The normal aging of breast tissue lowers the risk of cancer, according to a new study.

As women get older, and especially after the menopause, the milk-producing glands - known as lobules - shut down. This process is called involution. Since breast cancer originates in the lobules, their reduced size and number decreases the risk of cancer. Women who experience complete involution have half the risk of developing breast cancer compared to those who do not.

Researchers at the Mayo Clinic have taken a detailed look into involution and breast cancer in a new study. They looked at 8,736 women who had benign breast biopsies at the Clinic during a 25 year period. The extent of involution was determined in tissue samples from these women. They were already at 40 per cent increased risk of breast cancer because of having benign disease and were compared to a group of healthy women. Those women in the Mayo group with complete involution were at no more risk of breast cancer than the healthy women.

The researchers learned that hormone replacement therapy made women less likely to experience complete involution than those who had never been on it. Those having more than three children were likely to retain more breast lobules. The findings suggest that documenting involution status in a woman's background breast tissue can be a useful aid in predicting her risk of breast cancer.

Source
Journal of the National Cancer Institute 15th November 2006