Breast cancer in multi-ethnic populations: the Hawaii perspective

The five major ethnic groups in Hawaii's population of 1.1 million are the Japanese, comprising 23%; Caucasians, 23%; ethnic Hawaiians, 19.9%; Filipinos, 11.3%; and Chinese, 4.8%. Only 14% of the population is foreign born. Breast cancer incidences are 29.2 per 100,000 among Filipinos, 51.3 for Japanese, 64.1 for Chinese, 104.3 for Hawaiian, and 105.6 for Caucasian women. The Caucasian incidence is similar to mainland US rates, but the incidence among Hawaii's Japanese is more than twice the rate in Japan. Japanese in Hawaii have less postmenopausal breast cancer than Caucasians, fewer axillary lymph node metastases, and a greater proportion of non-invasive tumors. Late stage at diagnosis is common among Filipino and ethnic Hawaiian woman, and their risk of death is 1.5-1.7 times that of Caucasian, Chinese, and Japanese women with the disease, even after adjustment for age, extent of disease, and socio-economic status. In the BCDDP screening study, only 20% of breast cancers detected in ethnic Hawaiians were not yet palpable and were found by mammography alone. Comparative studies of diet and estrogen levels in the ethnic groups of Hawaii and the parental populations in Japan and the West do not account for the degree of variation observed in breast cancer incidence and tumor pathology. Future research directions are suggested with a view to accounting for these differences.