Birth Characteristics and Breast Cancer in Young Women
Currently, only about 50% of breast cancer diagnoses can be explained by known risk factors. Most of these risk factors are related to exposures to estrogens during adult life. Very little, however, is known about how factors experienced earlier in life affect later breast cancer risk. Recently, one line of inquiry has focused on the role that prenatal exposures to maternal estrogens may play in breast cancer etiology. During fetal development, when in-utero estrogen levels can be several-fold higher than those experienced during normal non-pregnant adult life, mammary tissue undergoes rapid cellular proliferation making it especially susceptible to environmental insults. Another burgeoning area of interest is the influence of socioeconomic status (SES) and geographic location on breast cancer risk. While both adult SES and geographic location are well-established predictors of breast cancer risk, they are not well understood. Similar to other known breast cancer risk factors, almost nothing is known about how these factors experienced during early life affect subsequent risk of breast cancer. This study is designed to test the hypothesis that selected pre- and peri-natal factors are related to subsequent breast cancer risk in young California-born women. The specific aims of this study are to: 1) evaluate the relationship between breast cancer risk and selected birth characteristics, including maternal and paternal age, maternal pregnancy complications, twinning, birth order, infant birth weight and length, gestational age at birth, and paternal occupation; 2) evaluate birth characteristics in the context of area-level socioeconomic (SES) indicators derived from U.S. Census data (SES will be examined both as an independent and potential mediating factor to the other early-life factors examined); and 3) evaluate birth characteristics in the context of region of birth. Region of birth (San Francisco Bay, South Coast, remainder of state) will be examined both as an independent and potential mediating factor to the other early-life factors examined. This is a case control analysis. All cases of invasive breast cancer diagnosed in California 1988-2002 among women born 1960 or later will be identified from the California Cancer Registry. One set of controls will consist of two randomly selected live born females born in the same year in California as the matched case. The other control group will consist of other non-hormonally and non-smoking related cancers matched to cases (2:1) on sex, year of birth and year of diagnosis. Cases and controls will be linked to their birth records and data on birth characteristics and maternal address at birth will be extracted from their birth records. Using historical U.S. Census data, neighborhood SES and region at birth will be assigned to all study subjects. Conditional logistic regression models will be used to calculate age- and race-adjusted odds ratios for each of the pre- and peri-natal factors investigated. Breast cancer in young women tends to be especially aggressive, is most common in African American women, and is not well understood. Furthermore, very little is known about the pre- and peri-natal origins of breast cancer. To our knowledge, this study is the first of its kind to incorporate early life environmental factors such as SES and region of birth with a study of prenatal factors and breast cancer among young women. In doing so, it offers the opportunity to increase our understanding of breast cancer etiology, which is fundamental to our efforts to prevent and control this disease.
Principal Investigators: Peggy Reynolds, Ph.D.
Co-Investigator: Rudy Rull, Ph.D.
Funding: California Breast Cancer Research Program
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