About the Study

The International Pooling Project of Mammographic Density will examine variations in mammographic density across populations, through collection and analysis of individual level risk factor data and mammograms from general population studies conducted worldwide.

Mammographic density is typically measured as the absolute area or percentage of breast tissue that appears radiodense (white) on a mammogram. Fibroglandular tissue appears radiodense on a mammogram (as opposed to fatty tissue, which appears black). Mammographic density is one of the strongest markers of subsequent breast cancer risk, although its presence reduces the sensitivity of screening for breast cancer by mammography.

The epidemiology of mammographic density has revealed both lifestyle and genetic determinants. Many of the lifestyle determinants are consistent with breast cancer risk factors, prompting the question of whether the more than 6-fold international variations in breast cancer incidence rates may be explained by differences in population-level mammographic density distributions.

The overall aims of the project are to:

  1. pool and obtain standardized, comparable data on mammographic density from countries spanning the entire range of breast cancer incidence;

  2. describe international variations by overall and age-specific distributions of mammographic density metrics (absolute/relative/age-specific/cumulative) and assess whether they are explained by individual-level risk factors for mammographic density;

  3. quantify the extent to which international variations in mammographic density correlate with corresponding breast cancer incidence rates and Pike’s model of breast tissue ageing;

  4. develop and expand this project in the future as a reference database for mammographic density worldwide.

The International Pooling Project of Mammographic Density is the first worldwide initiative for mammographic density data. The study is funded by the United States National Cancer Institute (R03CA167771-01) and has been approved by the International Agency for Research on Cancer (IARC) Ethics Committee (IEC).