Colon cancer has traditionally been treated surgically. However, many cases of colon cancer are systemic at the time of diagnosis, and apparently curative surgery is followed at a later date by tumor recurrence as a consequence of circulating tumor cells before the surgery. Adjuvant medical therapies are designed to prevent recurrences after surgical resection. The current standard for clinical prognostication relies principally on pathological staging. In early-stage colon cancers (stages I and II), all the tumor is contained within the wall of the colon. Less than 10% of patients with stage I disease have a recurrence, and adjuvant chemotherapy is . . .