Adjuvant 5-Fluorouracil Chemotherapy for CIMP-Positive Colorectal Cancers

Adjuvant 5-fluorouracil (5-FU)-based chemotherapy is commonly administered to patients with stage III (lymph node–positive) colorectal cancers (CRCs). Multiple studies have shown that microsatellite instability (MSI) in CRCs is associated with failure to benefit from 5-FU. Most MSI tumors result from hypermethylation of the MLH1 gene. Widespread gene inactivation by promoter hypermethylation is referred to as the CpG island methylator phenotype (CIMP), which includes a group of tumors that are microsatellite stable. Whether CIMP in both MSI and microsatellite stable CIMP tumors is associated with failure to benefit from adjuvant 5-FU chemotherapy is unclear.

To investigate this issue, researchers followed a population-based cohort of 302 pat…