In patients with colon cancer who undergo resection for potential cure, 40% to 60% have advanced locoregional disease and are classified as either stage II or stage III. The role of adjuvant therapy in stage III colon cancer is well defined. The results from the MOSAIC trial (Multicenter International Study of Oxaliplatin/5-Fluorouracil/ Leucovorin in the Adjuvant Treatment of Colon Cancer) and the National Surgical Adjuvant Breast and Bowel Project C-07 trial confirm a definite disease-free survival (DFS) benefit with the addition of oxaliplatin to either infusional or bolus 5-fluorouracil/leucovorin (5-FU/LV). The Xeloda in Adjuvant Colon Cancer Therapy (X-ACT) trial showed capecitabine to be of equivalent clinical benefit to bolus 5-FU/LV. However, adjuvant trials with irinotecan, including Cancer and Leukemia Group B (CALGB 89803), the Pan-European Trial in Adjuvant Colorectal Cancer 3 (PETACC-3), and the French ACCORD trial, have not shown a significant DFS advantage. In contrast, in patients with stage II disease, a small survival benefit of 1% to 5% exists with chemotherapy. Perhaps the analysis of molecular markers in combination with high-risk histopathologic features will help increase patient specificity and identify subsets of patients with stage II colon cancer who will derive a survival benefit with adjuvant therapy. The current Intergroup study stratifying stage II patients based on presence of microsatellite instability and loss of heterozygosity 18q allele will help us better understand the risk versus benefit observed.
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