Insulin resistance contributes to racial disparities in breast cancer prognosis in US women

Emily J. Gallagher, Kezhen Fei, Sheldon M. Feldman, Elisa Port, Neil B. Friedman, Susan K. Boolbol, Brigid Killelea, Melissa Pilewskie, Lydia Choi, Tari King, Anupma Nayak, Rebeca Franco, Daliz Cruz, Irini M. Antoniou, Derek Leroith, Nina A. Bickell

Research output: Contribution to journalArticle

Abstract

Background: Racial disparities in breast cancer survival between Black and White women persist across all stages of breast cancer. The metabolic syndrome (MetS) of insulin resistance disproportionately affects more Black than White women. It has not been discerned if insulin resistance mediates the link between race and poor prognosis in breast cancer. We aimed to determine whether insulin resistance mediates in part the association between race and breast cancer prognosis, and if insulin receptor (IR) and insulin-like growth factor receptor (IGF-1R) expression differs between tumors from Black and White women. Methods: We conducted a cross-sectional, multi-center study across ten hospitals. Self-identified Black women and White women with newly diagnosed invasive breast cancer were recruited. The primary outcome was to determine if insulin resistance, which was calculated using the homeostatic model assessment of insulin resistance (HOMA-IR), mediated the effect of race on prognosis using the multivariate linear mediation model. Demographic data, anthropometric measurements, and fasting blood were collected. Poor prognosis was defined as a Nottingham Prognostic Index (NPI) > 4.4. Breast cancer pathology specimens were evaluated for IR and IGF-1R expression by immunohistochemistry (IHC). Results: Five hundred fifteen women were recruited (83% White, 17% Black). The MetS was more prevalent in Black women than in White women (40% vs 20%, p < 0.0001). HOMA-IR was higher in Black women than in White women (1.9 ± 1.2 vs 1.3 ± 1.4, p = 0.0005). Poor breast cancer prognosis was more prevalent in Black women than in White women (28% vs 15%. p = 0.004). HOMA-IR was positively associated with NPI score (r = 0.1, p = 0.02). The mediation model, adjusted for age, revealed that HOMA-IR significantly mediated the association between Black race and poor prognosis (β = 0.04, 95% CI 0.005-0.009, p = 0.002). IR expression was higher in tumors from Black women than in those from White women (79% vs 52%, p = 0.004), and greater IR/IGF-1R ratio was also associated with higher NPI score (IR/IGF-1R > 1: 4.2 ± 0.8 vs IR/IGF-1R = 1: 3.9 ± 0.8 vs IR/IGF-1R < 1: 3.5 ± 1.0, p < 0.0001). Conclusions: In this multi-center, cross-sectional study of US women with newly diagnosed invasive breast cancer, insulin resistance is one factor mediating part of the association between race and poor prognosis in breast cancer.

Original languageEnglish (US)
Article number40
JournalBreast Cancer Research
Volume22
Issue number1
DOIs
StatePublished - May 12 2020

Keywords

  • Breast cancer
  • Cross-sectional study
  • Disparities
  • Insulin receptor
  • Insulin resistance
  • Insulin-like growth factor receptor
  • Prognosis

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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  • Cite this

    Gallagher, E. J., Fei, K., Feldman, S. M., Port, E., Friedman, N. B., Boolbol, S. K., Killelea, B., Pilewskie, M., Choi, L., King, T., Nayak, A., Franco, R., Cruz, D., Antoniou, I. M., Leroith, D., & Bickell, N. A. (2020). Insulin resistance contributes to racial disparities in breast cancer prognosis in US women. Breast Cancer Research, 22(1), [40]. https://doi.org/10.1186/s13058-020-01281-y