Comparison of primary and secondary breast cancers in adolescents and young adults.

BACKGROUND: Breast cancer is one of the most common cancers in adolescent and young adult (AYA) patients (ages 15-39) and may develop de novo or in patients previously treated for cancer. This study compares the demographic, tumor, treatment characteristics, and overall survival (OS) of primary versus secondary (SMN) breast cancer in female AYAs.
METHODS: All cases of invasive female AYA breast cancer in the 1998-2010 American College of Surgeons National Cancer Database were divided into 2 cohorts according to primary or secondary occurrence. Comparisons using appropriate statistical methods were performed.
RESULTS: Of 106,771 patients, 6241 (5.8%) had experienced a prior, histologically distinct malignancy. Breast SMNs were more likely ER-/PR- (OR, 1.24; 95% CI, 1.15-1.34), <1 cm (OR, 1.86; 95% CI, 1.73-1.99) tumors and present at a lower T, N (OR, 1.43; 95% CI, 1.34-1.52), and summary stage but with more distant metastases (OR, 1.42; 95% CI, 1.21-1.67) compared with primary cancers. Adjusted by stage, SMN patients underwent more total mastectomies and received less chemotherapy, radiation, and hormonal therapy. However, SMN patients received definitive surgical treatment almost twice as fast compared with primary cancers (36.12 vs 67.26 days, P < .001). Patients with SMNs had a significantly decreased 3-year OS (79% vs 88.5%, P < .001), with SMN status an independent risk factor for increased mortality (HR, 1.58; 95% CI, 1.41-1.77).
CONCLUSIONS: Nonprimary breast cancer in AYAs has different tumor characteristics, presents at a lower stage, and receives less adjuvant therapy than primary cancers. SMN status is an independent risk factor for decreased OS, with an almost 10% decrease at 3 years. Whether the outcome disparity results from previous cancer treatment or differences in biology, environment, or access to care needs further investigation.