GENETIC AND ENVIRONMENTAL DETERMINANTS OF MAMMOGRAPHIC DENSITY: A TWINS AND SISTERS STUDY [ 2004 - 2006 ]

Research Grant

Researchers: Prof John Hopper (Principal investigator) ,  Dr Gillian Dite ,  Dr Susan Treloar ,  Prof Melissa Southey ,  Prof Norman Boyd

Brief description Breast cancer is a major cause of early death and disability in Australian women. Breast density, a characteristic of women's breast that can be mesured by mammograms such as those conducted by BreastScreen, has been shown by a number of large studies to be a major risk factor for breast cancer. It is a characteristic that cannot be measured by breast examination, but is very well measured by a breast scan. Although breast density decreases with age at and after menopause, there is a large difference in breast density across women of the same age. Identifying the reasons why women of the same age differ so much in breast density will lead to a better understanding of the causes of breast cancer and have implications for prevention. We have conducted a large twin study, in collaboration with Dr Norman Boyd in Toronto, Canada, that has shown that most of this large variation in breast density could be due to as yet undiscovered genetic factors. The genes involved are not BRCA1 and BRCA2, the currently known breast cancer susceptibility genes. We have also found that lifestyle factors, such as number of children, also influences breast density. In this larger study of twins and sister pairs, we shall test whether specific hormone genes, such as those involved with estrogen and progesterone, explain part of the genetic effects. We will also study more closely the effects of environmental and lifestyle factors on breast density, especially how their effects interact with those of any genetic factors we identify, by comparing twins and sister of the same or similar age. By studying women who have had endometriosis, we will be able to find out if their small increased risk of breast cancer is reflected in their breast density. By collecting a blood sample from all participants we will build a large resource that will be used for future genome scan studies, trying to discover new genes that influence breast density, and by implication, risk of breast cancer.

Funding Amount $AUD 703,100.00

Funding Scheme NHMRC Project Grants

Notes Standard Project Grant