Variation in Inflammatory and Early Onset Breast Cancer Incidence and Survival by Geography, Socioeconomic Position, and Tumor Characteristics.

Abstract

Inflammatory and young-onset breast cancers are relatively rare and have a poor prognosis. The first two projects of this dissertation utilize the United States (US) Surveillance, Epidemiology, and End Results (SEER) database to examine inflammatory breast cancer (IBC) incidence and survival by county level socioeconomic position (SEP) in order to help elucidate potential risk and prognostic factors for this aggressive form of breast cancer. A number of studies have suggested a young-onset, rapidly progressing form of breast cancer may be more common in North Africa. However, little research exists examining the characteristics of breast cancer in this region. The third project of this dissertation is an age-stratified comparison of breast cancer characteristics between Egypt and the US using the Gharbiah, Egypt population based cancer registry (GCR) and the US SEER database. While overall breast cancer has been found to be positively associated with SEP, in this dissertation’s first project, IBC was associated with decreasing county-level SEP. Incidence rates for IBC generally increased as SEP decreased, while the opposite was found for non-IBC. Hierarchical logistic regression models showed Black, American Indian/Alaska Native, Hispanic White race/ethnicity, low county-level SEP, and younger age are associated with higher odds of IBC. In this dissertation’s second project, the Kaplan-Meier survival analysis showed that IBC has worse survival than non-IBC. Residing in a lower SEP, rural county significantly lowers survival for non-IBC in multivariate proportional hazards models. Subjects of Black race/ethnicity appear to have worse survival regardless of BC type, stage, county-level SEP, tumor, or treatment characteristics. This dissertation’s third project identified significant in age at diagnosis, tumor grade, hormone receptor status, histology, and stage differences between Egyptian and US breast cancer cases. These differences persisted in age-stratified and multivariate analysis. Egyptian cases were on average younger and were more likely to have tumors that were hormone receptor negative, ductal histology, and diagnosed at higher stage in multivariate models, though the majority of Egyptian tumors were grade II. These differences in tumor and patient characteristics held in age-stratified analysis.