Premenopausal Hormone Concentrations in a Population of Women at Very Low Risk of Breast Cancer

There are striking differences in breast cancer incidence rates between Asian and North American and Western European populations, but within Asia variation is also wide. Incidence in Mongolia is one of the lowest in the world (6.6/100,000) while China, its neighbor to the south, has about three times this rate (18.7/100,000). Furthermore, rates appear higher in urban than in rural areas in Mongolia. Over the last decade and a half Mongolia has experienced profound economic changes resulting in mass migration from a nomadic or semi-nomadic existence to a more western lifestyle in the capital city of Ulaanbaatar, and some back migration to rural areas. Together with the contrast in exposures between traditional and urban settings, migration presents the opportunity to study women as they acculturate to a more western lifestyle.

We propose collecting blood and urine samples from premenopausal Mongolian women living in UlaanBaatar, the capital of Mongolia, to describe concentrations of several steroid hormones and growth factors that play a role in breast cancer development. The purpose of the study is to assess whether endocrine profile differs by degree of Western acculturation among those who have recently migrated to the capital. Subjects will be recruited among mothers of girls participating in a study of milk consumption and hormonal status presently being conducted by our colleagues at Harvard Medical School. In addition to the blood draw and urine collection, participants will have their height and weight measured and will complete a questionnaire on reproductive and medical history, migration status and lifestyle factors. Premenopausal blood samples with accompanying information on medical history and lifestyle factors from women participating in Project Viva in Boston, Massachusetts will provide a comparison group of US women at high breast cancer risk.

In general, Asian countries have been treated as one entity and the substantial variation in breast cancer incidence among the countries that make up this large geographic area has not been addressed. This variation among Asian countries may provide further opportunity for hypothesis generating as we seek to determine what factors explain differences in breast cancer rates between populations. Studies of a range of biological parameters in premenopausal women among different racial/ethnic populations with varying breast cancer incidence would be informative.