Abstract 3274: The impact of pregnancy on breast cancer survival: A retrospective analysis based on national data
Authors: Chuang Shu-Chun , Lin Ching-Hung , Lu Yen-Shen , Hsiung Chao A. 
Published: July 2017

Abstract
Introduction: With the increasing incidence of breast cancer in young women and the delaying first term pregnancy age, the incidence of pregnancy-associated breast cancer is expected to increase. The aim of the current study was to examine the impact of pregnancy on breast cancer survival using national registry data.
Material and Methods: The breast cancer cases were identified from the Taiwan Cancer Registry. All first primary invasive breast cancer cases diagnosed between 2002 and 2014 were identified. The study was restricted to cases who were 20-50 years old and were stage I to III diseases. Pregnancy and delivery outcomes up to 5 years before the cancer diagnoses were abstracted from the National Health Insurance database. Those who were not pregnant during this time were defined as non-pregnant cases. The data were then linked to the Taiwan national death certificate database for vital status, the causes, and the dates of death. Years of follow-up was calculated from the date of breast cancer diagnosis to the date of death or December 31, 2014. The hazard ratios (HR) and the 95% confidence intervals (CI) of the association between pregnancy and breast cancer survival were estimated using cox proportional hazard models.
Results: Among the 30,479 breast cancer cases, 90 were diagnosed during pregnancy (0.3%), 347 were diagnosed within a year after delivery (1.1%), 410 (1.3%) within 1-2 years after delivery, 1583 (5.2%) within 2-5 years after delivery, and 249 (0.8%) were pregnant after breast cancer diagnosis. By the end of 2014, 2932 cases were dead (17 cases diagnosed during pregnancy (18.9%) and 69 cases diagnosed within a year after delivery (19.9%)). The major cause of death was breast cancer (89%). Compared to non-pregnant cases (9.3% dead), the HRs were 1.91 (95% CI=1.17-3.12) for those who were diagnosed during pregnancy and 1.92 (95% CI=1.48-2.48) for those who were diagnosed within a year after delivery, adjusted for age and year of breast cancer diagnosis. After adjustment for tumor characteristics and treatment, the HR were 1.84 (HR=1.04-3.28) and 1.29 (HR=0.92-1.80) for breast cancer diagnosed during pregnancy and within a year after delivery, respectively. For those who received systemic therapy, &gt;80% of them started within 90 days. However, for subjects diagnosed during pregnancy, only 63% of them started systemic treatment within 90 days.
Conclusion: Pregnancy-associated breast cancer is associated with higher mortality compared to non-pregnant breast cancer. Adjusted for tumor characteristics and treatment attenuated the association.
Note: This abstract was not presented at the meeting.
Citation Format: Shu-Chun Chuang, Ching-Hung Lin, Yen-Shen Lu, Chao A. Hsiung. The impact of pregnancy on breast cancer survival: A retrospective analysis based on national data [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3274. doi:10.1158/1538-7445.AM2017-3274