Characteristics and treatment of human epidermal growth factor receptor 2 positive breast cancer: 43,485 cases from the National Cancer Database treated in 2010 and 2011.

BACKGROUND: Although identification of human epidermal growth factor receptor 2 (Her2) positive breast cancer represents one of the greatest advances over the past 3 decades, it has not been studied extensively on a national level.

METHODS: The National Cancer Database is a joint project of the American Cancer Society and the American College of Surgeons and contains data on about 70% of the cancer cases in the United States. Data on Her2 have been collected since 2010 and was used for this study.

RESULTS: Of 298,937 cases of invasive breast cancer with known Her2 status diagnosed in 2010 and 2011, 43,485 (14.5%) were Her2 positive. Her2 positivity was greatest in Asian/Pacific Islanders and least in non-Hispanic Whites and was markedly more common in younger women. The incidence of Her2 positive tumors ranged from a low of 13.9% in the Mountain West region to a high of 16.0% in the West South Central region (P < .001). Compared with Her2 negative tumors, Her2 positive tumors were larger (2.6 vs 2.2 cm, P < .001), more likely to have positive nodes (39% vs 31% P < .001), have lymphovascular invasion (30% vs 20%, P < .001), and be high grade (56% vs 29%, P < .001). There were also differences by histology: invasive ductal 16.4%, invasive lobular 5.5%, tubular 2.3%, inflammatory 36%, and Paget's with invasion 59%. When adjusted for age, race, tumor size, and nodal status Her2 positive tumors were much more likely to receive chemotherapy (odds ratio = 5.5, confidence interval = 5.2 to 6.0) and somewhat less likely to undergo breast preservation (odds ratio = .78, confidence interval = .76 to .80).

CONCLUSIONS: Her2 positive tumors have distinct epidemiologic, clinical, and treatment characteristics.