Abstract
Breast cancer is the most frequently diagnosed cancer in women worldwide. The disease and its treatments exert profound effects on an individual’s physical and mental health. There are many factors that impact an individual’s risk of developing breast cancer, their response to treatments, and their risk of recurrence. The community of microorganisms inhabiting the gastrointestinal tract, the gut microbiota, affects human health through metabolic, neural, and endocrine signaling, and immune activity. It is through these mechanisms that the gut microbiota appears to influence breast cancer risk, response to treatment, and recurrence. A disrupted gut microbiota or state of ‘dysbiosis’ can contribute to a biological environment associated with higher risk for cancer development as well as contribute to negative treatment side-effects. Many cancer treatments have been shown to shift the gut microbiota toward dysbiosis; however, the microbiota can also be positively manipulated through diet, prebiotic and probiotic supplementation, and exercise. The objective of this review is to provide an overview of the current understanding of the relationship between the gut microbiota and breast cancer and to highlight potential strategies for modulation of the gut microbiota that could lead to improved clinical outcomes and overall health in this population.
Highlights
Within the past 15 years, research into the gut microbiota has increased at an exponential rate [1]
The mechanisms through which the microbiota might exert its influence on carcinogenesis and cancer treatments require further investigation; some relationships are postulated to exist via microbiota-derived metabolites, modulation of host metabolism, alteration of cytokine expression, and immune regulation [6,7,8,9]
Additional clinical research is needed on the associations between gut microbiota and chemotherapy, but the composition of gut microbiota is being considered as a potential predictive biomarker for individual treatment response and target for improving outcomes [14,48,71]
Summary
Within the past 15 years, research into the gut microbiota has increased at an exponential rate [1]. The incidence of breast cancer and the number of survivors continues to grow, with many countries including the United States, Canada, England, Norway, Germany, Australia, and Japan reporting 85–90% five-year survival rates for women diagnosed between 2010 and 2014 [10,11] This large and growing population will benefit from novel interventions to support health during treatment, in survivorship, and to prevent recurrence of the disease [12]. Women who have had breast cancer have a greater risk of developing an additional health condition such as obesity, cardiovascular disease, or mental illness [12,20] These factors must be addressed in order to improve patient outcomes and quality of life [17,21]. The aim of this review is to describe the understood relationship between the gut microbiota and breast cancer, in the context of obesity, and identify potential interventional strategies and areas for further research that could improve health outcomes for this population
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