Mediterranean diet is protective for preventing breast cancer recurrence especially in postmenopausal women, but the Western diet seems to increase breast cancer risk in both premenopausal women and postmenopausal women.
Castelló A, Boldo E, Pérez-Gómez B, Lope V, et al. Adherence to the Western, Prudent and Mediterranean dietary patterns and breast cancer risk: MCC-Spain study. Maturitas. 2017 Sep;103:8-15. doi: 10.1016/j.maturitas.2017.06.020. https://www.ncbi.nlm.nih.gov/pubmed/28778338