The association between the adapted dietary inflammatory index and colorectal cancer recurrence and all-cause mortality.

Summary Background & aim The inflammatory potential of the diet has been linked to colorectal cancer (CRC) development and mortality. However, it is unknown whether it is also associated with CRC recurrence. Therefore, the aim of this study was to investigate the associations between the inflammatory potential of the diet and plasma inflammation markers as well as recurrence and all-cause mortality in CRC patients. Methods Data of the Colorectal cancer, Observational, LONgitudinal (COLON) study, a prospective cohort study, was used. Dietary intake, assessed using a semi-quantitative food frequency questionnaire, was available for 1,478 patients at diagnosis and for 1,334 patients six months after diagnosis. Dietary intake data were used to calculate the adapted dietary inflammatory index (ADII). Data about cancer recurrence and all-cause mortality, were assessed through linkage with the Netherlands Cancer Registry and the Municipal Personal Records Database, respectively. The association between the ADII (continuous) and inflammation markers (Interleukin (IL)6, IL8, IL10, Tumor Necrosis Factor(TNF)α, high sensitivity C-reactive protein (hsCRP) and a summary inflammatory z-score), measured with a multiplex assay using electrochemiluminiscence detection, was assessed using quantile regression analyses. Restricted cubic splines (RCS) analyses and multivariable Cox proportional hazard models were used to explore the relationship between the ADII and CRC outcomes. Results During a median follow-up time of 3.2 years (Interquartile range (IQR) 2.0-4.1) for recurrence and 4.8 years (IQR 3.5-5.9) for all-cause mortality, 228 recurrences and 279 deaths occurred. A more pro-inflammatory diet at diagnosis as well as six months after diagnosis was associated with higher levels of TNFα, hsCRP and the summary inflammatory z-score. Results of RCS showed no relationship between the ADII and CRC outcomes at both time points. Also results of the Cox proportional hazard models showed no associations between the ADII at both time points and recurrence (HR (95%CI) 0.98 (0.94-1.04) & 0.96 (0.91-1.02) or all-cause mortality (HR (95%CI) 1.03 (0.98-1.07) & 1.00 (0.95-1.05)). Conclusion Our study did not show an association between the ADII and recurrence and all-cause mortality in CRC patients. Further research should also take into account molecular tumor subtypes, as the effect of the inflammatory potential of the diet on cancer recurrence and mortality is more likely to be present in tumors with an inflammatory signature. Clinical Trial Registry numbers and website. The COLON study NCT03191110; clinical trials.gov .