Abstract P1-09-10: Mammographic density: Its inherent epidemiology in 12000 women from 22 diverse countries

Abstract

Abstract The International Pooling Project on Mammographic Density Consortium Background: Over the past 25 years, the epidemiologic knowledge for mammographic density (MD), as a strong marker of breast cancer risk, has expanded greatly, aided by the availability of mammograms in countries with wide-scale mammography-based breast cancer screening programs. The known epidemiology of this breast-tissue specific marker is thus that of women in high incidence countries, and not of that in countries with lifestyles that are characterized by very different life-long hormonal influences, especially during the reproductive years. The International Pooling Project on Mammography Density (IPPMD) aimed to examine the epidemiology of MD internationally, to benefit from breast cancer risk and breast cancer risk factor heterogeneity. Methods: From diverse breast cancer risk populations, IPPMD sought to include samples of 200 premenopausal and 200 postmenopausal general population women for which risk factor data and mammograms, not taken for symptomatic reasons, were available. To date we have included 11447 women from 22 countries, consisting of 40 ethnicity and location-specific population groups. 5 to 6 countries were included in each of Europe, Africa and the Middle East, Asia and the Americas. Populations not previously studied in terms of MD include South Africa, Kenya, Turkey, Egypt and Brazil. Digitized/digital films for every woman were anonymised, transferred to the study and read using Cumulus 6 by 3 readers, to obtain standardized quantitative and comparable MD estimates across the entire sample. Readers were blind to all woman and study/country identifiers. Normal errors regression models were used to analyse square root percent density and absolute dense area, after standardizing reader-specific values to a single reader's distribution. Results: All risk factor data and MD readings have recently been pooled. Initial findings are as follows. Mean percent MD and absolute dense area varied over 2-fold between the 40 population groups, after adjusting for age and BMI. There is striking consistency in several epidemiologic features of MD across all population groups, including the rate of decline of density at both pre and post-menopausal ages and the decline associated with the menopausal transition. We are exploring to what extent these and other factors such as menarche, parity, age at first birth and breastfeeding, account for between population-group differences in MD. Conclusions: This international perspective provides a valuable insight to the epidemiology of MD worldwide. Citation Format: McCormack VA. Mammographic density: Its inherent epidemiology in 12000 women from 22 diverse countries. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-09-10.