Epidemiology of breast cancer in a Mexican-American population.

This is a historical cohort study of breast cancer mortality in the Mexican-American community of Laredo, Texas. Included in this study were virtually all breast cancer deaths recorded in Laredo since 1875; controls matched to cases by age and birth year were drawn from the total population. Fertility history and family history of disease for cases and controls were retrieved from the genealogical data base reconstructed by our group from church and civil records for the whole city of Laredo. The findings of this study show an association between breast cancer risk and age at first birth. This study confirms familial risk to be a factor in breast cancer risk. Unlike postmenopausal breast cancer mortality in the total U.S. population, which has increased only slightly in the last 30-40 years, postmenopausal breast cancer death rates in Laredo have almost tripled since the 1940's.