SUMMARY
Microsatellite instability constitutes an important oncogenic molecular pathway in colon cancer (12–15%). Microsatellite instability is a molecular marker of deficient DNA mismatch repair (MMR), which occurs from somatic hypermethylation of the MLH1 promoter or less frequently as a result of germline mutations in MMR genes. The excellent prognosis of patients with stage II deficient MMR colon cancer today, makes this information mandatory in order to decide or not on adjuvant chemotherapy. MMR deficiency may also predict tumor chemoresistance to 5-fluorouracil adjuvant treatment. However, when looking at very recent data on 5-fluorouracil plus oxaliplatin-based adjuvant regimens, it seems that the benefit of this adjuvant therapy is similar between deficient and proficient MMR patients.
Financial & competing interests disclosure
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.
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