Retrospective cohort study of contralateral breast cancer risk among Asian/Pacific Islander women in the United States

While breast cancer studies often aggregate Asian/Pacific Islander (API) women as a single group, this population is heterogeneous in terms of genetic background, environmental exposures, and health-related behaviours. A retrospective cohort study evaluated the risk of contralateral breast cancer (CBC) among subgroups of adult API women with stage I-III breast cancer. Among 44,362 API women with breast cancer in the SEER registries between 2000 and 2016, 25% were Filipina, 18% were Chinese, 14% were Japanese, and 8% were Indian/Pakistani. API women as an aggregate group had increased risks of CBC (SHR 1.15; 95% CI 1.08-1.22) compared to NHW women. Chinese (SHR 1.23; 95% CI 1.08-1.40), Filipina (1.37; 1.23-1.52), and Native Hawaiian (1.69; 1.37-2.08) women had the greatest risks. The authors conclude that future research should examine inequities within the API population to design interventions that can adequately address their unique differences.