International Pooling Project of Mammographic Density

描述（由申请人提供）：与脂肪组织相比，乳腺纤维腺组织比例较高的女性在随后的10年或更长时间内患乳腺癌的风险增加（高达5倍）。这种特性被称为乳房x线摄影密度（MD），在不同的女性之间有所不同，并且可能随着时间的推移在同一女性体内发生变化。由于遗传和环境因素的双重影响，MD在不同国家之间的差异可以解释乳腺癌发病率在国际上的6倍以上的差异。迄今为止，只有一项研究对此进行了调查，即美国/夏威夷/日本的比较（Maskarinec et al. 2007）。我们的目标是发起一个更广泛的乳房x线摄影密度国际汇集项目，以便：(i)汇集并获得来自跨越乳腺癌发病率范围的国家的标准化MD可比数据；（ii）描述总体和特定年龄的MD分布的国际差异，并评估这些差异是否可以用个人层面的MD危险因素来解释；（iii）量化MD的国际差异与相应的乳腺癌发病率和Pike提出的乳腺组织老化模型的关联程度；（iv）评估一系列生命危险指标（绝对/相对/特定年龄/累积）；(v)在未来继续和扩大这一汇集资源。乳房x线摄影密度国际汇集项目将是乳腺癌的第一个此类倡议，以后可以扩大到包括新的乳腺癌测量方法、成像模式和更广泛的决定因素。在国际癌症研究机构（International Agency for Research on Cancer）的领导下，我们强调从国际角度看待这一标志物，这一点尤其迫切，因为乳腺癌现在几乎在全世界每个国家都是女性最常见的癌症。如果MD确实是乳腺癌发病率的国际差异的基础，那么监测MD分布将成为乳腺癌风险变化的重要早期指标。

DESCRIPTION (provided by applicant): Women with a high percentage of fibroglandular tissue in their breast, as opposed to fatty tissue, have an increased breast cancer risk (up to 5-fold higher) in the subsequent 10 or more years. This attribute, known as mammographic density (MD), varies between women and can change within the same woman over time. Having both genetic and environmental determinants, between-country differences in MD may account for the over 6-fold international variations in breast cancer incidence rates. Only one study has investigated this to date, i.e. a US/Hawaii/Japanese comparison (Maskarinec et al. 2007). We aim to initiate a more widespread International Pooling Project of Mammographic Density to: (i) pool and obtain standardised comparable data on MD from countries spanning the breast cancer incidence range; (ii) describe international variations in overall and age-specific MD distributions and assess whether they are explained by individual-level risk factors for MD; (iii) quantify the extent to which international variations in MD correlated with corresponding breast cancer incidence rates and Pike's proposed model of breast tissue ageing; (iv) assess a range of MD metrics (absolute/relative/age-specific/cumulative); (v) continue and expand this pooled resource into the future. The International Pooling Project of Mammographic Density would be the first such initiative for MD, which could later be expanded to include new methods of MD measurement, imaging modalities and a broader range of determinants. Being led by the International Agency for Research on Cancer, we emphasize an international perspective for this marker, especially urgent as breast cancer is now the most common cancer in women in almost every country worldwide. If MD does underpin international variations in breast cancer incidence, the monitoring of MD-distributions would become an important early indicator of changes in breast cancer risk.