Higher parity and shorter breastfeeding duration: association with triple-negative phenotype of breast cancer

Cancer. 2010 Nov 1;116(21):4933-43. doi: 10.1002/cncr.25443.


Background: The combination of increased parity and shorter breastfeeding duration might increase the odds of the least differentiated triple-negative breast cancer (BC) phenotype, theoretically because an expanded progenitor cell population from each pregnancy would incompletely differentiate postpartum.

Methods: Subjects consisted of a consecutive case series of 2473 women treated for invasive breast cancer between 2001 and 2006. Breast cancer phenotype (triple-negative BC, vs non-triple-negative BC) was compared with reproductive and demographic information. Odds ratios (OR) with 95% confidence intervals (CIs) for the association of breastfeeding duration (months per child) and parity with triple-negative BC were calculated after adjusting for ethnicity, age at menarche, family history, and age at diagnosis.

Results: Compared with non-triple-negative BC, triple-negative BC was associated with shorter duration of breastfeeding per child (OR, 0.93; 95% CI, 0.90-0.97) and with higher parity (OR, 1.12; 95% CI, 1.06-1.20). By using multivariate logistic regression, triple-negative BC was independently associated with higher parity (OR, 2.76 [95% CI, 1.86-4.08] if ≥3 live births; OR, 1.89 [95% CI, 1.30-2.74] if ≤2 live births vs nulliparae), breastfeeding duration (OR, 0.55 [95% CI, 0.41-0.74] if >2 mo/child and OR, 0.58 [95% CI, 0.42-0.82] if ≤2 mo/child vs none), African American ethnicity (OR, 2.10; 95% CI, 1.52-2.92), and younger age at diagnosis (OR, 3.02 [95% CI, 2.03-4.47] if ≤40 years vs >60 years).

Conclusions: Among women with invasive breast cancer, higher parity and the absence or short duration of breastfeeding were independently associated with triple-negative BC. Any duration of breastfeeding was found to be associated with lower probability of triple-negative BC, and the odds of this phenotype decreased with increasing duration of breastfeeding.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Breast Feeding*
  • Breast Neoplasms / ethnology
  • Breast Neoplasms / etiology*
  • Female
  • Humans
  • Menarche
  • Middle Aged
  • Neoplasms, Hormone-Dependent / ethnology
  • Neoplasms, Hormone-Dependent / etiology
  • Neoplasms, Hormone-Dependent / genetics
  • Parity*
  • Phenotype
  • Pregnancy
  • Risk Factors
  • Time Factors