The Breast Cancer Personalized Nutrition Study

Weight gain is a common incident in breast cancer survivors. As many as 50-96% of women experience weight gain during treatment. Endocrine treatment was identified as a risk factor for weight gain in several studies. Hence, weight management for breast cancer survivors is important for increasing adherence to therapy and lowering recurrence risk. The essential role of the gut microbiota in modulating immune and metabolic functions in health and disease is increasingly recognized. Particularly in breast cancer (BC), diet plays an important role in creating a microbiome environment involved in estrogens metabolism. The microbiome directly affects the body's response to food. The Personalized Nutrition Project, conducted in the Weizmann Institute of Science, showed that individuals vary greatly in their glycemic response to the same food, influenced by the involvement of functional microbial pathways. This study yielded an algorithm capable of accurately predicting personalized postprandial glycemic response (PPGR) to arbitrary meals. These results suggest that individually tailored dietary interventions help maintain normal blood glucose levels and influence microbiome diversity, which, in turn, can control weight changes. In this phase 2 randomized trial, 200 Hormone receptor (HR) positive breast cancer patients, eligible for adjuvant endocrine therapy will be recruited to the study. Upon recruitment, subjects will provide a stool sample for microbiome analysis and will undergo continuous glucose monitoring for 2 weeks. Thereafter, patients will be randomly assigned in a 1:1 ratio to receive a personalized diet recommendation or a standard low-fat diet for 6 months. The algorithm is based on patients' microbiome analyses and other blood tests. Patient clinical records will be followed 2-3 times yearly for 5 years for DFS and BC recurrence.