Timing of Presentation and Outcomes of Women with Stage IV Pregnancy-Associated Breast Cancer (PABC).

Background: Pregnancy-associated breast cancer (PABC) and concurrent, or early development of, stage IV disease is uncommon. Given this rarity, and complexities surrounding pregnancy, data are limited regarding PABC treatment and outcomes. We evaluated oncologic, obstetric, and fetal outcomes of women with stage IV PABC in relation to presentation timing and treatment.

Patients And Methods: Our retrospective review of an institutional database identified women with stage IV PABC from 1998 to 2018. PABC was defined as diagnosis during pregnancy or ≤ 1 year postpartum. Clinicopathologic, treatment, and outcome variables were compared between women diagnosed during pregnancy versus postpartum.

Results: We identified 77 women (median age 35 years; interquartile range [IQR] 32-37 years): 51 (66%) in the postpartum group and 26 (34%) in the pregnant group, including 9 with therapeutic or spontaneous abortion. Among 17 women who continued pregnancy, no obstetric or fetal complications were noted. Clinicopathologic and treatment variables did not differ between groups. Of 43 women dead from disease, 15 had triple negative (TN) tumors. Median overall survival (OS) of TN tumors was 14 months (range 5-39 months); OS was associated with hormone receptor-positive and human epidermal growth factor receptor 2 (HER2) positive tumors (p < 0.01). At 31 months (range 0-137 months) median follow-up, the 5-year OS was 34% (95% confidence interval 21-46%), and did not differ among pregnant and postpartum groups (p = 0.2).

Conclusions: Women with stage IV TN PABC had high mortality rates despite multimodality therapy. Timing of presentation did not affect management decisions or OS, even for women who completed pregnancy. Further research to understand PABC biology, focusing on TN tumors, is warranted.