Women with dense breasts have a higher risk of breast cancer than women with less dense breasts. Compared to non-dense breasts, dense breasts have less fatty tissue and more fibrous and glandular tissue. Breast fibrous and glandular tissue is mainly made up of water. The study reviewed here suggests that figuring out the water content of a young woman's breast tissue may help predict her risk of breast cancer in later life.
The researchers used MRI to determine the water content of breast tissue in 400 young women aged 15 to 30. The researchers also determined the breast density of most of the young women's mothers using mammograms or by determining the water content of their breast tissue using MRI. The researchers then compared the results of the daughters' breast tissue water content and the mothers' breast density. The researchers used MRI to determine breast tissue water content in the young women because a mammogram would have exposed the young women to a level of radiation that was considered inappropriate for their age for strictly research purposes.
The results:
While determining the breast density or breast tissue water content of young women isn't done routinely, this study suggests that breast tissue water content might be a good way to estimate the breast density of young women. Since denser breasts are linked to higher breast cancer risk, measuring the breast tissue water content may help assess a young woman's future breast cancer risk. More research is needed to figure out if breast tissue water content can be a practical tool for young women who want to know as much as they can about their individual risk level.
RIDGEWOOD, N.J., April 30 (MedPage Today) -- Measurement of breast tissue composition in young women may help predict their risk for breast cancer in later life, new research suggests.
In the first study of its kind, MRI revealed that in young women, the percent of water in the breast tissue -- which reflects the proportion of fibroglandular tissue -- was positively associated with their mothers' percent mammographic density (P<0.0001), according to Norman Boyd, M.D., of the Campbell Family Institute for Breast Cancer Research in Toronto, and colleagues.
Mammographic density, a "highly heritable" measure of breast tissue composition in adult women, is a significant risk factor for breast cancer, the investigators noted in an online report in Lancet Oncology.
"We have previously shown that the water content of the breast, measured by MRI, is strongly correlated with percent mammographic density," they said.
In addition, the percent of water in the daughters' breast tissue was positively associated with their height (P<0.0001).
Greater adult height is associated with a higher percent mammographic density, and greater height at age 14 years was strongly associated with later breast cancer in a Danish study.
Breast tissue is most susceptible to the effects of carcinogens at early ages, as was seen in Japan after the atomic bomb explosions in World War II. Women younger than 20 years at the time of exposure to radioactive fallout had the highest incidence of breast cancer in later life.
However, little is known about actual breast tissue composition during the early years of life, so Dr. Boyd and his colleagues recruited 400 young white women, aged 15 to 30 years, and their mothers.
Rather than performing mammograms on the young women, which would have exposed them to ionizing radiation, the Canadian researchers used MRI to determine the proportion of breast water and fat.
A total of 356 mothers provided access to their mammograms, and a random sample of 100 of the mothers also had MRI examinations.
Percent water in the daughters' breast tissue, at a median of 45%, was significantly higher than the percent in the mothers' breasts, at a median of 28% (P<0.0001), and was independently inversely associated with the daughters' age (P=0.04) and weight (P<0.0001).
"After adjustment for weight and other factors, our data showed that each 5 cm difference in height in daughters was associated on average with a 3% increase in percent breast water . . . which suggests a mechanism by which growth might affect the risk of breast cancer," the investigators said.
Analysis of serum concentrations of growth factors and hormones in a subgroup of 280 young women who had not used oral contraceptives within the previous six months also showed positive associations.
After adjustment for covariates including age at menarche, physical activity, and mothers' age, weight, and height, growth hormone was significantly and positively associated with the young women's percent breast water (P=0.04).
This association of serum concentrations of growth hormone (the primary mediator of postnatal growth) and percent breast water suggests a central role for growth hormone in the development of breast cancer, the investigators said.
Growth hormone, they explained, influences growth through interaction with the cell-surface growth-hormone receptor, and by releasing insulin-like growth factors from the liver, breast and other sites. The growth hormone gene also is expressed in epithelial and stromal cells of the breast.
Additionally, sex hormone binding globulin was significantly associated with percent breast water (P=0.001). This hormone, the researchers suggested, might contribute to mitogenesis in breast tissue through the stimulation of intracellular messengers of cell proliferation.
"Our results suggest a potential mechanism for susceptibility to breast carcinogens at early ages, identify factors associated with breast tissue composition in young women, and suggest a model and a hormonal mechanism for the origins of mammographic density in early life," they said.
In a press release, Dr. Boyd said, "It is known that the breast is most susceptible to the effects of carcinogens at early stages. Our findings suggest that differences in breast tissue composition in early life may be a potential mechanism for this susceptibility.
"By identifying the environmental and genetic factors that influence breast tissue composition in early life, we may be able to develop safe and effective methods of prevention."
This research was supported by the Canadian Breast Cancer Research Alliance.
Primary source: Lancet Oncology Source reference: Boyd N, et al "Breast tissue composition and other risk factors for breast cancer in young women: a cross-sectional study" Lancet Oncol 2009; DOI: 10.1016/S1470-2045(09)70078-6.
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