Objective: To compare breast cancer risk among young Asian and Pacific Islander (API) women to White women, all of whom were born in California during the 1960s.
Design: We used previously-collected data from a population-based case-control study in which breast cancer cases were linked to their California birth records.
Setting: California, US.
Participants: Invasive breast cancer cases diagnosed 1988-2004 among women aged < 45 were identified from the population-based California Cancer Registry. Breast cancer cases (n = 3,799) were linked to their California birth records. Controls (n = 17,461) were randomly selected from California birth records for females, frequency matched to cases by birth year.
Main outcome measures: Odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated using logistic regression.
Results: Among young women born in California, API women had higher risks of breast cancer than Whites (OR = 1.62, 95% CI: 1.35-1.94). Among APIs, the risks were highest for women of Filipina (OR = 1.72, 95% Cl: 1.15-2.56) and Japanese ancestry (OR = 1.59, 95% Cl 1.20-2.10).
Conclusions: Our finding of breast cancer risk among young API women who were born in California that exceeds that of young White women highlights the need for further evaluations of breast cancer risk among young API women and underscores the need to consider both ancestry and migration status in such evaluations.