Inflammatory breast cancer (IBC) in native Hawaiians and Pacific Islanders: Frequency of IBC and impact of socioeconomic status on survival outcomes.

Abstract

e19083 Background: IBC is one of the most aggressive types of breast cancer, accounting for only 1-4% of all breast cancer cases while causing 8-10% of breast cancer related deaths. Previous studies have demonstrated that IBC has distinct epidemiological characteristics, but the prevalence of IBC particularly in Native Hawaiian (NH) and Pacific Islander (PI) populations, and the socioeconomic disparities related to survival outcomes, are not fully understood. Our primary objective was to determine the frequency at which NH and PI breast cancer patients are diagnosed with IBC, and the association between socioeconomic status and overall survival (OS). Methods: Patients with newly-diagnosed primary invasive breast cancer were identified from January 1, 2000 through December 31, 2018 using Queen’s Medical Center Tumor Registry. Clinical T4d was used to differentiate IBC and non-IBC. OS was defined as the time from diagnosis to death or last follow-up. Patients who were alive at the date of last follow-up were censored. Univariate and multivariate cox proportional hazard models were used to assess the effects of variables of interest on OS. Results: A total of 3,715 patients were included in analysis. There were 98 (2.6%) patients with IBC and 3,617 (97.4%) with non-IBC. Proportion of IBC relative to non-IBC was significantly higher in PI (9.0%) than in White (W) (2.7%) (P < 0.001). Proportion of IBC was higher in NH (4.7%) than W but the difference was not statistically significant (P = 0.08). In multivariate analysis among the non-IBC group, OS was significantly shorter for both PI and NH than W (HR 1.72, [95%CI, 1.13-2.6]; P = 0.01, HR 1.48 [95% CI, 1.14-1.93]; P = 0.003, respectively). There were no significant racial differences seen in OS among IBC patients. Being under or uninsured was also significantly associated with short OS outcomes among patients with non-IBC but not those with IBC. Conclusions: PI have a significantly high proportion of IBC relative to non-IBC. Race and insurance status were not associated with OS in IBC although they were significantly associated with short OS in non-IBC. This result suggests that in IBC, the potential effect of racial disparity on OS is negated by the aggressive and insidious nature of the cancer. The effect of a relatively small sample size cannot be excluded, and further study in a larger population is warranted.