6P - Pregnancy-associated breast cancer: Influence of gestation length and breastfeeding on survival in a population based cohort

Date 07 May 2015
Event IMPAKT 2015
Session Welcome reception and Poster Walk
Topics Cancer in Pregnancy
Breast Cancer
Presenter Justine Mackie
Citation Annals of Oncology (2015) 26 (suppl_3): 1-3. 10.1093/annonc/mdv113
Authors J. Mackie1, A. Ives2, M.K. Bulsara3, C. Saunders4
  • 1School Of Medicine, University of Notre Dame, 6959 - Fremantle/AU
  • 2Capcreu, University of Western Australia, 6009 - Perth/AU
  • 3Institute For Health Research, University of Notre Dame, 6959 - Fremantle/AU
  • 4Surgery, University of Western Australia, 6009 - Perth/AU



Background: Women diagnosed with pregnancy-associated breast cancer [PABC] in the first year postpartum have increased mortality compared to women whose diagnosis is not associated with pregnancy (non-PABC), or who present during pregnancy. This is not explained by diagnostic delay or tumour characteristics, but may be due to the inflammatory microenvironment of involution, or the hormonal milieu of prior pregnancy.

Aim: To investigate the influence of the duration of gestation and breastfeeding on survival in women diagnosed with PABC.

Hypothesis: Mortality is higher for women with longer gestation, and whom breastfed.

Methods: Women (15 to 44 years) in Western Australia [WA] diagnosed with breast cancer between 1 Jan 1982 and 31 Dec 2003 were identified by the WA Data Linkage System (n = 2,753). PABC affected 6.7% (n = 182). Survival data and variables were obtained from population-based health registers, and medical records. Flexible parametric and Cox's survival models were used to identify adjusted hazard ratios [HR] and 95% confidence intervals [CI]. The survival censor date was 31 May 2014.

Results: Women with postpartum-PABC (n = 129) had a 40% increased risk of death compared to non-PABC, after controlling for tumour size, histological grade, lymph node status, age and year of diagnosis (HR, 1.40; 95% CI, 1.04 to 1.90). After accounting for breastfeeding status, there remained a 67% increased risk of death only in those women who had breastfed (HR, 1.67; 95% CI, 1.08 to 2.61). There was no increase in risk of death for women who did not breastfeed (HR, 0.89; 95% CI, 0.48 to 1.65). Gestation length was not significantly associated with risk of death after controlling for prognostic variables and breastfeeding (HR 1.75, 95% CI 0.83, 3.68).

Conclusions: Breastfeeding was a highly significant prognostic factor for survival in women with postpartum-PABC.

Implications: Young women can be assured that breastfeeding is correlated with a lower risk of developing breast cancer in a women's lifetime. Postpartum-PABC is rare but clinicians should be aware of the increased mortality in this group. Future research needs to investigate the microenvironment of post-lactation breast involution.

Disclosure: All authors have declared no conflicts of interest.