Defective DNA mismatch repair (MMR) occurs in approximately 15% of sporadic colorectal cancers. Studies have shown that patients with MMR-deficient colorectal cancers have a more favorable prognosis, but evidence indicates these patients do not benefit from adjuvant 5 fluorouracil-based chemotherapy. The importance of determining MMR status to inform clinical decision-making for adjuvant chemotherapy in patients with stage II colon cancer is discussed.
