Clinicopathological features and prognosis for pregnancy-associated breast cancer: A matched case-control study.

e12573 Background: Pregnancy-Associated Breast Cancer (PABC) is defined as breast cancer diagnosed during pregnancy or within 1 year postpartum. Studies indicate that PABC tends to have poorer prognostic characteristics and often worse outcomes compared to non-PABC. The primary goal of this study is to examine disease characteristics associated with PABC versus non-PABC in the United Arab Emirates (UAE), where breast cancer is characterized by a younger age and more advanced stage compared to North America and Europe. Additionally, the UAE has a younger mean age for first-time mothers and a similar age for all mothers compared to North America and Europe. Methods: Patients with PABC were selected from BC cases of women ≤40 years treated at Tawam Hospital, the largest tertiary cancer center in the UAE between January 2003 – December 2020. Each PABC patient was matched to two non-PABC patients (controls) according to cancer stage, age, and year of diagnosis. The Fisher's exact and Kruskal-Wallis tests were used to compare both study groups. Results: 66 women with PABC were identified, with a median age at diagnosis of 33.0 (interquartile range [IQR]: 30.0-37.0) years. Most presented with stage II (45.5%) or stage III (39.4%) disease and underwent mastectomy and axillary lymph node dissection. Invasive ductal carcinoma was the most frequent histological type in both groups (86.4% for PABC and 85.6% for non-PABC). PABC was associated with higher grade 3 disease compared with non- PABC (53% vs 51.5% p= 0.009). More women with PABC received neoadjuvant chemotherapy (NACT) and radiation therapy (RT) compared with non-PABC (48.5% vs 3%, p <0.001 and 80.3% vs 65.9%, p= 0.046, respectively). There were no statistically significant differences with regards to tumor size, nodal involvement, underlying histologic subtype, ER/PR expression or HER-2 status, rates of breast-conserving surgery and adjuvant chemotherapy receipt between the two groups. The median progression-free survival (PFS) was 3.2 years (IQR: 1.9-7.1) in PABC and 3.4 years (IQR: 1.2-6.2) in non-PABC group (P=0.306). The median overall survival (OS) was 4.5 years in the PABC (IQR: 2.4-7.9) versus 4.5 years (IQR: 1.9-7.9) in the non-PABC group (P = 0.786). Conclusions: PABC in women ≤40 years appears to be associated with grade III tumors and NACT and RT receipt compared to non-PABC. However, there were no significant difference in PSF and OS between PABC and non-PABC. Further analysis is underway to evaluate the prognostic factors and their effect on survival.