These clinical findings align with in vitro experimental results, which demonstrate increased resistance of MSI CRC cells to fluorouracil.23 In fact, a competent MMR system is crucial for the efficacy of fluorouracil because MMR proteins promote DNA damage-induced apoptosis.24 Therefore, it has been suggested that CRC patients with dMMR should not undergo adjuvant fluorouracil therapy. This evidence concerns the gene MRC1 and colorectal carcinoma.