Comparative study of breast cancer in Mexican and Mexican-American women

Abstract

Breast cancer is the number one cause of can- cer deaths among Hispanic women in the United States, and in Mexico, it recently became the primary cause of cancer deaths. This malign- nancy represents a poorly understood and un- derstudied disease in Hispanic women. The ELLA Binational Breast Cancer Study was es- tablished in 2006 as a multi-center study to as- sess patterns of breast tumor markers, clinical characteristics, and their risk factors in women of Mexican descent. We describe the design and implementation of the ELLA Study and provide a risk factor comparison between women in the U.S. and those in Mexico based on a sample of 765 patients (364 in the U.S. and 401 in Mexico). Compared to women in Mexico, U.S. women had significantly (p < 0.05) lower parity (3.2 vs. 3.9 mean live births) and breastfeeding rates (57.5% vs. 80.5%), higher use of oral contraceptives (60.7% vs. 50.1%) and hormone replacement therapy (23.3% vs. 7.6%), and higher family history of breast cancer (15.7% vs. 9.0%). Re- sults show that differences in breast cancer risk factor patterns exist between Mexico and U.S. women. We provide lessons learned from the conduct of our study. Binational studies are an important step in understanding disease pat- terns and etiology for women in both countries.