These three characteristics form the basis for all staging systems developed for this disease.
Other prognostic factors include the following:
- Bowel obstruction and bowel perforation are indicators of poor prognosis.
- Elevated pretreatment serum levels of carcinoembryonic antigen (CEA) have a negative prognostic significance.
Many other prognostic markers have been evaluated retrospectively for patients with colon cancer, though most, including allelic loss of chromosome 18q or thymidylate synthase expression, have not been prospectively validated.[9,10,11,12,13,14,15,16,17,18] Microsatellite instability, also associated with HNPCC, has been associated with improved survival independent of tumor stage in a population-based series of 607 patients younger than 50 years with colorectal cancer. 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.
Treatment decisions depend on factors such as physician and patient preferences and the stage of the disease, rather than the age of the patient.[21,22,23]
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.
Following treatment of colon cancer, periodic evaluations may lead to the earlier identification and management of recurrent disease.[25,26,27,28] 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.[29,30,31,32,33]
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:
- A CEA level is not a valuable screening test for colorectal cancer because of 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.