Figure 2. Top: Prevalence of a reverse transcriptase–polymerase chain reaction (RT-PCR) positive test (%) in patients with colorectal cancer before and at intervals after surgery (number of positive patients and total patients studied in each group are shown within each bar). There was a significant decrease (P = 10⁻⁴) in the prevalence of RT-PCR positivity result at 24 hours after surgery, but no additional change at up to 12 weeks after surgery. Bottom: Prevalence of an RT-PCR positive test (%) in patients with colorectal cancer before and at intervals after surgery. A significant decrease compared with the preoperative RT-PCR prevalence was seen at 24 hours after “curative” resection of node-negative tumors (Dukes A and B) but not node-positive ones (Dukes C). Numbers in parentheses represent number of patients available for blood sampling at each time point.