Breastfeeding, PAM50 Tumor Subtype, and Breast Cancer Prognosis and Survival

Marilyn L. Kwan, Philip S. Bernard, Candyce H. Kroenke, Rachel E. Factor, Laurel A. Habel, Erin K. Weltzien, Adrienne Castillo, Erica P. Gunderson, Kaylynn S. Maxfield, Inge J. Stijleman, Bryan M. Langholz, Charles P. Quesenberry, Lawrence H. Kushi, Carol Sweeney, Bette J. Caan

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

Background: Breastfeeding is associated with decreased breast cancer risk, yet associations with prognosis and survival by tumor subtype are largely unknown. Methods: We conducted a cohort study of 1636 women from two prospective breast cancer cohorts. Intrinsic tumor subtype (luminal A, luminal B, human epidermal growth factor receptor 2 [HER2]-enriched, basal-like) was determined by the PAM50 gene expression assay. Breastfeeding history was obtained from participant questionnaires. Questionnaires and medical record reviews documented 383 recurrences and 290 breast cancer deaths during a median follow-up of nine years. Multinomial logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) between breastfeeding and tumor subtype. Cox regression was used to estimate hazard ratios (HRs) for breast cancer recurrence or death. Statistical significance tests were two-sided. Results: Breast cancer patients with basal-like tumors were less likely to have previously breastfed than those with luminal A tumors (OR = 0.56, 95% CI = 0.39 to 0.80). Among all patients, ever breastfeeding was associated with decreased risk of recurrence (HR = 0.70, 95% CI = 0.53 to 0.93), especially breastfeeding for six months or more (HR = 0.63, 95% CI = 0.46 to 0.87, P <inf>trend</inf> =. 01). Similar associations were observed for breast cancer death. Among women with luminal A subtype, ever breastfeeding was associated with decreased risks of recurrence (HR = 0.52, 95% CI = 0.31 to 0.89) and breast cancer death (HR = 0.52, 95% CI = 0.29 to 0.93), yet no statistically significant associations were observed among the other subtypes. Effects appeared to be limited to tumors with lower expression of proliferation genes. Conclusions: History of breastfeeding might affect prognosis and survival by establishing a luminal tumor environment with lower proliferative activity.

Original languageEnglish (US)
Article numberdjv087
JournalJournal of the National Cancer Institute
Volume107
Issue number7
DOIs
StatePublished - Jul 1 2015
Externally publishedYes

ASJC Scopus subject areas

  • Cancer Research
  • Oncology

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