Racial Differences in PAM50 Subtypes in the Carolina Breast Cancer Study

Melissa A Troester, Xuezheng Sun, Emma H Allott, Joseph Geradts, Stephanie M Cohen, Chiu-Kit Tse, Erin L Kirk, Leigh B Thorne, Michelle Mathews, Yan Li, Zhiyuan Hu, Whitney R Robinson, Katherine A Hoadley, Olufunmilayo I Olopade, Katherine E Reeder-Hayes, H Shelton Earp, Andrew F Olshan, Lisa A Carey, Charles M Perou

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Background: African American breast cancer patients have lower frequency of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2 (HER2)-negative disease and higher subtype-specific mortality. Racial differences in molecular subtype within clinically defined subgroups are not well understood.

Methods: Using data and biospecimens from the population-based Carolina Breast Cancer Study (CBCS) Phase 3 (2008-2013), we classified 980 invasive breast cancers using RNA expression-based PAM50 subtype and recurrence (ROR) score that reflects proliferation and tumor size. Molecular subtypes (Luminal A, Luminal B, HER2-enriched, and Basal-like) and ROR scores (high vs low/medium) were compared by race (blacks vs whites) and age (≤50 years vs > 50 years) using chi-square tests and analysis of variance tests.

Results: Black women of all ages had a statistically significantly lower frequency of Luminal A breast cancer (25.4% and 33.6% in blacks vs 42.8% and 52.1% in whites; younger and older, respectively). All other subtype frequencies were higher in black women (case-only odds ratio [OR] = 3.11, 95% confidence interval [CI] = 2.22 to 4.37, for Basal-like; OR = 1.45, 95% CI = 1.02 to 2.06, for Luminal B; OR = 2.04, 95% CI = 1.33 to 3.13, for HER2-enriched). Among clinically HR+/HER2- cases, Luminal A subtype was less common and ROR scores were statistically significantly higher among black women.

Conclusions: Multigene assays highlight racial disparities in tumor subtype distribution that persist even in clinically defined subgroups. Differences in tumor biology (eg, HER2-enriched status) may be targetable to reduce disparities among clinically ER+/HER2- cases.

Original languageEnglish
Pages (from-to)176-182
Number of pages7
JournalJournal of the National Cancer Institute
Issue number2
Early online date01 Aug 2017
Publication statusPublished - 01 Feb 2018


  • Adult
  • African Americans
  • Aged
  • Breast Neoplasms/chemistry
  • Cell Proliferation
  • European Continental Ancestry Group
  • Female
  • Humans
  • Middle Aged
  • RNA, Neoplasm/analysis
  • Receptor, ErbB-2/analysis
  • Receptors, Estrogen/analysis
  • Receptors, Progesterone/analysis
  • Recurrence
  • Tumor Burden
  • Young Adult

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