Aims Breast cancer survivors often seek information about how dietary intake effects prognosis. Previous studies have reviewed evidence around single nutrients, individual foods or food groups. We aimed to review the evidence around overall dietary intake and prognosis in breast cancer survivors.
Methods A systematic search of CINAHL, EMBASE, PubMed, and Scopus databases was conducted for studies published until June 2016. Eligible studies assessed overall dietary intake (i.e., diet quality; diet score; dietary pattern) and reported on associations with mortality and/or recurrence in breast cancer survivors.
Results We identified nine eligible studies (sample sizes: 670 to 7,495), with most studies following women >5 years post-diagnosis. Studies were heterogeneous with regard to diet assessment timing (before or after diagnosis); sample age and menopausal status; and measure of dietary intake (statistically derived or a priori defined diet quality indices). Most studies controlled for potentially important confounding variables including disease stage, BMI, energy intake, and physical activity level. Better overall dietary intake (i.e. better diet quality; healthy/prudent dietary pattern; less inflammatory diet) was associated with decreased risk of overall mortality, and non-breast cancer mortality, in the majority of studies. Inconsistent associations were observed for breast cancer-specific mortality, with three of nine studies reporting significant protective associations, one reporting an adverse association, and five reporting no associations. Inconsistent associations were also observed among the three studies which examined recurrence.
Conclusions Following breast cancer diagnosis, better overall dietary intake may improve overall and non-breast cancer survival, independent of disease stage at diagnosis, BMI, energy intake and physical activity level. Evidence for breast cancer-specific survival suggests a possible protective association, though results were varied. Thus, breast cancer survivors may improve overall survival by adopting more healthful dietary patterns consistent with dietary guidelines and/or prudent diet. Future studies should consider using consistent approaches to measuring dietary intake.