Study Populations

This study cohort consisted of all female patients from CCR who 1) were diagnosed in California, 2) between January 1, 1988, and December 31, 2013, 3) with a primary breast cancer, 4) were younger than age 100 years at diagnosis, 5) had an available social security number (SSN), 6) were part of the three population groups of interest (first-generation ME immigrants, second- or subsequent-generation ME immigrants, and NHW), and 7) had a known breast cancer stage at diagnosis.

The three population groups of interest in this study were first-generation ME immigrants, second- or subsequent-generation ME immigrants, and NHW. If the patient had a Middle Eastern last name (25), did not have a Hispanic or Asian last name, and was born in one of the Middle Eastern countries, she was considered a first-generation ME immigrant. If the patient had a Middle Eastern last name (25), did not have a Hispanic or Asian last name, was not born in one of the Middle Eastern countries, and did not have a missing birth country, she was considered a second- or subsequent-generation ME immigrant. Finally, if the patient did not have an ME or Hispanic or Asian last name and was identified as white in the CCR data set, she was considered NHW in our analysis.