Breast cancer in Maori and non-Maori women.

ABSTRACT

PIP: National statistics collected in New Zealand since the mid-1960s have identified higher rates of breast cancer in Maori women under 40 years of age than their non-Maori counterparts, despite their low socioeconomic status and high fertility. Data from a nationwide population-based case-control study of breast cancer in New Zealand women 25-54 years of age were used to compare the age-adjusted distribution of reproductive and other risk factors for breast cancer in self-identified Maori (n = 89) and non-Maori women (n = 1771) from the control group. Compared with women with no Maori ancestors, women 25-39 years old with at least half Maori ancestry had a two-fold higher risk of breast cancer after adjustment for known risk factors (odds ratio, 2.2; 95% confidence interval, 1.2-4.2). However, when data from the control group were analyzed, Maori women had a significantly more favorable profile in terms of breast cancer risk than their non-Maori counterparts in terms of education level, socioeconomic status, age at first full-term pregnancy, parity, and duration of breast feeding. The only exception to this pattern was body mass index. 62.1% of Maori controls 25-54 years old, compared with 23.1% of their non-Maori counterparts, were in the highest quartile of recent body mass index (p 0.001). The excess of breast cancer in young Maori may reflect unknown genetic factors that increase susceptibility.