OCI investigators have conducted a unique mother-daughter study that provides further understanding of breast density, an inheritable characteristic known to be a strong risk factor for breast cancer, and suggests that risk assessment and prevention of breast cancer might start early in life.

Led by Dr. Norman Boyd, the team recruited 400 pairs of mothers and daughters and used Magnetic Resonance Imaging (MRI) to examine breast tissue in daughters, aged 15-30 years, as well as a random sample of 100 of the mothers. Mothers underwent mammography and a random sample of 100 also consented to have a breast MRI. Results showed that percent breast water variation was higher in 15-19 year olds than in 20-30 year olds, and that this variation decreases with age.

Height and weight, the mothers' breast tissue characteristics, and higher blood growth hormone concentrations were also linked to higher percent breast water. The team found that every additional 5 cm in the daughters' heights was associated with a 3% increase in percent breast water, which suggests a mechanism by which growth might affect the risk of cancer.

"Our findings suggest that differences in breast tissue composition in early life may be a potential mechanism for this increased susceptibility to the effects of carcinogens at early ages," comments Dr. Boyd. "By identifying the environmental and genetic factors that influence breast tissue composition early in life, we may be able to develop safe and effective methods of prevention."

Boyd N, Martin L, Chavez S, Gunasekara A, Salleh A, Melnichouk O, Yaffe M, Friedenreich C, Minkin S, Bronskill M. [Pubmed abstract]. Research supported by the Canadian Breast Cancer Research Alliance, the Lau Chair in Breast Cancer Research.