Abstract P1-07-01: Characteristics, treatment and outcomes of breast cancer diagnosed during pregnancy and the year after delivery
Authors: O'Sullivan CC , Wang Z , Zhang Z , Umbricht C , Jeter SC , Rosner GL , Stearns V , Smith KL 
Published: May 2016

Abstract
Background:
Pregnancy associated breast cancer (PABC) is defined as breast cancer (BC) diagnosed during pregnancy or during the year after delivery. Whether PABC is associated with inferior outcomes compared to non-PABC is uncertain. Data suggests characteristics and outcomes of BC diagnosed during pregnancy and BC diagnosed within the year after delivery may differ. However, most previous research has not separated BC cases diagnosed during pregnancy from those diagnosed within the year after delivery.
Methods:
We performed a single institution retrospective cohort study of women diagnosed at the Johns Hopkins Hospital with PABC between 1985-2014 and matched controls. Women with BC diagnosed during pregnancy and BC diagnosed during the year after delivery formed two separate case groups. Controls were matched 2:1 to each of the cases by time period of diagnosis, age (+/- 5 years) and extent of disease at diagnosis. Clinicopathologic features, treatment and outcomes were compared between each case group and its respective controls. Univariate Cox modeling stratified by matching set was used to compare time to relapse between cases and their matched controls.
Results:
Of 140 PABC cases identified, BC was diagnosed during pregnancy in 65 and during the year after delivery in 75. 135 controls were matched to the cases diagnosed during pregnancy and 145 controls were matched to the cases diagnosed during the year after delivery. Compared to their controls, cases diagnosed after delivery were more likely to have grade 3 tumors (81% versus 60%) and less likely to be hormone receptor (HR)-positive (62% versus 82%). Similarly, compared to their controls, cases who were pregnant at diagnosis were more likely to have grade 3 tumors (77% versus 57%) and less likely to be HR-positive (54% versus 75%). The frequency of HER2-positivity between cases diagnosed during pregnancy or during the year after delivery was similar to their respective control groups. A higher proportion of cases diagnosed during pregnancy underwent mastectomy than their controls, but this was not statistically significant (74% versus 67%). Most patients in both case groups and both control groups received chemotherapy. The proportions of patients in both case groups compared to their controls who received radiation were similar. Rates of relapse were high in the entire study population. There was a non-significant increased risk of relapse for both the cases diagnosed during pregnancy compared to their controls (HR 1.77, 95% CI 0.844-3.73, p 0.13) and for the cases diagnosed after delivery compared to their controls (HR 1.51, 95% CI 0.70-3.24, p 0.30).
Conclusions:
In our study population, women diagnosed with BC during pregnancy or within the year after delivery were more likely to have high grade and HR-negative disease than controls matched for age, extent of disease and time period of diagnosis. Rates of recurrence were high among our young study population. Findings must be interpreted with caution due to small sample size, but suggest that rates of relapse were not significantly higher among the cases diagnosed during pregnancy or within the year after delivery compared to their controls.
Citation Format: O'Sullivan CC, Wang Z, Zhang Z, Umbricht C, Jeter SC, Rosner GL, Stearns V, Smith KL. Characteristics, treatment and outcomes of breast cancer diagnosed during pregnancy and the year after delivery. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-07-01.