MAMMOGRAPHIC DENSITITES IN CHINESE AND CAUCASIAN WOMEN

各国在乳腺癌的年龄别发病率方面存在显著差异，但这些差异的原因尚不清楚。这项申请要求提供资源，以开展一项试点研究，审查乳房X线摄影密度这一人口中乳腺癌的一个重要风险因素是否也与人口之间乳腺癌风险的差异有关。促使这一提议的假设是，白种人，在乳腺癌的风险较高，将有更大的乳房X线摄影致密的乳腺组织的体积，表明更多的基质和上皮组织比最近的中国移民到加拿大，在较低的风险。本研究的目的是进行一项试点研究，以检验这一假设的可行性。我们之前没有关于乳腺摄影体积测量的数据来估计中国和白人女性之间的任何差异的大小，或者这些组内的方差，以作为样本量计算的基础。本提案的主要目的是获得加拿大年龄在50岁或以上的近期中国移民（N=50）和白人女性（N=50）的总乳腺组织和致密组织体积的平均值和方差的估计值，并估计这两组之间这些测量值的任何差异的大小。为了测量乳房X光检查致密乳腺组织的体积，我们必须在受控条件下前瞻性地获取图像，我们已经开发了一种校准设备和一种厚度计，它们将被纳入乳房X光检查期间成像的区域中，以评估组织成分和厚度。提出的一般方法是对两组50岁或更大年龄的妇女进行横断面研究，这两组妇女患乳腺癌的风险有很大差异。其中一组是白人，另一组是在中国出生的新移民。所有受试者将从安大略乳腺筛查项目（OBSP）的多伦多中心招募。有关选定的风险因素和人体测量变量的信息将通过电话采访收集。将获得乳房X线照片并进行数字化，并确定乳房和致密组织的体积。

Striking differences exist between countries in the age-specific incidence of breast cancer, but the causes of these differences are unknown. This application requests resources to carry out a pilot study to examine the possibility that mammographic densities, a strong risk factor for breast cancer within the population, are also related to differences in risk of breast cancer between populations. The hypothesis that motivates this proposal is that Caucasians, at higher risk of breast cancer, will have a greater volume of mammographically dense breast tissue, indicating a greater quantity of stromal and epithelial tissue than recent Chinese migrants to Canada, at lower risk. The purpose of the study proposed here is carry out a pilot study to examine the feasibility of testing this hypothesis. We have no previous data on mammographic volumetric measures to estimate the magnitude of any difference between Chinese and Caucasian women, or of the variance within these groups, on which to base sample size calculations. The main aim of this proposal is to obtain estimates of the values of the mean and variance of the volume of total breast tissue and dense tissue in recent Chinese migrants (N=50) and Caucasian women (N=50) in Canada aged 50 years or more, and to estimate the magnitude of any difference in these measures between these two groups. To measure the volume of mammographically dense breast tissue we must acquire images prospectively under controlled conditions and we have developed a calibration device and a thickness gauge that will be incorporated into the field imaged during mammography to assess tissue composition and thickness. The general method proposed is a cross- sectional study in two groups of women aged 50 years or greater, that have greatly different risks of breast cancer. One group will be Caucasian, and the other recent migrants to Canada born in China. All subjects will be recruited from the Toronto centers of the Ontario Breast Screening Program (OBSP). Information about selected risk factors and anthropometric variables will be collected by telephone interview. Mammograms will be obtained and digitized, and the volume of the breast and of dense tissue determined.