Documenting the natural history of patients with resected stage II adenocarcinoma of the colon after random assignment to adjuvant treatment with edrecolomab or observation: Results from CALGB 9581

Purpose: We conducted a randomized trial comparing adjuvant treatment with edrecolomab versus observation in patients with resected, low-risk, stage II colon cancer. This study also prospectively studied patient- and tumor-specific markers of treatment outcome. Patients and Methods: After surgical resection, patients with stage II colon cancer were randomly assigned to either five infusions of edrecolomab at 28-day intervals or observation without adjuvant therapy. Results: Final accrual included 1,738 patients; 865 patients received edrecolomab, and 873 patients were observed without adjuvant treatment. Median follow-up time was 7.9 years. There were no significant outcome differences between study arms (overall survival [OS], P = .71; disease-free survival, P = .64). The combined 5-year all-cause OS was 0.86 (95% CI, 0.84 to 0.88), and the combined 5-year disease-specific OS was 0.93 (95% CI, 0.91 to 0.94). The relationships between demographic and histopathologic factors and survival differed for all-cause and disease-specific survival outcomes, but no combined prognostic factor model was found to adequately classify patients at higher risk of recurrence or death as a result of colon cancer. Conclusion: Edrecolomab did not prolong survival. Consequently, this large study with a long duration of follow-up provided unique data concerning the natural history of resected stage II colon cancer. Prognostic factors identified in previous retrospective and pooled analyses were associated with survival outcomes in this stage II patient cohort. Results from ongoing molecular marker studies may enhance our ability to determine the risk profile of these patients.