Association of Inflammatory and Noninflammatory Breast Cancer with Socioeconomic Characteristics in the Surveillance, Epidemiology, and End Results Database, 2000–2007

Abstract

Inflammatory breast cancer (IBC) is a rare and highly aggressive form of primary breast cancer. Little is known about the risk factors for IBC, specifically the association with socioeconomic position (SEP). The association between breast cancer type (IBC vs. non-IBC) with county-level SEP in the Surveillance, Epidemiology, and End Results database for cases diagnosed from 2000 to 2007 was examined. County-level SEP characteristics included metropolitan versus non-metropolitan residence, percentage below the poverty level, percentage less than high-school graduate, and an index combining the poverty and high-school variables. IBC and non-IBC age-adjusted incidence rates were calculated, stratified on SEP and race/ethnicity. The odds of IBC versus non-IBC given a particular SEP characteristic, adjusting for age and race/ethnicity, was examined through fitting of hierarchical logistic regression models (HLM). Incidence rates for IBC generally increased as SEP decreased, whereas the opposite was found for non-IBC. HLM results showed that low SEP is associated with higher odds of IBC: highest (≥ 20%) versus lowest (<10%) persons below the poverty level [OR (95% confidence interval, CI) = 1.25 (1.09-1.43)]; highest (>28.76%) versus lowest (≤ 15.99%) persons less than high-school graduate [OR (95% CI) = 1.25 (1.10-1.42)]; and low SEP as measured by poverty-high school index versus high SEP [OR (95% CI)= 1.26 (1.11-1.44)]. Overall breast cancer has been found to be positively associated with SEP, whereas in this analysis, IBC was associated with decreasing SEP. Studies focused on understanding the disparity in IBC incidence, as well as interventions to eliminate these differences are needed.