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Background: Breast cancer is one of the top malignancies in AYA females (ages 15-39) and may develop de novo or in patients previously treated for cancer. This study compares the tumor characteristics, treatment, and overall survival (OS) of primary and secondary (SMN) breast cancers in the female AYA population. Methods: All cases of invasive AYA breast cancer contained in the 1998-2010 American College of Surgeons National Cancer Database were divided into two cohorts according to primary or secondary occurrence. Comparisons using appropriate statistical methods were performed. Results: Of 107,373 cases of invasive breast cancer, 6,241 (6.2%) had experienced a prior malignancy. Compared with cases of primary breast cancer, patients with SMNs were more often non-Hispanics (OR:1.21, CI:1.05-1.40), insured (OR:1.58, CI:1.17-2.14), and aged 35-39 (OR:1.34, CI:1.22-1.46). SMNs were more often ER- (OR:1.23, CI:1.09-1.41), PR- (OR: 1.16, CI:1.02-1.32), microcarcinomas <1cm (OR:2.08, CI:1.89-2.30) with lobular histology (OR:1.35, CI:1.15-1.57) that presented without positive lymph nodes (OR:1.38, CI:1.27-1.51) but with distant metastases (OR: 1.60, CI:1.33-1.93). Matched by stage, SMN patients underwent more total mastectomies but received less chemotherapy, radiation, or hormonal therapy. However, SMN patients received definitive surgical treatment almost twice as fast compared to primary cancers (36.12 vs. 67.26 days, p<0.001). Patients with SMNs had a significantly decreased 3-year OS (79% vs 88.5%, p<0.001) with SMN status as an independent risk factor for decreased OS (HR: 1.69, CI: 1.483-1.93). Conclusions: AYAs with non-primary breast cancer have smaller, more ER-/PR- tumors but undergo more radical surgery with less adjuvant therapy than AYA’s with primary malignancies. SMN status alone is an independent risk factor for decreased OS; AYAs with a breast SMN have almost a 10% lower 3-year OS. Whether the outcome disparity results from previous cancer treatment or differences in biology, environment, or access to care are areas needing further investigation.
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