Association between recency of last pregnancy and biologic subtype of breast cancer.

BACKGROUND: Breast cancers (BCs) diagnosed after a recent pregnancy display features associated with poor prognosis, including hormone receptor negativity, but other tumor markers have not been examined. We sought to define the tumor marker profile of these cancers, including HER-2 and p53 expression, and examine the time interval over which this adverse profile is observed, relative to last pregnancy.
METHODS: A prospectively maintained database was reviewed to identify women with a BC diagnosis between 1998 to 2011. Parous women were categorized on the basis of the interval between pregnancy and BC diagnosis; 0-2 years, >2-5 years, >5-10 years, and >10-15 years. Tumor characteristics of parous cases were compared to those of nulliparous BC patients, who were frequency matched by age.
RESULTS: A total of 175 parous and 114 nulliparous women were identified. Women who were 0-2 years from last parity at the time of BC diagnosis were the only group who were more likely than control women to have grade 3 tumors (P<0.01), positive lymph nodes (P=0.02), and triple negative tumors (P=0.01, odds ratio 3.2, 95% confidence interval 1.2-8.5). There was no difference noted in HER-2 or p53 status relative to interval from pregnancy.
CONCLUSIONS: BC diagnosed within 2 years of pregnancy is more likely to have poor prognostic features and to be triple negative. More work is needed to delineate the time frame of pregnancy-associated BC and to define them on a molecular level, so as to devise better prevention and therapy for this devastating problem.