The effect of Diet on Breast Cancer recurrence: the DIANA-5 randomized trial

Purpose: The DIANA-5 randomized controlled trial assessed the effectiveness of a diet based on Mediterranean and macrobiotic traditions (macro-Mediterranean® diet) in reducing BC recurrence. Patients and methods: The DIANA-5 study involved 1542 breast cancer patients at high risk of recurrence because of ER-negative cancer, or metabolic syndrome, or high plasma levels of insulin or testosterone. Women were randomly assigned to an active dietary intervention (IG) or a control group (CG). Both groups received the 2007 AICR/WCRF recommendations for cancer prevention. The intervention consisted of meetings with kitchen classes, community meals, and dietary recommendations. Recommended foods included whole grain cereals, legumes, soy products, vegetables, fruit, nuts, olive oil and fish. Foods to be avoided were refined products, potatoes, sugar and desserts, red and processed meat, dairy products and alcoholic drinks. A compliance Dietary Index was defined by the difference between recommended and discouraged foods. Results: Over the 5-years of follow-up 95 patients of the IG and 98 of the CG developed breast cancer recurrence (HR= 0.99, 95% CI 0.69-1.40). The analysis by compliance to the dietary recommendations (IG and CG together) showed that the women in the upper tertile of Dietary Index change had a HR of recurrence of 0.59 (95% CI:0.36-0.92) compared to women in the lower tertile. Conclusions: The DIANA-5 dietary intervention trial failed to show a reduction in breast cancer recurrence, although self-reported diet at year one in IG and CG combined showed a protective association with the higher dietary index change.