Breast cancer risk in young women suggests need for early monitoring

An MRI study of risk factors for breast cancer in young women, including teenagers, concluded that risk assessment and prevention should start much earlier in life than previously recommended. The Canadian study suggests using imaging techniques that avoid patient exposure to ionizing radiation.

Researchers have known for years that mammographic density is a significant risk factor for breast cancer, meaning breast cancer risk increases as mammographic density increases. Until now, however, little was known about mammography density in young women and how it relates to height, weight, and age.

Dr. Norman Boyd of the Campbell Family Institute for Breast Cancer Research in Toronto and colleagues recruited 400 women aged 15 to 39 and their mothers. To measure mammographic density, the researchers used MRI because it gives an indication similar to a mammogram without radiation exposure. Of 365 mothers, the researchers also randomly selected 100 to receive an MRI as well as a mammogram.

The group found the percentage of breast water measured by MRI strongly correlated to the percentage of mammographic density measured by mammogram. Breast water percentage in daughters (a median of 45%) was significantly higher than in mothers (28%). Breast water decreased with age and weight gain but increased with height.

The current study shows that each 5 cm difference in height in daughters was associated with a 3% increase in percentage of breast water, which suggests that growth might affect breast cancer risk.

Weight, height, and mother's mammographic density are known risk factors for breast cancer, according to the researchers.

Mammographic density may arise from a subset of the population with the greatest amount of fibroglandular tissue in early life when susceptibility to carcinogens is the greatest, according to Boyd. His findings suggest differences in breast tissue composition in early life may be a potential mechanism for this increased susceptibility.

The study is part of a broader effort to identify the environmental and genetic factors that influence changes in a woman's breast tissue composition over time and to develop methods of breast cancer prevention that may be safe and effective when initiated earlier in her life, Boyd said.