What is the association between estrogen and breast cancer?

Abstract

Aim: There is a historical acceptance about the causal relationship between Estrogens and Breast cancer which has either affected the incidence rate or mortality rate of breast cancer, or could have influenced the uptake or continuation of Estrogen in Hormone Replacement Therapy (HRT). Estrogens are useful either as Estrogen-only HRT (ERT) or as combined Estrogen and Progestogen HRT. There is now a need to clearly differentiate between ERT and HRT in their consequences with regard to breast cancer. This review documents the basis of the historical causal connection and the current situation Methodology: The literature was searched with the following key words: Estrogen, Breast cancer, Estrogen receptors and Menopause;. Incidence and mortality rates of breast cancer associated with Estrogen. Randomized controlled Trials, Observational studies. Cell proliferation, cell differentiation and cell development. Results: The relationship between Estrogen & Breast Cancer with regard to incidence and mortality requires a rigorous scrutiny because: There are prenatal influences which have an impact on exposure to Xenoestrogens across the life course, starting with conception – if not before, giving possible effects on germ cells and gametes. The evidence from observational studies should be interpreted with caution because of procedural inadequacies. The evidence that should be used for care of women is that from Randomised controlled trials because they are geared to infer on cause and effect relationships. The relationship between Estrogen alone for peri-menopause and menopause shows that it does not increase the risk of breast cancer or the mortality from breast cancer. Conclusion: Estrogen alone does not increase the risk and the mortality of breast cancer. The combination of ERT with a progestogen can increase the risk of breast cancer.