Ethnic influences on hormone levels could affect breast cancer risk

Reported by Susan Aldridge, PhD, medical journalist

Ethnic variation in estrogen levels could account for differences in the risk of breast cancer.
It's already known that a woman's natural hormone levels affect her risk of developing breast cancer. Now a team at the University of Southern California reveals that levels of the hormone estrogen vary according to ethnicity and race. Maybe these variations can explain the ethnic/race factor seen in breast cancer occurrence.

Using data from the Multiethnic Cohort Study, which covered 739 women not on hormone replacement therapy, the researchers found that native Hawaiians have the highest risk of breast cancer - 65 per cent higher than whites. They also have the highest circulating levels of estrogens. Japanese Americans had the second highest breast cancer rates and the second highest estrogen levels, which seems to underline the link. This is interesting, because breast cancer rates have been on the increase among Japanese women both in the US and in Japan. It may be that lifestyle factors are impacting hormone levels, perhaps by changing age at menstruation or other hormonal events.

Latinas and whites have similar hormone profiles, but Latinas' risk of breast cancer is the lowest among the ethnic groups studied. And the estrogen/breast cancer link is not a simple one. African-Americans have a slightly lower risk of breast cancer than whites, but higher post-menopausal estrogen levels. Before menopause their risk of breast cancer is higher. Why menopause changes things for these women is a question needing further investigation.

Source
Cancer Epidemiology, Biomarkers and Prevention October 2006