Long term survival of HER2-positive early breast cancer treated with trastuzumab-based adjuvant regimen: a large cohort study from clinical practice.

Trastuzumab-based regimens for the adjuvant treatment of HER2-positive early breast cancer significantly prolonged overall survival (OS) and disease free survival (DFS) in large randomized trials, with sustained benefits at four-year follow-up. We assessed long-term survival estimates and predictors in a large cohort of Italian women with early breast cancer treated with trastuzumab in clinical practice. Through a record linkage between five regional healthcare databases, we identified women treated with trastuzumab for early breast cancer in Lombardy (2006-2009). DFS and OS were estimated using the Kaplan-Meier method, and independent predictors were assessed using proportional hazard models. 2046 women received trastuzumab in early breast cancer adjuvant setting. Overall, the proportion of patients surviving free of disease was 93.9% at one year, 85.8% at 2 years, 79.4% at 3 years, and 75.0% at 4 years. OS estimates were 98.7%, 95.4%, 91.5% and 89.4% at 1, 2, 3 and 4 years, respectively. Significant independent predictors of worse survival outcomes were age <40 or ≥70 years compared to age 40-69 years, positive nodal status, radical breast surgery, combination therapy with paclitaxel, having at least one comorbidity (i.e. diabetes, cardiovascular disease), and a trastuzumab-based regimen lasting less than six months. Long term survival rates of women treated with trastuzumab for early breast cancer in clinical practice were consistent with estimates from clinical trials testing the drug in the adjuvant setting.