Effect of adding oxaliplatin to adjuvant 5-fluorouracil/leucovorin (5FU/LV) in patients with defective mismatch repair (dMMR) colon cancer stage II and III included in the MOSIAC study.

3524 Background: The MOSAIC study (André T, N Engl J Med, 2004) demonstrated that adding oxaliplatin to adjuvant 5FU and LV improved three-year disease-free survival (DFS) in stage II and III resected CC. Efficacy of FOLFOX4 in pts with dMMR stage III was suggested in a retrospective study (Zaanan A, Ann Oncol 2010). Methods: Of the 2,246 pts included in MOSAIC study, formalin-fixed, paraffin-embedded (FFPE) tissue blocks or slides from 1,019 pts were obtained. Thirty-three samples with insufficient tumor tissue were excluded from this translational study. MMR status was determined by immunohistochemistry (IHC) analysis of the protein products of MLH1, MSH2, PMS2, and MSH6 genes. Results: …