Higher parity and shorter breastfeeding duration: association with triple-negative phenotype of breast cancer.
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.
Shinde
Shivani S
SS
Department of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Forman
Michele R
MR
Kuerer
Henry M
HM
Yan
Kai
K
Peintinger
Florentia
F
Hunt
Kelly K
KK
Hortobagyi
Gabriel N
GN
Pusztai
Lajos
L
Symmans
W Fraser
WF
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001942:Breast Feeding; D001943:Breast Neoplasms / Q000208:ethnology / Q000209:etiology*; D005260:Female; D006801:Humans; D008572:Menarche; D008875:Middle Aged; D009376:Neoplasms, Hormone-Dependent / Q000208:ethnology / Q000209:etiology / Q000235:genetics; D010298:Parity; D010641:Phenotype; D011247:Pregnancy; D012307:Risk Factors; D013997:Time Factors