Diet quality and all-cause and cancer-specific mortality in cancer survivors and non-cancer individuals: the Multiethnic Cohort Study

We examined post-diagnostic diet quality in relation to all-cause and cancer-specific mortality among adults diagnosed with invasive cancer between cohort entry (45–75 years) and their 10-year follow-up, in comparison with those without invasive cancer during that period, in the Multiethnic Cohort. Data were from 70,045 African Americans, Native Hawaiians, Japanese Americans, Latinos, and Whites (6370 with cancer, 63,675 without cancer). Diet quality was measured by the Healthy Eating Index (HEI)-2015, the Alternative HEI-2010 (AHEI-2010), the alternate Mediterranean Diet (aMED), and the Dietary Approaches to Stop Hypertension (DASH) scores, using a food frequency questionnaire. Multivariable Cox models estimated the association of the dietary indexes at 10-year follow-up and changes since baseline with subsequent mortality. Post-diagnostic scores from all four indexes were associated with lower mortality: for the highest vs. lowest quartiles, hazard ratio (HR) for all-cause mortality was 0.74 (95% CI 0.67–0.82) for HEI-2015, 0.82 (0.74–0.92) for AHEI-2010, 0.74 (0.66–0.84) for aMED, and 0.82 (0.74–0.91) for DASH. The corresponding HRs for cancer mortality were 0.84 (0.71–1.00), 0.85 (0.71–1.00), 0.71 (0.59–0.85), and 0.84 (0.71–1.00). Compared to stable scores over 10 years (< 0.5 SD change), HR for all-cause mortality was 0.87 (0.79–0.97) for ≥ 1 SD increase in HEI-2015 and was 1.22 to 1.29 for ≥ 1 SD decrease in scores across the four indexes. These HRs were similar to those for participants without cancer. Post-diagnostic high-quality diet was related to lower all-cause and cancer mortality among adult cancer survivors, with risk reduction comparable to that among participants without cancer.