Adherence to the Western, Prudent and Mediterranean dietary patterns and breast cancer risk: MCC-Spain study

OBJECTIVE: To externally validate the previously identified effect on breast cancer risk of the Western, Prudent and Mediterranean dietary patterns. STUDY DESIGN: MCC-Spain is a multicase-control study that collected epidemiological information on 1181 incident cases of female breast cancer and 1682 healthy controls from 10 Spanish provinces. Three dietary patterns derived in another Spanish case-control study were analysed in the MCC-Spain study. These patterns were termed Western (high intakes of fatty and sugary products and red and processed meat), Prudent (high intakes of low-fat dairy products, vegetables, fruits, whole grains and juices) and Mediterranean (high intake of fish, vegetables, legumes, boiled potatoes, fruits, olives, and vegetable oil, and a low intake of juices). Their association with breast cancer was assessed using logistic regression models with random province-specific intercepts considering an interaction with menopausal status. Risk according to tumour subtypes - based on oestrogen (ER), progesterone (PR) and human epidermal growth factor 2 (HER2) receptors (ER+/PR+ & HER2-; HER2+; ER-/PR- & HER2-) - was evaluated with multinomial regression models. MAIN OUTCOME MEASURES: Breast cancer and histological subtype. RESULTS: Our results confirm most of the associations found in the previous case-control study. A high adherence to the Western dietary pattern seems to increase breast cancer risk in both premenopausal women (OR4thvs.1stquartile (95% CI):1.68 (1.02;2.79); OR1SD-increase (95% CI):1.19 (1.02;1.40)) and postmenopausal women (OR4thvs.1stquartile(95% CI):1.48(1.07;2.05); OR1SD-increase(95% CI): 1.14 (1.01;1.29)). While high adherence to the Prudent pattern did not show any effect on breast cancer, the Mediterranean dietary pattern seemed to be protective, but only among postmenopausal women (OR4thvs.1stquartile (95% CI): 0.72 (95% CI 0.53;0.98); p-int=0.075). There were no significant differences by tumour subtype. CONCLUSION: Dietary recommendations based on a departure from the Western dietary pattern in favour of the Mediterranean diet could reduce breast cancer risk in the general population.S