Adjuvant therapy for colon cancer.

Adjuvant therapy for colon cancer is now a mature and widely accepted standard of care for patients with resected large bowel tumors: adjuvant therapy for stage III colon cancer has also been shown to be highly cost-effective. The cost of 5-FU/levamisole therapy for stage III colon cancer per year of life saved is less than $ 5,000, which represents a favorable cost-benefit relationship for a medical intervention. The clinician managing a patient with colon cancer at the present time has several options for therapy. In patients with stage III colon cancer, therapy with 5-FU-based regimens clearly increases overall and disease-free survival. It is also clear that the results that have been obtained are not perfect; therefore, the first option of therapy should always be an ongoing clinical trial. Many such trials are available, and Table 7 lists currently active studies in the United States. The clinician managing a patient with stage III colon cancer who is not in a clinical trial may choose a variety of regimens administered for durations of 6 to 12 months (Table 8). The preponderance of evidence suggests that 5-FU plus levamisole for 12 months is equal in efficacy to 5-FU plus leucovorin-based regimens given for a shorter period of time. A clinician may still choose the 5-FU plus levamisole regimen because of the decreased oral, myelosuppressive, and diarrheal toxicities associated with that regimen as opposed to the 5-FU/leucovorin regimens. Portal vein infusion of fluorinated pyrimidines still must be considered investigational. Finally, although we cannot be absolutely sure about the benefit of adjuvant therapy in patients with resected node-negative colon cancer, the NSABP data suggest that some benefit may be seen in these patients. It is known that patients with stage II cancers demonstrating high-grade bowel obstruction or bowel perforation have poor prognoses with surgery alone. Such patients may be good candidates for adjuvant therapy. Also, a major effort to define high risk and low risk for recurrence in patients with stage II colon cancer by analyzing molecular genetic factors (tumor ploidy and alternations in tumor suppressor genes) may lead to a selection of Dukes B patients definitely requiring adjuvant therapy.