Carcinoma of the colon
From Medical-Wiki
The third most common cancer in both men and women is colorectal cancer. Most of these tumors are adenocarcinoma. The disease has a definite genetic character. It is also related to inflammatory bowel disease, hereditary polyposis, diets rich in fat and cholesterol, nonpolyposis syndromes. Combined, colon and rectal cancer will annually account for roughly 60,000 deaths.
Adenocarcinoma of the colon develops from polyps that arise from normal mucosa. The disease is surgically preventable.
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Clinical presentation
Typically, this cancer is discovered by screening and may have been entirely asymptomatic up to that point. Of those who are symptomatic, roughly half present complaining of abdominal pain, 35% with altered bowel habits, and 15% with intestinal obstruction. As a rule, right-sided lesions tend to be large and more likely to bleed. Left-sided tumors tend to be small and more likely to obstruct.
Missed tumors
The rate of missed tumors varies between men and women and between right and left sided lesions. The reasons for these differences remain obscure. [1]
Diagnosis
Physical findings
Physical examination may be completely normal. This is particularly true early on in the disease’s progress. As the disease progresses, weight loss, cachexia, pain, and abdominal tenderness may be present. Occult fecal blood is present in 30% of patients from the outset of their cancer. Very late in the disease, patients may exhibit ascites and a palpable abdominal mass. [2]
Screening
Because colorectal cancer follows a predictable pattern, and because resection of polyps in early stages of the disease will prevent the development of cancer, there has been extensive attention given to screening for this disease. Like all screening procedures, the key is finding an appropriate compromise between the risk of not screening and the risk inherent in the screening itself. (Having colonoscopy done on a monthly basis would almost eliminate a person’s chances of getting cancer of the colon. It would, however, precipitously increase the possibility of that person dying from a perforated colon and sepsis.)
Patient stratification
In 2007, guidelines as released by the national Guidelines Clearinghouse, called for patients to be stratified according to three factors:
- Has the patient had colorectal cancer or an adenomatous polyp?
- Does the patient have an illness (e.g., inflammatory bowel disease) that predisposes him or her to colorectal cancer?
- Has a family member had colorectal cancer or an adenomatous polyp? If so, how many, was it a first-degree relative (parent, sibling, or child), and at what age was the cancer or polyp first diagnosed?
If a patient answers no to all three questions, then the patient is said to be of average risk.
Screening options
Recommendations for people of average risk are that they be given the following options. (The reason that there are options instead of a rigid protocol is that in 1997, studies showed there does not appear to be a statistical advantage of one screening regimen over another.) If the patient fell into the at-risk category, the options are modified.
Fecal Occult Blood Testing
Offer yearly screening with fecal occult blood test (FOBT) using a guaiac-based test with dietary restriction or an immunochemical test without dietary restriction. Two samples from each of 3 consecutive stools should be examined without rehydration. Patients with a positive test on any specimen should be followed up with colonoscopy.
Sigmoidoscopy
Offer flexible sigmoidoscopy every 5 years.
Combined FOBT and Flexible Sigmoidoscopy
Offer screening with FOBT every year combined with flexible sigmoidoscopy every 5 years. When both tests are performed, the FOBT should be done first.
Colonoscopy
Offer colonoscopy every 10 years.
Double-Contrast Barium Enema
Offer double-contrast barium enema (DCBE) every 5 years. [3]
Guidelines for at risk populations
People With a Family History of Colorectal Cancer or Adenomatous Polyps People with a first-degree relative (parent, sibling, or child) with colon cancer or adenomatous polyps diagnosed at age <60 years or 2 first-degree relatives diagnosed with colorectal cancer at any age should be advised to have screening colonoscopy starting at age 40 years or 10 years younger than the earliest diagnosis in their family, whichever comes first, and repeated every 5 years (see Table 3 in the original guideline document). People with a first-degree relative with colon cancer or adenomatous polyp diagnosed at age >60 years or 2 second-degree relatives with colorectal cancer should be advised to be screened as average risk persons, but beginning at age 40 years. People with 1 second-degree relative (grandparent, aunt, or uncle) or third-degree relative (great-grandparent or cousin) with colorectal cancer should be advised to be screened as average risk persons.
Familial Adenomatous Polyposis People who have a genetic diagnosis of familial adenomatous polyposis (FAP), or are at risk of having FAP but genetic testing has not been performed or is not feasible, should have annual sigmoidoscopy, beginning at age 10-12 years, to determine if they are expressing the genetic abnormality. Genetic testing should be considered in patients with FAP who have relatives at risk. Genetic counseling should guide genetic testing and considerations of colectomy.
Hereditary Nonpolyposis Colorectal Cancer People with a genetic or clinical diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC) or who are at increased risk for HNPCC should have colonoscopy every 1-2 years beginning at age 20-25 years, or 10 years earlier than the youngest age of colon cancer diagnosis in the family--whichever comes first. Genetic testing for HNPCC should be offered to first-degree relatives of persons with a known inherited mismatch repair (MMR) gene mutation. It should also be offered when the family mutation is not already known, but 1 of the first 3 of the modified Bethesda Criteria is met (see Table 5 in the original guideline document).
Surveillance of People at Increased Risk
People with a History of Adenomatous Polyps Patients who have had 1 or more adenomatous polyps removed at colonoscopy should be managed according to the findings on that colonoscopy. Patients who have had numerous adenomas, a malignant adenoma (with invasive cancer), a large sessile adenoma, or an incomplete colonoscopy should have a short interval follow-up colonoscopy based on clinical judgment. Patients who have advanced or multiple adenomas (>3) should have their first follow-up colonoscopy in 3 years. Patients who have 1 or 2 small (<1 cm) tubular adenomas should have their first follow-up colonoscopy at 5 years. It is not unreasonable, given available evidence, to choose even longer intervals. However, the evidence is still evolving. Future evidence may clarify the intervals more precisely. The timing of the subsequent colonoscopy should depend on the pathology and number of adenomas detected at follow-up colonoscopy. For example, if the first follow-up colonoscopy is normal or only 1 or 2 small (<1 cm) tubular adenomas are found, the next colonoscopy can be in 5 years.
People With a History of Colorectal Cancer Patients with a colon cancer that has been resected with curative intent should have a colonoscopy around the time of initial diagnosis to rule out synchronous neoplasms. If the colon is obstructed preoperatively, colonoscopy can be performed approximately 6 months after surgery. If this or a complete preoperative examination is normal, subsequent colonoscopy should be offered after 3 years, and then, if normal, every 5 years.
People With Inflammatory Bowel Disease In patients with long-standing, extensive inflammatory bowel disease, surveillance colonoscopy with systematic biopsies should be considered. This applies to both ulcerative colitis and Crohn’s colitis because the cancer risk is similar in both diseases. [4]
Treatment guidelines
Guidelines for the treatment of colorectal cancer are also defined—and redefined at regular intervals, depending upon advances in the treatment regimens. [5]
Recent developments
One of the factors that continues to evolve is the efficacy of new screening techniques and the effectiveness of those already being used. There has been considerable attention given to “virtual colonoscopy” and whether it plays a role in normal screening. The general consensus of opinion as of 2007 is that it did not, nor did any other screening techniques other than those captioned in the guidelines noted above.
Concerns about the increase in numbers of colon perforations have been raised, but it does not appear that the rate of perforation has increased. The absolute number of colonoscopy caused perforations has increased simply as a reflection of an increase in the number of procedures being performed.
