Mediterranean Diet Adherence Tools in Post-Treatment Breast Cancer Survivors: A Scoping Review of Measurement Approaches and Associated Outcomes.

BACKGROUND

Nutrition is an important yet underexplored determinant of cancer survivorship outcomes. Emerging evidence suggests that greater adherence to the Mediterranean diet (MedD) is associated with improved health status, enhanced quality of life (QoL), and reduced mortality. However, evidence specifically targeting post-treatment breast cancer survivors remains limited, and substantial heterogeneity in MedD scoring tools and adherence thresholds restricts comparability across studies. This review aimed to (i) identify and characterise the tools used to assess MedD adherence in breast cancer survivors following completion of active treatment, including their components, scoring systems, and adherence thresholds; and (ii) map the range of health outcomes that have been examined in relation to MedD adherence in this population.

METHODS

A scoping review was conducted in accordance with PRISMA-ScR and Joanna Briggs Institute guidelines. PubMed, Embase, Scopus, Web of Science, and CINAHL were searched (2000-2026) for English-language intervention and observational studies reporting MedD adherence in adult female breast cancer survivors after treatment completion. Two reviewers independently extracted data, which were synthesised descriptively, including study characteristics, MedD scoring tools, adherence outcomes, and clinical, metabolic, and QoL findings. The methodological structure protocol of this scoping review was retrospectively registered in the Open Science Framework.

RESULTS

Twenty studies (16 intervention, 4 observational; 16 non-overlapping cohorts; pooled n N = 4174, excluding non-cancer comparators) met inclusion criteria. Ten MedD scoring tools were identified, most frequently MEDAS-14 (original or modified, 7/20 studies), varying in components (range 9-18), scoring approach, and adherence thresholds. Most intervention studies reported improved MedD adherence following intervention, generally as a within-group change; between-group differences in adherence were reported less often and inconsistently significant. Anthropometric outcomes (body weight, body mass index (BMI), waist circumference) were most frequently improved, but significant differences between groups were found in only a small number of controlled studies. Mortality was assessed in only one observational cohort study, which found no association with breast-cancer-specific outcomes.

CONCLUSIONS

This scoping review identified considerable heterogeneity in how MedD adherence is measured in breast cancer survivors, with ten different scoring tools identified across 20 studies. Although improvements in MedD adherence appear achievable, the evidence is limited by small sample sizes, heterogeneous assessment tools, and short intervention durations. Larger, standardised longitudinal studies are needed, particularly to determine whether MedD adherence influences cancer recurrence and survival, for which current evidence remains minimal.