Early- and late-onset breast cancer types among women in the United States and Japan.

BACKGROUND: Although differences in breast cancer incidence among Occidental and Asian populations are often attributed to variations in environmental exposures and/or lifestyle, fewer studies have systematically examined the effect of age-related variations. METHODS: To further explore age-related geographic breast cancer variations, we compared age-specific incidence patterns among cases of female invasive breast cancer from the Surveillance, Epidemiology, and End Results (SEER) program and the Osaka Cancer Registry (1978-1997). RESULTS: In SEER, there were 236,130 Whites, 21,137 Blacks, and 3,304 Japanese-Americans in Hawaii with invasive breast cancer. In Osaka, there were 25,350 cases. Incidence rates per 100,000 woman-years ranged from 87.6 among Whites to 21.8 in Osaka. Age-specific incidence rates increased rapidly until age 50 years for all race/ethnicity groups, and then continued to increase more slowly for Whites, Blacks, and Japanese-Americans in Hawaii but plateaud for Osaka. Age-specific incidence rates in SEER reflected bimodal (early-onset and late-onset) breast cancer populations, whereas Osaka had only an early-onset age distribution. These age-specific differences in incidence among SEER and Osaka persisted after adjustment for calendar-period and birth-cohort effects using age-period-cohort models. CONCLUSIONS: Results confirm striking age-specific differences among Occidental and native Japanese breast cancer populations, probably due to complex age-related biological and/or environmental variations among Occidental and Asian breast cancer populations.

Inter- and intra-ethnic differences for female breast carcinoma incidence in the continental United States and in the state of Hawaii.

BACKGROUND: Ethnic diversity is well-documented for female breast carcinoma incidence in the continental US but is not so well-established in the state of Hawaii. METHODS: Using the Surveillance, Epidemiology, and End Results (SEER) program, we analyzed n=323,607 in situ and invasive female breast cancer cases for major ethnic groups in the continental US and in Hawaii, diagnosed during the years 1992-2002. RESULTS: In the continental US, age-specific incidence rate patterns and prognostic factor profiles were good-risk for Asian or Pacific Islanders (API), intermediate for Whites, and poor-risk for Blacks. For example, early age-at-onset, high nuclear grade, aggressive histopathologic subtypes, and hormone receptor negative expression was associated with Black race in the continental US. In Hawaii, age-specific rate and prognostic profiles were more favorable for API than for White women, albeit not so striking as in the continental US. CONCLUSION: We observed inter- and intra-ethnic differences for female breast carcinoma in the continental US and in the state of Hawaii. While inter-racial disparities were expected, intra-racial differences were somewhat unexpected and possibly due to variations in racial subgroup mixing and/or cultural assimilation. For example, API women with breast carcinoma in the continental US included 96.03% Asians and 2.4% Pacific Islanders. In contrast, API women with breast carcinoma in Hawaii included 76.52% Asians and 23.46% Pacific Islanders. Moreover, APIs were more likely to be first-generation migrants in the continental US ( approximately 92%) than in Hawaii ( approximately 34%). Future studies should attempt to disaggregate racial data to separately characterize epidemiological patterns for individual ethnic groups.