Causes of breast cancer
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Key Risk Factors and Causes of Breast Cancer
Hormonal and Reproductive Factors in Breast Cancer
Hormonal factors play a major role in the development of breast cancer. Prolonged exposure to endogenous estrogens and progesterone—such as from early onset of menstruation (menarche), late menopause, not having children (nulliparity), or having children later in life—can increase risk by promoting excessive proliferation of breast cells, which may lead to cancerous changes over time Macmahon2006Thomas1984Momenimovahed2019. Use of exogenous hormones, such as hormone replacement therapy, is also recognized as a risk factor Macmahon2006Thomas1984.
Genetic and Molecular Causes
Breast cancer is a molecularly heterogeneous disease, with genetic mutations such as those in BRCA1 and BRCA2 genes significantly increasing risk. Genomic instability, caused by defects in DNA repair and other cellular processes, contributes to the development and progression of breast cancer Sun2017Testa2020Smolarz2022. However, most breast cancer cases occur in women without these high-risk genetic mutations Løyland2024Testa2020.
Environmental and Lifestyle Factors
Environmental exposures, including ionizing radiation and certain chemical pollutants (like persistent organic pollutants and endocrine disruptors), have been linked to increased breast cancer risk. These chemicals may influence cancer development by affecting cell signaling pathways and promoting processes like metastasis and drug resistance Macmahon2006Hiatt2018Koual2020. Lifestyle factors such as alcohol consumption are also established risk factors Macmahon2006Momenimovahed2019.
Socioeconomic and Demographic Influences
Breast cancer incidence is higher in developed countries and among women with higher socioeconomic status and education levels. This pattern suggests that lifestyle and reproductive choices associated with these groups may contribute to risk, although the exact causes remain unclear Løyland2024Momenimovahed2019. Additionally, incidence rates vary by race and ethnicity, with mortality rates higher in less developed regions .
Breast Density and Other Biological Factors
High breast density is one of the strongest risk factors for breast cancer, while higher levels of sex-hormone-binding globulin appear to be protective . Other biological factors, such as breast-related conditions and certain hereditary traits, also contribute to risk .
Uncertainties and Ongoing Research
Despite extensive research, there is still no clear consensus on many of the causes and risk factors for breast cancer. Many studies report conflicting results, and recommendations about lifestyle changes should be made with caution . The role of environmental chemicals and the mechanisms by which they influence breast cancer progression are still being explored Hiatt2018Koual2020.
Conclusion
Breast cancer is a complex disease with multiple contributing factors, including hormonal, genetic, environmental, lifestyle, and socioeconomic influences. While some causes—such as exposure to radiation, exogenous hormones, and alcohol—are well established, the majority of cases occur without these exposures, and much remains unknown about the underlying causes. Continued research is needed to clarify these factors and improve prevention strategies.
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