Abstract 4914: Pregnancy and breast cancer outcomes
Authors: Choi Mihong , Han Jiyeon , Yang Bo Ram , Jang Myoung-jin , Kim Miso , Kim Tae-Yong , Im Seock-Ah , Lee Han-Byoel , Moon Hyeong-Gon , Han Wonshik , Noh Dong-Young , Lee Kyung-Hun 
Published: August 2019

Abstract
Background: Pregnancy-associated breast cancer (PABC) poses a unique challenge as hormonal changes occurring in pregnancy potentially interact with breast cancer outcomes. However, reports on prognosis of PABC have been rare and inconsistent, and most of these studies were from Western countries with only few from Asia. We investigated the outcome of PABC linking a large hospital-based database and the nationwide claims database of Korea.
Patients and methods: We retrospectively studied a cohort of 3687 female patients of reproductive age (&lt;50 years old) who had undergone surgery for breast cancer at Seoul National University Hospital from 2008 to 2015. Data on stage distribution and tumor characteristics were reviewed from the institutional database, and history of delivery or abortion from the nationwide claims database of Korea for comprehensive identification. Breast cancer during pregnancy was defined as delivery within 9 months of the diagnosis of breast cancer, and postpartum breast cancer as breast cancer diagnosis within 12 months of delivery, with both being counted as PABC.
Results: Among 3687 patients, 18 and 45 patients were classified as having breast cancer during pregnancy and postpartum breast cancer, respectively, comprising 63 cases of PABC. Patients with PABC were significantly more likely to have advanced stage and/or hormone receptor negative tumor, and be younger than 35 years old at diagnosis of breast cancer than those without it (P value for T stage, .0001; N stage, .0011; ER negativity, &lt;.0001; PR negativity, &lt;.0001; age at breast cancer diagnosis &lt;35, &lt;.0001). Similar distribution pattern of clinical characteristics was observed with postpartum breast cancer compared to their counterparts (P value for T stage, &lt;.0001; N stage, .0001; M stage, .0421; ER negativity, &lt;.0001; PR negativity, &lt;.0001; age at breast cancer diagnosis &lt;35, &lt;.0001), whereas these characteristics were comparable between patients with and without breast cancer during pregnancy. PABC and postpartum breast cancer were seemingly associated with worse survival with univariate hazard ratio (HR) of 4.53 (95% confidence interval, CI, 2.53-8.13; P value &lt;.0001) and 5.34 (95% CI, 2.91-9.82; P value &lt;.0001), multivariate HR of 1.52 (95% CI, .82-2.83; P value .1841) and 1.57 (95% CI, .82-2.99; P value .1708), respectively. Breast cancer during pregnancy was not associated with worse survival.
Conclusions: PABC and postpartum breast cancer tended to be associated with higher stage, hormone receptor negativity, and thus worse survival, but breast cancer during pregnancy had no adverse effect on survival in patients with breast cancer.
Note: This abstract was not presented at the meeting.
Citation Format: Mihong Choi, Jiyeon Han, Bo Ram Yang, Myoung-jin Jang, Miso Kim, Tae-Yong Kim, Seock-Ah Im, Han-Byoel Lee, Hyeong-Gon Moon, Wonshik Han, Dong-Young Noh, Kyung-Hun Lee. Pregnancy and breast cancer outcomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4914.