Effect of Probiotics in Breast Cancer: A Systematic Review and Meta-Analysis

SIMPLE SUMMARY: Probiotics possess potential to protect against breast cancer due to their immunomodulatory activity and their ability to impact the intestinal microbiota. Experimental studies have identified key probiotic microorganisms, but their clinical role in prevention of breast cancer and the efficacy of such supplements to control chemotherapy-induced side effects is less documented. A significant number of such intervention studies have recently been published, so we, therefore, conducted a systematic review and meta-analysis of all randomized clinical trials of probiotic use in breast cancer patients and survivors, including combination prebiotic use, to provide clarity regarding actions and role/benefit for preventive and palliative care. ABSTRACT: Probiotics may have the potential to protect against breast cancer, partly through systemic immunomodulatory action and active impact upon intestinal microbiota. Given a few clinical studies on their curative role, we conducted a systematic review of the potential effects of probiotics in breast cancer patients and survivors of breast cancer, aiming to support further clinical studies. A literature search was performed using PubMed, Embase, and the CENTRAL databases from inception through to March 2022. A total of eight randomized clinical trials were identified from thirteen articles published between 2004 and 2022. We evaluated quality-of-life measures, observed bacterial species and diversity indices, probiotic-related metabolites, inflammatory biomarkers, and other responses in breast cancer patients and survivors. Results were synthesized qualitatively and quantitatively using random-effects meta-analysis. Different probiotics supplements utilized included Lactobacillus species alone (Lacto), with or without estriol; probiotic combinations of Lactobacillus with Bifidobacterium (ProLB), with or without prebiotic fructooligosaccharides (FOS); ProLB plus Streptococcus and FOS (ProLBS + FOS); and ProLB plus Enterococcus (ProLBE). We found that use of ProLBS with FOS in breast cancer patients and use of ProLBE in survivors of breast cancer show potential benefits in countering obesity and dyslipidemia. ProLBS with FOS use decreases pro-inflammatory TNF-α in breast cancer survivors and improves quality of life in those with breast-cancer-associated lymphedema. Supplementing probiotics capsules (10(9) CFU) with a prebiotic and using an intake duration of 10 weeks could provide a better approach than probiotics alone.