Prognosis of breast cancer diagnosed during pregnancy and early postpartum according to immunohistochemical subtype: A matched case–control study

Purpose Pregnancy-associated breast cancer (PABC) poses a clinical challenge and its prognosis remains controversial. During the pregnancy and postpartum periods, the breast undergoes biological events that may uniquely influence disease behavior and treatment response. This study aimed to assess if a PABC diagnosis influences survival compared to non-PABC. Methods A single-center record review was performed to identify PABC patients diagnosed from January 2007 through June 2018. Two controls were matched to each PABC case by stage, immunohistochemical (IHC) subtype, age (± 3) and year of diagnosis (± 2). Disease-free survival (DFS) and overall survival (OS) were estimated with the Kaplan–Meier method and compared with the log-rank test. Multivariate analysis was used to assess the impact of PABC on outcomes. Results 125 PABC patients (pregnant: 62; postpartum: 63) and 250 controls were included. Median follow-up was 67.7 and 73.4 months, respectively. 4-year DFS was 62% in pregnant vs 78% in controls ( p = 0.010), and 63% in postpartum vs 83% in controls ( p = 0.034). Subanalysis by IHC subtype revealed a significantly inferior DFS in PABC with hormone receptor-positive/HER2-negative ( p = 0.032) and HER2-positive disease ( p = 0.005) compared to corresponding non-PABC patients. 4-year OS was similar between case groups and controls. Multivariate analysis supported the independent impact of pregnant and postpartum status on DFS ( p < 0.05). Conclusion Patients diagnosed during pregnancy and early postpartum are at high risk of recurrence. Further research is warranted to better characterize PABC tumor biology and enable the identification of novel therapeutic interventions to improve treatment outcomes.