing with more resected nodes.10 Numbers of nodes removed are a quality measure in addition to the time-honored outcomes of overall cure and disease-free survival.

Technical horizons awaiting scientific scrutiny are robotics as applied to colorectal surgery, single-port access surgery, and NOTES (natural orifice transluminal endoscopic surgery). While each of these techniques may find a place in the future, at present they must all be considered experimental in nature. Development of these expensive technologies should not be at the primary direction of market-driven forces; rather, there should be a concerted effort to develop and test new techniques, with at least proof of equivalence, before allowing them to permeate practice.