Mammogram Density, Cancer, Inheritance &amp; Acquired Risk:Twins
Creators: name: University Of California Office Of The President
Publisher: name: University of California Office of the President
publisherIdentifier: https://ror.org/00dmfq477
publisherIdentifierScheme: ROR
Year: 2024

description: Currently available risk factors for breast cancer are not very useful on a population basis in identifying women at high risk for purposes of targeted intervention. Using the mammograms of normal women, the proportion of the mammographic area that is relatively dense appears to be a stronger and more comprehensive predictor of breast cancer than any other practical index. If true, not only could this factor single out women for special intervention, it might also serve as a surrogate or "stand-in" representing breast cancer risk for testing interventions more quickly and at much lower than usual cost. That is, rather than having to follow a group of women for many years to see if a certain intervention has resulted in fewer cancers, it might be possible, over a shorter time, to see if there were changes in breast density (as shown on a mammogram) as a result of the intervention. However, before mammograms can be considered for these purposes, the predictive value obtained using them must be assessed under stringent conditions and the determinants of mammographic density that are heritable and those that are acquired during a woman’s life better understood.
 
 
 
 
 
 
 
 We will identify twin pairs from a pool of 2500 pairs who are known to have had screening mammograms since 1984 and within 5 years of each other. Of these twin pairs, 550 are pairs in whom one twin has had breast cancer and in whom the healthy twin had a mammogram within 5 years of her twin’s mammographic diagnosis. The remaining 1950 pairs are healthy pairs from whom, as from the affected pairs, information on breast cancer risk factors has been systematically collected. Among these healthy pairs are at least 200 pairs who differ with respect to each of 10 environmental risk factors for breast cancer. We expect to obtain permission from each member of 330 affected and 1365 healthy twin pairs to borrow their normal mammograms from the mammographers. We will scan each mammogram, and using a semi-computerized method of distinguishing areas of different density, we will estimate the proportion of the area of the breast image represented by densities.
 
 
 
 
 
 
 
 For the pairs in whom one twin has had breast cancer, we will compare the mammographic density from the (healthy breast) mammograms of the cases to those of the same breast of their healthy twins. This will allow us to verify the degree to which mammographic density is predictive of breast cancer. We will compare the mammographic density differences between the mammograms from the members of identical twin pairs to the differences between the mammograms from the members of female fraternal twin pairs. This will tell us whether the degree of density is a heritable factor. To assess the role played by individual environmental breast cancer risk factors, we will compare the density of mammograms from persons who have had a pertinent environmental exposure or experience to the density of the mammogram from their unexposed identical twins. This will tell us whether the exposure is likely to be related to mammographic density.