Abstract PR-5: Breast cancer risk factors in U.S.-born and foreign-born Hispanic women from the San Francisco Bay Area

Background: Breast cancer risk is higher in US-born Hispanics than foreign-born Hispanics and is modified by age at migration, duration of residence in the US, and acculturation. These findings suggest the importance of lifestyle factors that change following migration. We examined the risk factor profile in 1024 US-born Hispanics (UB-H) and 1509 foreign-born Hispanics (FB-H) who participated in a population-based case-control study conducted in the San Francisco Bay Area.

Methods: Breast cancer cases aged 35–79 yrs and newly diagnosed from 1995 to 2002 were identified through the Greater Bay Area Cancer Registry; controls were identified through random-digit dialing. A telephone screening interview identified 1253 cases and 1668 controls who self-reported their race/ethnicity as Hispanic or Latina. Of these, 1119 (89%) cases and 1462 (88%) controls completed an in-person interview. Associations with breast cancer risk were assessed using unconditional logistic regression.

Results: Among controls, the risk factor profile varied significantly between UB-H and FB-H. Factors associated with increased risk were more common in UB-H controls, including education (average 12 y vs. 8 y), family history of breast cancer (14% vs. 6%), menarche at age <12 yrs (32% vs. 19%), current HRT use (14% vs. 9%), height (158 cm vs. 155 cm), BMI ≥30 (44% vs. 38%), recent alcohol consumption (44% vs. 28%), and fat intake (79 vs. 68 gm/d). Factors associated with decreased risk were more common in FB-H controls, including ≥4 full-term pregnancies (30% vs. 47%), ≥24 months of breast-feeding (9% vs. 34%), ≥25 hrs/wk of lifetime total physical activity (26% vs. 31%) and fiber intake (22 vs. 31 gm/d). Even more pronounced differences were seen between 3^rd generation UB-H and recent FB-H immigrants. Thus, over time, Hispanic immigrants adopt behaviors that increase risk and give up behaviors that used to protect them against breast cancer. These changes in lifestyle are consistent with the observed increase in incidence.

Overall, associations for Hispanic women were similar to those reported in the literature for mostly non-Hispanic white women, with one exception. In both UB-H and FB-H postmenopausal women without a history of HRT use, obesity was not associated with increased risk. In both groups, strong associations were found for parity, age at first full-term pregnancy, and breast-feeding, though they were greatly attenuated after multivariate adjustment; a strong inverse association remained only for parity in UB-H. Similar associations in UB-H and FB-H were also found for current HRT use and alcohol consumption, and for BMI and premenopausal breast cancer. For several factors, associations were seen for FB-H only, including education, family history of breast cancer, personal history of benign breast disease, age at menarche, nulliparity, height, and physical activity. In FR-H, we found significant trends with dietary factors, including total calories and fat and fiber intake.

Conclusions: The associations found for FB-H are consistent with the older literature on breast cancer risk factors, which is largely based on studies in non-Hispanic white women. Associations for UB-H were less consistent. Some of the modifiable risk factors identified to date also seem important in Hispanic women, thus offering opportunities for primary prevention.