Associations of pre- and postdiagnosis diet quality with risk of mortality among men and women with colorectal cancer

Purpose Dietary patterns, indicators of overall diet quality, are associated with colorectal cancer (CRC) incidence but less consistently with mortality among CRC survivors. We prospectively evaluated associations of diet quality pre- and postdiagnosis with risk of mortality among men and women with CRC. Patients and Methods In the Cancer Prevention Study-II Nutrition Cohort, 2,801 participants were cancer free at baseline in 1992/1993 and subsequently diagnosed with invasive, nonmetastatic CRC during follow-up through June 2013. Pre- and postdiagnosis diet data were available for 2,671 and 1,321 participants, respectively, among whom 1,414 and 722 died. Concordance with the Dietary Approaches to Stop Hypertension (DASH), American Cancer Society nutrition guidelines (ACS-score), prudent, and Western dietary patterns was used to evaluate diet quality. Results Extreme scoring group comparisons showed that prediagnosis ACS-score was inversely associated with all-cause (hazard ratio high v low [HR_{High vLow}], 0.78; 95% CI, 0.65 to 0.95) and CRC-specific (HR_{High vLow}, 0.74; 95% CI, 0.54 to 1.03) mortality, whereas the Western diet score was associated with higher all-cause mortality (HR_{High vLow}, 1.30; 95% CI, 1.03 to 1.64). For postdiagnosis diet, the ACS-score was associated with lower risk of all-cause (HR_{High vLow}, 0.62; 95% CI, 0.47 to 0.83) and CRC-specific (HR_{High vLow}, 0.35; 95% CI, 0.17 to 0.73) mortality, the DASH score was inversely associated with all-cause (HR_HighvLow, 0.79; 95% CI, 0.62 to 0.99) and CRC-specific (HR_HighvLow, 0.56; 95% CI, 0.35 to 0.89) mortality, and the prudent score was inversely associated with all-cause mortality (HR_{High vLow}, 0.72; 95% CI, 0.56 to 0.93). Among participants with a low diet quality before diagnosis, improved DASH (HR, 0.54; 95% CI, 0.31 to 0.92) and prudent (HR, 0.53; 95% CI, 0.29 to 0.95) scores from pre- to postdiagnosis were inversely associated with CRC-specific mortality. Conclusion Dietary patterns reflective of high intakes of plant foods and low intakes of animal products before and after CRC diagnosis are associated with longer survival.