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PP01 International pooling project of mammographic density - insights of a marker of breast cancer risk from 22 diverse countries
  1. A Burton1,
  2. I dos Santos Silva2,
  3. J Hipwell3,
  4. A Flugelman4,
  5. A Kwong5,
  6. B Peplonska6,
  7. RM Tamimi7,
  8. K Bertrand7,
  9. C Vachon8,
  10. M Hartman9,
  11. CPL Lee9,
  12. KS Chia9,
  13. C Nagata10,
  14. D Salem11,
  15. R Sirous12,
  16. G Maskarinec13,
  17. G Ursin14,
  18. C Dickens15,
  19. JW Lee16,
  20. J Kim16,
  21. G Giles17,
  22. K Krishnan17,
  23. A Pereira18,
  24. ML Garmendia18,
  25. B Perez-Gomez19,
  26. M Pollan19,
  27. M Lajous20,
  28. M Rice7,
  29. C Van Gils21,
  30. H Wanders21,
  31. S Teo22,
  32. S Mariapun22,
  33. S Vinayak23,
  34. R Ndumia23,
  35. V Ozmen24,
  36. J Stone25,
  37. J Hopper26,
  38. N Boyd27,
  39. V McCormack1
  1. 1Section of Environment and Radiation, International Agency for Research on Cancer, Lyon, France
  2. 2London School of Hygiene and Tropical Medicine, London, UK
  3. 3Centre for Medical Image Computing, University College London, London, UK
  4. 4National Cancer Control Center, Lady Davis Carmel Medical Center, Faculty of Medicine, Technion IIT, Haifa, Israel
  5. 5Division of Breast Surgery, The University of Hong Kong Faculty of Medicine, Hong Kong
  6. 6Nofer Institute of Occupational Medicine, Łódź, Poland
  7. 7Brigham and Women’s Hospital, Boston, US
  8. 8Mayo Linic, Rochester, USA
  9. 9Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore
  10. 10Department of Epidemiology and Preventive Medicine, Gifu University, Gifu, Japan
  11. 11Department of Radiology, Cairo University, Cairo, Egypt
  12. 12
  13. 13Isfahan University of Medical Science, Isfahan, Iran
  14. 14University of Hawaii Cancer Center, Honolulu, USA
  15. 15Cancer Registry of Norway, Oslo, Norway
  16. 16Department of Internal Medicine, University of the Witwatersrand, Johannesburg, South Africa
  17. 17Asan Medical Center, Seoul, Korea
  18. 18The Cancer Council Victoria, Victoria, Australia
  19. 19Instituto de Nutrición y Tecnología de Los Alimentos, Universidad de Chile, Santiago, Chile
  20. 20Environmental and Cancer Epidemiology Unit, Instituto de Salud Carlos III and CIBERESP, Madrid, Spain
  21. 21Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands
  22. 22Cancer Research Initiatives Foundation, Selangor, Malaysia
  23. 23Aga Khan University Hospital, Nairobi, Kenya
  24. 24Istanbul University, Istanbul, Turkey
  25. 25Centre for Genetic Origins of Health and Disease, University of Western Australia, Crawley, Australia
  26. 26University of Melbourne, Melbourne, Australia
  27. 27Medical Biophysics and Nutritional Sciences, University of Toronto, Toronto, Canada


Background Mammographic density (MD) is a strong intermediate risk factor for breast cancer (BC) and, having both genetic and environmental determinants, may account for the over 6-fold international variations in BC incidence rates. The International Pooling Project of Mammographic Density is a worldwide collaborative project of MD targeting populations spanning the BC incidence range. The aims of the project are to (i) describe international variations in overall and age-specific distributions of MD, (ii) assess whether international variations in MD are explained by variations in the distributions of individual-level determinants of this marker and (iii) examine whether international variations in MD correlate with corresponding BC incidence rates.

Methods Each contributing study provided comparable data on MD risk factors and mammographic images from a random sample of ˜ 400 general population women, who had undergone screening mammography. Images were transferred in digitised screen-film, full-field or computed radiography digital DICOM format (raw or processed). Images were randomly allocated into batches for MD reading using the Cumulus 6 thresholding software, by experienced readers who were blinded to study and individual-level factors. Data on MD determinants were pooled and linked with MD readings. Results are calibrated according to type of digital image (raw to processed), and adjusted for image type.

Results 22 countries and approximately 12,000 women are included, spanning populations with age-standardised BC incidence rates (ASR) of 25.8 (India) to 99 (The Netherlands) per 100,000 woman-years. To date, for 9,635 participants data have been pooled (results will be updated). The MD risk factors vary greatly across populations, for example: mean age at menarche (in years) was 14.3 (95% CI 14.1–14.5) in Korean women and 12.6 (12.5–12.8) in Mexican women; mean parity was 3.8 (3.6–4.1) in Egyptian women and 1.3 (1.1–1.4) in those from Hong Kong; and mean BMI (in kg/m2) was 33.7 (33.1–34.3) in Egyptian women compared to 22.3 (21.6–22.9) in those from India. Differences in MD according to these distributions will be presented.

Discussion The international perspective of this study generated large exposure heterogeneity enabling a wider investigation of MD determinants and the extent to which MD is an intermediate marker of BC risk, both within and between populations.

  • Mammographic Density
  • Breast Cancer

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