Colorectal Carcinoma
54 COLORECTAL CARCINOMA
Kathleen Liscum M.D.
1. What are the top three causes of cancer deaths in the United States?
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Lung, breast or prostate, and colon cancer.
2. List a few of the presenting symptoms of patients with colorectal cancer.
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Intermittent rectal bleeding, vague abdominal pain, fatigue secondary to anemia, change in bowel habits, constipation, tenesmus, and perineal pain.
3. What options are available to evaluate a patient who has guaiac-positive stools?
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To evaluate the entire colon and rectum, one may perform a barium enema and proctoscopy or a colonoscopy. Colonoscopy is 10 times more expensive but is more sensitive for lesions < 1 cm.
4. List at least five risk factors for colorectal cancer.
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Prior adenomatous polyps, family history of colorectal cancer, age older than 40 years, chronic ulcerative colitis, Crohn’s colitis, history of colon cancer, exposure to pelvic radiation for prostate or cervical cancer, and familial polyposis. Hamartomatous polyps (Peutz-Jeghers syndrome), inflammatory polyps, and hyperplastic polyps are not considered premalignant.
5. What are the current screening recommendations of the American Cancer Society for colorectal cancers?
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A yearly digital rectal examination with testing for occult blood for patients age 40 years and older. Additionally, for patients older than age 50 years, a flexible sigmoidoscopy is recommended every 3-5 years.
6. In what part of the colon or rectum are most cancers found?
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Historically, there has been a higher incidence of cancers in the rectum and left colon. However, over the past 50 years, there has been a gradual shift toward an increased incidence of right colon cancers. This change in pattern may reflect improvement in early detection.
7. Surgical options for colorectal cancer are dependent on the tumor location. What operation should be performed for a patient with a lesion at 25 cm from the anal verge?
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A sigmoid colectomy.
8. What about a lesion at 9 cm from the anal verge? Show answer
A low anterior resection (LAR).
9. What about a lesion at 4 cm from the anal verge? Show answer
An abdominoperineal resection (APR). This requires a permanent colostomy.
10. What is the significance of finding adenomatous polyps in a patient’s colon?
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KEY POINTS: COLORECTAL CARCINOMA
1. Presenting symptoms may include intermittent rectal bleeding, vague abdominal pain, fatigue secondary to anemia, change in bowel habits, constipation, tenesmus, and perineal pain.
2. The current recommendations of the American Cancer Society for screening are a yearly digital rectal exam with testing for occult blood at age 40 years and for patients over 50 a flexible sigmoidoscopy every 3-5 years.
3. Patients with lymph node involvement should receive chemotherapy postoperatively to treat micrometastases.
This patient is six times more likely to develop colorectal cancer than a patient without polyps. Evidence suggests that all colon cancers arise from adenomatous polyps. The “adenoma-carcinoma sequence” describes this transformational process. Patients with familial adenomatous polyposis (FAP) typically harbor more than 100 polyps, which cover the colonic mucosa. If these patients go untreated, they will, without exception, develop adenocarcinoma of the colon by age 40 years.
11. How does the surgeon prepare the patient’s colon for an operation?
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Bowel preparation includes both a mechanical cleansing and appropriate antimicrobial prophylaxis. This combination has resulted in significant decrease in morbidity and mortality from colon surgery. Mechanical cleansing can be accomplished by lavage with polyethylene glycol (Go-Lytely) or a combination of cathartics and enemas (Fleet’s Prep).
Antimicrobial prophylaxis should cover the expected aerobic and anaerobic flora of the gut. Significant controversy exits over whether the antibiotics should be given enterally (e.g., neomycin, 1 g, and metronidazole [Flagyl], 1 g, three times orally at 4-hour intervals the evening before surgery) or parenterally (e.g., cefotetan, 2 g intravenously within 1 hour before surgery). Many clinicians give both to obtain both intraluminal and systemic protection.
12. What is Dukes’ staging system?
Dukes A – Tumor confined to bowel wall
Dukes B – Tumor invading through the bowel wall
Dukes C – Tumor cells found in the regional lymph nodes
In 1932, Dr. Dukes described a staging system for rectal cancer. He originally described the following: Since his original article was published, this classification has been modified several times. One of the most commonly used modifications is the inclusion of Dukes’ D stage, which indicates distant metastases.
13. Which patients with colorectal cancer require adjuvant (postoperative) therapy?
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Patients with lymph node involvement (Dukes’ C) should receive chemotherapy postoperatively to treat micrometastases. Two large studies have documented a survival advantage for these patients. However, no studies have documented a survival advantage for patients with Dukes’ B disease treated with chemotherapy.
Patients with rectal cancer with a significant chance of local recurrence (Dukes’ B and C) should be treated with radiation therapy. This may be given preoperatively, postoperatively, or with a combined “sandwich” technique.
References
WEB SITE
http://www.nejm.org
BIBLIOGRAPHY
1. Colorectal Cancer Collaborative Group: Adjuvant radiotherapy for rectal cancer: A systematic overview of 22 randomised trials involving 8507 patients. Lancet 358:1291-1304, 2001.
2. Jass JR: Pathogenesis of colorectal cancer. Surg Clin North Am 82:891-904, 2002. Medline Similar articles
3. Levin B, Brooks D, Smith RA, Stone A: Emerging technologies in screening for colorectal cancer: CT colonography, immunochemical fecal occult blood tests, and stool screening using molecular markers. CA Cancer J Clin 53:44-55, 2003. Medline Similar articles
4. Lynch HT, de la Chapelle A: Hereditary colorectal cancer. N Engl J Med 348:919-932, 2003. Medline Similar articles
5. National Institutes of Health Consensus Conference: Adjuvant therapy for patients with colon and rectal cancer. JAMA 264:1444-1450, 1990.
6. Ransohoff DF: Screening colonoscopy in balance issues of implementation. Gastroenterol Clin North Am 31:1031-1044, 2002. Medline Similar articles
7. Salz LB, Minsky B: Adjuvant therapy of cancers of the colon and rectum. Surg Clin North Am 82:1035-1058, 2002.
8. US Multisociety Task Force on Colorectal Cancer: Colorectal cancer screening and surveillance: Clinical guidelines and rationale-update based on new evidence. Gastroenterology 124:544-560, 2003.
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Abernathy’s Surgical Secrets, Updated Edition (Book w / Student Consult)
Author / s: Harken Alden H., Abernathy Charles, Moore Ernest Eugene
Year: 2004
Pages: 473
Publishers: Elsevier Mosby; 5th Bk & Acc edition
ISBN: 0323034160
