Association between Dietary Indices and Dietary Patterns and Mortality and Cancer Recurrence among Cancer Survivors: An Updated Systematic Review and Meta-Analysis of Cohort Studies

The number of cancer survivors is growing rapidly; however, specific lifestyle recommendations for these patients are still sparse, including dietary approaches. Thus, the aim of the present systematic review and meta-analysis was to examine the associations between adherence to diet-quality indices and dietary patterns on overall mortality, cancer-specific mortality, and cancer recurrence among cancer survivors. The literature search was conducted in PubMed and Web of Science between 18 May 2016 and 22 May 2022 with no language restrictions. Thirty-nine studies were included for quantitative analysis, providing data from 77,412 participants. Adherence to both diet-quality indices and a healthy/prudent dietary pattern was inversely associated with overall mortality (RR, 0.81; 95% CI, 0.77-0.86; RR, 0.80; 95% CI, 0.70-0.92, respectively) and with cancer-specific mortality (RR, 0.86; 95% CI, 0.79-0.94; RR, 0.79; 95% CI, 0.64-0.97, respectively). These associations could be observed following assessment of dietary patterns either pre- and/or postdiagnosis. For unhealthy/western dietary patterns, high adherence was associated with overall mortality (RR, 1.26; 95% CI, 1.08-1.47). Although the certainty of evidence was rated as low, we conclude that there are no reservations against high adherence to healthy dietary patterns or indices in cancer survivors.