Breast cancer incidence in Mongolia

Data on international variation in breast cancer incidence may help to identify additional risk factors. Substantially lower breast cancer rates in Asia than in North America and Western Europe are established, but differences within Asia have been largely ignored despite heterogeneity in lifestyles and environments. Mongolia's breast cancer experience is of interest because of its shared genetics but vastly different diet compared with other parts of Asia.

Age-standardized breast cancer incidence and mortality rates obtained from the International Association of Cancer Registries are presented for several Asian countries. Mongolian incidence rates obtained from its cancer registry describe incidence within the country.

Breast cancer incidence in Mongolia (age standardized 8.0/100,000) is almost a third of rates in China (21.6/100,000), and over five times that of Japan (42.7/100,000) and Russia (43.2/100,000). Rates within Mongolia appear to have increased slightly over the last decade and are higher in urban than rural areas (annual percentage increase of age-standardized rates from 1998 to 2005 was 3.60 and 2.57 %, respectively). The increase in breast cancer incidence with age plateaus at menopause, as in other Asian populations.

Mongolia's low breast cancer incidence is of particular interest because of their unusual diet (primarily red meat and dairy) compared with other Asian countries. More intensive study of potential dietary, reproductive and lifestyle factors in Mongolia with comparison to other Asian populations may provide more clarity in what drives the international breast cancer rate differences.