Impact of Clinicopathologic Factors on Breast Cancer Diagnosed in Pregnancy

Effective management of breast cancer diagnosed during pregnancy (PrBC) requires the coordination of multiple specialists, including maternal fetal medicine specialists (MFM) and medical oncologists, as patients often present at a younger age with more aggressive tumor biology. It is critical to evaluate how increased time from diagnosis to treatment initiation may impact development of pregnancy complications and maternal survival outcomes.

A retrospective study was conducted to evaluate all female patients who were diagnosed with breast cancer during pregnancy across a safety-net hospital and private comprehensive cancer center from January 2015 and December 2024. Event-free survival (EFS) and overall survival (OS) were analyzed using Cox proportional hazards models adjusting for covariates including initiation of treatment during pregnancy.

Among 34 patients with PrBC, 20 (58.8%) patients received chemotherapy during pregnancy, and 19 (55.8%) patients experienced maternal or fetal complications during pregnancy. Four patients (1.8%) were diagnosed with Stage I breast cancer, 10 patients (29.4%) had Stage II disease, 12 patients (35.3%) were diagnosed with Stage III breast cancer, and 8 patients (23.5%) were diagnosed with Stage IV disease. Patients who experienced complications of pregnancy also had experienced increased time between initial biopsy to establishment with MFM compared to those without complications (p=0.03). There were no significant differences in EFS and OS among patients who did and did not initiate treatment during pregnancy nor was increased time from breast cancer diagnosis to systemic treatment initiation associated with worsened EFS or OS. Stage III and IV breast cancer diagnosis (HR 9.79; 95% CI, 1.30-76.9; p=0.03) were associated with worsened EFS; increased BMI at diagnosis was also associated with worsened OS (HR 1.30; 95% CI, 1.05-1.62; p=0.02).

While initiation of antenatal chemotherapy was not associated with improved patient outcomes, clinicopathologic factors-including increased BMI-may impact survival in PrBC. Establishment of a dedicated interdisciplinary team may improve coordination of multidisciplinary care and optimize outcomes within PrBC care.