Breastfeeding as a Protective Factor against Breast Cancer: A Systematic Review

Breast cancer accounts for 24.5% of all cancer cases and 14% of all cancer deaths in women globally. Breastfeeding is thought to lower the risk of breast cancer mainly through two mechanisms; differentiation of breast tissue and a decrease in the total number of ovulatory cycles throughout a woman's lifetime. The objective of this systematic review is to investigate the published literature that studied breastfeeding and its duration as a possible protective factor for the development of breast cancer. PubMed, Web of Science, Science Direct, EBSCO, and Cochrane library were searched. Study articles were screened by title and abstract using Rayyan QCRI then a full-text assessment was implemented. Fifteen studies published between 2000 and 2022 with a total of 27315 breast cancer patients were included. Most included studies reported that breastfeeding and its longer duration play a protective role against breast cancer. Only three studies reported no association between breastfeeding and breast cancer development. So, our systematic review found that breastfeeding, especially breastfeeding of longer duration, was considered a protective factor against breast cancer. Therefore, it was advised that data on breastfeeding duration should be gathered by researchers in order to possibly lower the incidence of breast cancer. If breastfeeding offers protection against breast cancer, a more thorough analysis of potential confounders may shed light on how this protection is achieved. This systematic review reported that breastfeeding, especially breastfeeding of longer duration, was considered a protective factor against breast cancer.