MAMMOGRAPHIC DENSITITES IN CHINESE AND CAUCASIAN WOMEN

在不同年龄的乳腺癌发病率方面，各国之间存在显著差异，但这些差异的原因尚不清楚。这项申请要求提供资源，以开展一项初步研究，以检查乳房X光照相密度--人群中乳腺癌的一个重要风险因素--是否也与人群之间乳腺癌风险的差异有关。支持这一提议的假设是，罹患乳腺癌风险较高的高加索人会有更多乳房X光检查致密的乳腺组织，这表明与风险较低的新近来到加拿大的中国移民相比，间质和上皮组织的数量更多。本研究的目的是进行一项先导性研究，以检验这一假说的可行性。我们之前没有关于乳房X光检查体积测量的数据，以估计中国女性和高加索女性之间的任何差异的大小，或这些组内的差异，以此作为计算样本量的基础。这项建议的主要目的是获得最近的中国移民(N=50)和加拿大50岁以上的高加索妇女(N=50)的总乳房组织和致密组织体积的平均值和方差的估计值，并估计这两个组之间这些测量的任何差异的大小。为了测量乳房X光摄影致密的乳腺组织的体积，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测厚仪，将其整合到乳房X光摄影过程中成像的领域中，以评估组织成分和厚度。建议的一般方法是对两组年龄在50岁或以上的女性进行横断面研究，这两组女性患乳腺癌的风险有很大差异。一群人将是高加索人，另一群最近移民到加拿大的人出生在中国。所有受试者将从安大略省乳房筛查计划(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光照片并将其数字化，并测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.