Methods and Progress

Contributing studies

International Pooling Project of Mammographic Density aims to pool mammography information from studies of populations with diverse breast cancer incidence rates. More than 20 studies are contributing data from 200 premenopausal and 200 postmenopausal women (age 35-69 years) from the general population. Each study is ideally providing:

  • digitized or digital anonymized mammograms for each woman
  • anonymized risk factor information (age, body mass index (BMI), age at menarche, parity, age at first birth, duration of breastfeeding, exogenous hormone use, age at menopause, family history of breast cancer, ethnicity, alcohol and tobacco consumption).

Countries included in this pooling project to date (coloured by their underlying country-level breast cancer incidence rate) are shown in the map below. The countries span populations with low (India, Saudi Arabia, South Africa, Kenya), medium (Mexico, Poland, Brazil), and high (North America, western Europe, Australia) breast cancer incidence rates (> 4-fold range in incidence rates). In addition to geographical differences, studies of migrants are included (e.g. Indian women in India and the United Kingdom, Japanese women in Japan and Hawaii, USA).


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Mammographic density readings

International studies are challenging, as there is no established automated mammographic density measurement method. First, all mammographic films will be re-read, using the Cumulus software, by a core team of four readers to provide standardized mammographic density readings. In addition, various film formats will be pooled: digitized analogue, computed radiography digital, direct digital, and both raw and processed digital images. Calibration of density readings across film types is being studied.