Association of inflammatory and noninflammatory breast cancer with socioeconomic characteristics in the Surveillance, Epidemiology, and End Results database, 2000-2007.

BACKGROUND: 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).
METHODS: 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).
RESULTS: 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)].
CONCLUSION: Overall breast cancer has been found to be positively associated with SEP, whereas in this analysis, IBC was associated with decreasing SEP. IMPACT: Studies focused on understanding the disparity in IBC incidence, as well as interventions to eliminate these differences are needed.