Objective: To evaluate reproductive history risk factors in breast cancer among Hispanic (HISP) women in the U.S. southwest, a population with approximately 33% lower breast cancer incidence than non-Hispanic whites (NHW).
Methods: Population-based case-control study of HISP (796 cases, 919 controls) and NHW (1,525 cases, 1,596 controls) women.
Results: 19.3% of HISP women reported five or more births and had a reduced risk of breast cancer, adjusted odds ratio (OR) 0.70 (95% confidence interval (CI): 0.50, 0.98) compared to those with one or two births. Breast cancer risk for HISP increased with older age at first birth, p trend = 0.008. Parity and age at first birth associations were specific to ER positive tumors. HISP women who had given birth within five years had higher breast cancer risk than women with 16-25 years since a birth, OR 2.62 (95% CI: 1.44, 4.78); the trend with years since last birth was stronger than for NHWs, p interaction = 0.05.
Conclusions: Reproductive history influences on breast cancer risk among HISP were similar to associations reported for NHWs. Differences in the prevalence of reproductive risk factors would explain an estimated 6.6% lower breast cancer incidence for HISP compared to NHWs.