How reproductive history can affect breast cancer risk

FALLBROOK – Various factors can contribute to the development of breast cancer. Many women may not be aware that their own reproductive history could be affecting their risk.

Data published by Frontiers Research: Oncology, which has culled information from the Metastasis Research Library, School of Cancer Medicine and Robinson Research Institute, among other medical groups in Australia, indicated that there is a correlation between the amount of reproductive estrogen present in a woman's body and her chances of developing breast cancer.

There is evidence that women who either enter menarche at a young age or cease menstruation at a later age, have an increased risk for breast cancer. Fluctuating estrogen and progesterone during menstrual cycles can affect mammary epithelial cells, immune cells and the extracellular matrix, according to a 2011 study titled "The immune hallmarks of cancer," that was published in the journal Immunotherapy.

The Centers for Disease Control and Prevention said women who had early menstrual periods, before age 12, or those who started menopause after age 55 are exposed to estrogen longer, increasing their risk of getting breast cancer. Susan G. Komen Foundation advised that, according to a pooled analysis of data from more than 400,000 women, for every year older a woman was at menopause, her breast cancer risk increased about 3%.

Before menopause, estrogen in the bloodstream is largely caused by the production of estrogen in the ovaries. After menopause, when the ovaries stop producing estrogen naturally, estrogen can be produced by stores in body fat. Women who have a higher concentration of body fat or are largely sedentary may have higher levels of estrogen, which affects their cancer risk.

Conversely, although reproductive hormones are elevated during pregnancy, having children helps reduce breast cancer risk over time. Data published in the Lancet in 2002 reveals after a transient increase in risk for breast cancer, peaking at about five years after giving birth, having at least one child is associated with a decrease in the long-term risk of developing breast cancer compared with the risk among women who never had children. This protective effect increases with number of children had; each birth reduces the relative risk of breast cancer by about 7%.

Reproductive history is another consideration in breast cancer development. Women can speak to their gynecologists if they suspect a high risk due to estrogen exposure.