Background. Evidences which prove relation between breastfeeding women and risk of breast cancer have been limited. Objective. A meta-analysis was carried out on the basis of published literature from clinical trials and studies among different parts of the world. Methods. Studies were analyzed and extracted using PRISMA flowchart. RevMan 5.4.1 was used for analyzing the extracted data. Included studies were fully cited texts with complete information about studies, trails conducted for risk of breast cancer, and breastfeeding correlations. Results. Menarche age, family history, lactation duration, and menopausal status have a strong effect on the risks of breast cancer. Family history studies concluded that for 95% CI, the risk ratio was 2.66 (2.00, 3.52). Conclusion. Findings have suggested that family history and lactation duration affect the risks of breast cancer.

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Background: Some breast cancer patients are prone to recurrence and metastasis. Increasing evidence suggests that the breast tissue contains a diverse population of bacteria, which may be modulating the risk of breast cancer development or progression. However, the extent of microbial contribution to the tumor immune microenvironment in breast cancer remains unknown. Here, we explored the potential in uence of the tumor microbiota on the local immune microenvironment and breast cancer prognosis.Methods: Using 16S rRNA gene sequencing, we analyzed the tumor microbiome composition and identi ed bacteria that were differentially abundant between breast cancer patients with recurrence or metastasis (R/M) and those without recurrence or metastasis (NRM). We performed total RNA sequencing in tumor tissues from patients in both groups to determine differentially expressed genes (DEGs). The landscape of tumor-in ltrating immune cells (TIICs) subtypes in the tumor immune microenvironment was analyzed using CIBERSORT, based on the gene expression pro ling of tumor tissues. Differences in the tumor microbiomes were then correlated with DEGs and differences in TIICs, in order to determine how microbial abundance may contribute to cancer progression.Results: Microbial alpha-diversity was higher in NRM patients than in R/M patients. The composition and functions of the tumor microbiome communities differed between the two groups. We found higher alpha-diversity, higher abundance of Ruminococcus, Butyrivibrio, and Deinococcus, and lower abundance of Microbacterium could serve as a predictor of better prognosis in breast cancer patients. We also found that 16 genes, including CD36, showed differential expression in NRM compared to R/M, and differences in the composition of TIICs were observed between the two groups. In addition, we observed that the different tumor microbiome pro les were associated with DEGs and differences in TIICs between the two groups.Conclusions: The tumor microbiome may affect the prognosis of breast cancer patients by in uencing the tumor immune microenvironment. Thus, the tumor microbiome may be a useful prognostic indicator. BackgroundMicrobes colonize areas that are directly exposed to the air and surroundings, including the mouth, nostrils, skin, stomach, and the gastrointestinal and urogenital tracts [1]. Viral or bacterial infection is the third highest contributor to the development of cancer [2,3]. It is estimated that 15-20% of malignancies are caused by microbial pathogens, and even more malignancies are related to alterations in microbial communities that colonize human tissues [3][4][5][6]. The microbiome is associated with a variety of malignancies, including gastric, colon, liver, lung, and skin cancers and lymphoma. Perhaps the strongest linkages so far have been found between gastric cancer and Helicobacter pylori, and between colon cancer and Fusobacterium [7][8][9][10][11][12]. The microbiome may contribute to carcinogenesis by inducing chronic in ammation, altering cellular processes, ...