Lecture
Patient will present as → a 65-year-old male with several months of weight loss, vague right upper quadrant pain, and thin-caliber stools. His medical history is notable for 50-pack-years of smoking and obesity. On exam, he appears chronically ill and has firm hepatomegaly. His labs reveal a hemoglobin of 10.7 g/dL and mildly elevated ALT and AST.
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Progression of adenomatous polyp into malignancy (adenocarcinoma) usually occurs within 10-20 years - Colon CA is the third leading cause of cancer death after lung cancer and skin cancer
- Risk factors include age > 45 y/o, inflammatory bowel disease, polyps, low fiber, high animal fat diet, smoking, ETOH
- Presents as painless rectal bleeding and a change in bowel habits
Screening begins at 45 and continues until 75 y/o
- Selectively screen adults aged 76 to 85 years for colorectal cancer:
- There is adequate evidence that the benefits of detection and early intervention decline after age 75 years
- Discuss together with patients the decision to screen, taking into consideration the patient’s overall health status (life expectancy, comorbid conditions), prior screening history, and preferences.
Recommended intervals for colorectal cancer screening tests include:
Stool tests:
- High-sensitivity gFOBT or FIT every year
- sDNA-FIT every 1 to 3 years
CT colonography every 5 years
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- (1 additional individual per 1000 would develop cancer in his or her lifetime due to radiation exposure)
Flexible sigmoidoscopy every 5 years or flexible sigmoidoscopy every 10 years + FIT every year
- (Serious complications occur in approximately 3.4 per 10,000 procedures)
Colonoscopy screening every 10 years
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- Perforation of the colon occurs in an estimated 3.8 per 10,000 procedures
- Serious complications—including perforation, major bleeding, diverticulitis, severe abdominal pain, and cardiovascular events occur in an estimated 25 per 10,000 procedures
USPSTF colorectal cancer screening guidelines
**When adequate screening colonoscopy is accomplished, intercurrent stool tests (i.e., between colonoscopy examinations) are not necessary. In addition, for patients who have had a negative colonoscopy and have been recommended to have routine screening in 10 years, screening with FIT or other screening tests is not indicated prior to the end of the 10-year period.
"Hereditary factors are believed to contribute to up to 30% of colorectal cancers. Relative risk is 3.8 times if the family member's cancer was diagnosed at less than 45 years of age. Recommended screening in a single first-degree relative with colorectal cancer diagnosed before age 60 is beginning colonoscopy at age 40 or ten years younger than the age at diagnosis of the youngest affected first-degree relative. Then if negative, every 5 years."
Treatment is surgical resection and chemotherapy for nodal involvement
- 5FU is mainstay of chemotherapy
- Monitor CEA with treatment
 Osmosis |
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Picmonic
Colorectal cancer
Colorectal cancer is the third most common cancer in both men and women with the majority of cases being adenocarcinoma. Risk factors include a family history of colorectal cancer, personal history of inflammatory bowel diseases such as ulcerative colitis or Crohn’s disease, a diet high in red meat, obesity, alcohol consumption greater than four drinks per week, and cigarette smoking. Clinical manifestations of early-stage colorectal cancer are usually non-specific, while manifestations of late-stage colorectal cancer include hepatomegaly, peritonitis, and abdominal pain. Patients aged 45 and older should undergo a colonoscopy once every 10 years to assess for polyps and/or the presence of cancer.
Play Video + QuizQuestion 1 |
A 48-year-old man comes to your office with a vague lower right-sided abdominal fullness (not pain). He describes to you a general feeling of “not feeling well,” fatigue, and a somewhat tender area “down near my appendix.” He states, “I have no energy. I’m tired all the time.” He also suspects that his skin changed color, first to a pale color and then to slightly yellow.
On direct questioning, he admits to anorexia, weight loss of 30 pounds in 6 months, nausea most of the time, vomiting twice, some diarrhea that seems to be mucus, and blood in the stool almost every day for the past 3 months. When you ask him what he makes of all of this, he tells you, “Maybe a very bad flu.”
On examination, the patient looks very pale. Examination of the abdomen reveals abdominal distention. You record the abdominal girth as a baseline. There is a sensation of “fullness” in the right lower quadrant of the abdomen. This area is also dull to percussion and is slightly tender. There is definite percussion of tympani on both sides of the area of dullness. The liver span is approximately 20 cm. The sclerae are yellow.
What is the definitive diagnostic procedure of choice in this patient?
complete blood count (CBC) Hint: See D for answer | |
fecal occult blood samples Hint: See D for answer | |
air-contrast barium enema Hint: See D for answer | |
colonoscopy |
Question 1 Explanation:
The diagnostic procedure of choice in this patient is a total colonoscopy to confirm a mass lesion, to determine the location of that lesion, and to obtain a biopsy specimen of the lesion if possible.
Question 2 |
What is the most likely diagnosis in this patient?
irritable bowel syndrome | |
lactose intolerance | |
adenocarcinoma of the pancreas | |
adenocarcinoma of the colon |
Question 2 Explanation:
In this patient, the problem list at this point is as follows: (1) a middle-aged man with nonspecific feelings of “ill health”; (2) there is a right lower quadrant mass on physical examination, raising suspicion of carcinoma; (3) the liver is enlarged, possibly indicating metastases; (4) the pale appearance suggests anemia; (5) icterus suggests elevated conjugated bilirubin; and (6) the clinically apparent abdominal distention indicates possible ascites.
With this constellation of symptoms and signs, the working diagnosis is adenocarcinoma of the colon, possibly the cecum, with liver metastases.
Question 3 |
The diagnosis of colorectal cancer is made in this patient. What is the definitive treatment of choice?
total colectomy Hint: See B for explanation | |
surgical removal of the mass | |
removal of the appendix Hint: See B for explanation | |
abdominoperineal resection of the rectum Hint: See B for explanation |
Question 3 Explanation:
The definitive surgical treatment of choice in this patient (if feasible) is resection of the colonic mass. The preliminary location of the lesion based on physical examination is in the area of the cecum. If this proves to be correct, the colonic resection will involve the removal of the area from the vermiform appendix to the junction of the ascending and transverse colons. With the presence of liver metastasis, this procedure is palliative.
Question 4 |
Carcinoma of the colon most commonly originates in which of the following?
an adenomatous polyp | |
an inflammatory polyp Hint: See A for explanation | |
a hyperplastic polyp Hint: See A for explanation | |
a benign lymphoid polyp Hint: See A for explanation |
Question 4 Explanation:
The majority of colonic adenocarcinomas evolve from adenomas. Adenomas are a premalignant lesion; in the large bowel, the sequence is adenoma, dysplasia in the adenomas, and adenocarcinoma.
Question 5 |
Adenomatous polyps are found in approximately what percentage of asymptomatic patients who undergo screening?
5% Hint: See D for explanation | |
10% Hint: See D for explanation | |
15% Hint: See D for explanation | |
25% |
Question 5 Explanation:
Both adenomas and the subsequent evolved adenocarcinomas increase in incidence with age, and the distribution of adenomas and cancer in the bowel is similar. Overall, adenomatous polyps are found in approximately 25% of asymptomatic patients who undergo screening colonoscopy. The age-related prevalence of adenomatous polyps is 30% at age 50 years, 40% at age 60 years, 50% at age 70 years, and 55% at age 80 years.
Question 6 |
Which of the following statements best describes the current evidence for fecal occult blood screening as a measure to reduce the morbidity and mortality from colorectal cancer?
There is good evidence to include stool-based testing in screening asymptomatic patients older than 45 years for colorectal carcinoma | |
There is fair evidence to include stool-based testing in screening asymptomatic patients older than 45 years for colorectal carcinoma | |
There is insufficient evidence to include or to exclude stool-based testing testing as an effective screening test for colorectal cancer in asymptomatic patients older than 45 years | |
None of the above |
Question 6 Explanation:
The current U.S. Preventive Services Task Force recommends colorectal cancer screening for all people aged 45 years or older. Screening reduces mortality. Acceptable screening methods include Stool-based tests, colonoscopy, sigmoidoscopy, and CT colonography. Colonoscopy provides an alternative that will find abnormalities throughout the colon and allows removal of polyps at the same time; however, the major complication rate of 1 in 1000 procedures (under the best of circumstances) and the difficult preparation make many patients concerned about the process. Flexible sigmoidoscopy also provides a clear picture, but only of the distal third of the colon. Stool-based tests include the high-sensitivity guaiac fecal occult blood test (gFOBT), fecal immunochemical test (FIT), and stool DNA test. Both high-sensitivity gFOBT and FIT detect blood in the stool; however, they use different methods. High-sensitivity gFOBT is based on chemical detection of blood, while FIT uses antibodies to detect blood. Stool DNA tests detect DNA biomarkers for cancer in cells shed from the lining of the colon and rectum into stool.
Question 7 |
Which of the following statements regarding carcinoembryonic antigen (CEA) and colorectal cancer is true?
CEA is a cost-effective screening test for colorectal cancer Hint: See B for explanation | |
elevated preoperative CEA levels correlate well with postoperative recurrence rate in colorectal cancer | |
CEA is a sensitive test for colorectal cancer Hint: See B for explanation | |
CEA is a specific test for colorectal cancer Hint: See B for explanation | |
CEA has no value in predicting recurrence in colorectal cancer
Hint: See B for explanation |
Question 7 Explanation:
CEA is a glycoprotein found in the cell membranes of a number of tissues, a number of body fluids, and a number of secretions including urine and feces. It is also found in malignant neoplasms of the colon and rectum. Because some of the CEA antigen enters the bloodstream, it can be detected by the use of a radioimmunoassay technique of serum.
Elevated CEA is not specifically associated with colorectal cancer; abnormally high levels of CEA are also found in patients with other gastrointestinal malignant neoplasms and nongastrointestinal malignant neoplasms. CEA levels are elevated in 70% of patients with an adenocarcinoma of the large bowel, but less than 50% of patients with localized disease are CEA positive. Thus, because of these difficulties with sensitivity and specificity, CEA does not serve as a useful screening procedure, nor is it an accurate diagnostic test for colorectal cancer at a curable stage. However, elevated preoperative CEA levels correlate with postoperative recurrence rate, and failure of CEA to fall to normal levels after resection implies a poor prognosis. CEA is helpful in detecting recurrence after curative surgical resection; if high CEA levels return to normal after operation and then increase progressively during the follow-up period, recurrence of cancer is likely.
There are 7 questions to complete.
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References: Merck Manual · UpToDate