General Information

Note: Estimated new cases and deaths from colon cancer in the United States in 2005:[1]

• New cases: 104,950.
• Deaths (colon and rectal cancers combined): 56,290.

Note: Some citations in the text of this section are followed by a level of evidence. The PDQ editorial boards use a formal ranking system to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. (Refer to the PDQ summary on Levels of Evidence for more information.)

Cancer of the colon is a highly treatable and often curable disease when localized to the bowel. Surgery is the primary form of treatment and results in cure in approximately 50% of patients. Recurrence following surgery is a major problem and is often the ultimate cause of death.

The prognosis of patients with colon cancer is clearly related to the degree of penetration of the tumor through the bowel wall, the presence or absence of nodal involvement, and the presence or absence of distant metastases. These 3 characteristics form the basis for all staging systems developed for this disease. Bowel obstruction and bowel perforation are indicators of poor prognosis.[2] Elevated pretreatment serum levels of carcinoembryonic antigen (CEA) have a negative prognostic significance.[3]

Many other prognostic markers have been evaluated retrospectively for patients with colon cancer, although most, including allelic loss of chromosome 18q or thymidylate synthase expression, have not been prospectively validated.[4-13] Microsatellite instability, also associated with hereditary nonpolyposis colon cancer (HNPCC), has been shown to be associated with improved survival independent of tumor stage in a population-based series of 607 patients younger than 50 years with colorectal cancer.[14] Treatment decisions depend on factors such as physician and patient preferences and the stage of the disease rather than the age of the patient.[15-17] Racial differences in overall survival after adjuvant therapy have been observed, without differences in disease-free survival, suggesting that comorbid conditions play a role in survival outcome in different patient populations.[18]

Because of the frequency of the disease, ability to identify high-risk groups, demonstrated slow growth of primary lesions, better survival of patients with early-stage lesions, and relative simplicity and accuracy of screening tests, screening for colon cancer should be a part of routine care for all adults starting at age 50 years, especially for those with first-degree relatives with colorectal cancer. Groups that have a high incidence of colorectal cancer include those with hereditary conditions, such as familial polyposis, HNPCC or Lynch syndrome variants I and II, and ulcerative colitis.[19] Together they account for 10% to 15% of colorectal cancers. Patients with HNPCC reportedly have better prognoses in stage-stratified survival analysis than patients with sporadic colorectal cancer, but the retrospective nature of the studies and possibility of selection factors make this observation difficult to interpret.[20] [Level of evidence: 3iiiA] More common conditions with an increased risk include a personal history of colorectal cancer or adenomas; first-degree family history of colorectal cancer or adenomas; and a personal history of ovarian, endometrial, or breast cancer.[21,22] These high-risk groups account for only 23% of all colorectal cancers. Limiting screening or early cancer detection to only these high-risk groups would miss the majority of colorectal cancers.[23] (Refer to the PDQ summaries on Screening for Colorectal Cancer and Prevention of Colorectal Cancer for more information.)

Following treatment of colon cancer, periodic evaluations may lead to the earlier identification and management of recurrent disease.[24-27] The impact of such monitoring on overall mortality of patients with recurrent colon cancer, however, is limited by the relatively small proportion of patients in whom localized, potentially curable metastases are found. To date, no large-scale randomized trials have documented the efficacy of a standard, postoperative monitoring program.[28-32] CEA is a serum glycoprotein frequently used in the management of patients with colon cancer. A review of the use of this tumor marker suggests the following:[33]

• A CEA level is not a valuable screening test for colorectal cancer due to the large numbers of false-positive and false-negative reports.
• Postoperative CEA testing should be restricted to patients who would be candidates for resection of liver or lung metastases.
• Routine use of CEA levels alone for monitoring response to treatment should not be recommended.

The optimal regimen and frequency of follow-up examinations are not well defined, however, because the impact on patient survival is not clear and the quality of data is poor.[30-32] New surveillance methods, including CEA immunoscintigraphy [34] and positron emission tomography,[35] are under clinical evaluation.

Gastrointestinal stromal tumors can occur in the colon. (Refer to the PDQ summary on Adult Soft Tissue Sarcoma Treatment for more information.)

References

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2. Steinberg SM, Barkin JS, Kaplan RS, et al.: Prognostic indicators of colon tumors. The Gastrointestinal Tumor Study Group experience. Cancer 57 (9): 1866-70, 1986.  [PUBMED Abstract]
   
3. Filella X, Molina R, Grau JJ, et al.: Prognostic value of CA 19.9 levels in colorectal cancer. Ann Surg 216 (1): 55-9, 1992.  [PUBMED Abstract]
   
4. McLeod HL, Murray GI: Tumour markers of prognosis in colorectal cancer. Br J Cancer 79 (2): 191-203, 1999.  [PUBMED Abstract]
   
5. Jen J, Kim H, Piantadosi S, et al.: Allelic loss of chromosome 18q and prognosis in colorectal cancer. N Engl J Med 331 (4): 213-21, 1994.  [PUBMED Abstract]
   
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20. Watson P, Lin KM, Rodriguez-Bigas MA, et al.: Colorectal carcinoma survival among hereditary nonpolyposis colorectal carcinoma family members. Cancer 83 (2): 259-66, 1998.  [PUBMED Abstract]
    
21. Ransohoff DF, Lang CA: Screening for colorectal cancer. N Engl J Med 325 (1): 37-41, 1991.  [PUBMED Abstract]
    
22. Fuchs CS, Giovannucci EL, Colditz GA, et al.: A prospective study of family history and the risk of colorectal cancer. N Engl J Med 331 (25): 1669-74, 1994.  [PUBMED Abstract]
    
23. Winawer SJ: Screening for colorectal cancer. Cancer: Principles and Practice of Oncology Updates 2(1): 1-16, 1987. 
    
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33. Clinical practice guidelines for the use of tumor markers in breast and colorectal cancer. Adopted on May 17, 1996 by the American Society of Clinical Oncology. J Clin Oncol 14 (10): 2843-77, 1996.  [PUBMED Abstract]
    
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