Abstract
Differences in tumor characteristics might partially account for mortality disparities between African American (AA) and European American (EA) colorectal cancer patients. We evaluated effect modification by race for exposure and patient-outcomes associations with colorectal tumor methylation among 218 AA and 267 EA colorectal cancer cases from the population-based North Carolina Colon Cancer Study. Tumor methylation was assessed in CACNA1G, MLH1, NEUROG1, RUNX3, and SOCS1. We used logistic regression to assess whether associations between several lifestyle factors-intake of fruits, vegetables, folate, and non-steroidal anti-inflammatory drugs-and tumor methylation were modified by race. Proportional hazards models were used to evaluate whether race modified associations between tumor methylation and time to all-cause mortality. Greater fruit consumption was associated with greater odds of high NEUROG1 methylation among EA at methylation cut points of 15-35% (maximum OR 3.44, 95% CI 1.66, 7.13) but not among AA. Higher folate intake was associated with lower odds of high CACNA1G methylation among EAs but not AAs. Tumor methylation was not associated with all-cause mortality for either group. Race might modify associations between lifestyle factors and colorectal tumor methylation, but in this sample did not appear to modify associations between tumor methylation and all-cause mortality.