Impact of Her‐2‐Targeted Therapy on Overall Survival in Patients With Her‐2 Positive Metastatic Breast Cancer

Upon disease progression on trastuzumab‐based therapy, patients with HER‐2 positive metastatic breast cancer (MBC) may switch to lapatinib or continue on trastuzumab. We aimed to assess the impact of both strategies on overall survival (OS) in all patients treated for HER‐2 positive MBC at the Medical University Vienna from 1999 until 2009. A total of 201 patients were identified from a breast cancer data base. Of these 115 (57.2%) received multiple lines of trastuzumab‐based therapy, whereas 58 (28.9%) were treated with a single line. A control group of 28 patients (13.9%) had never received trastuzumab as they were treated before 1999, when trastuzumab was registered. OS from diagnosis of metastatic disease was defined as primary study endpoint. Trastuzumab significantly prolonged OS in HER‐2 positive MBC (41 versus 13 months; p < 0.001). Administration of multiple lines further improved OS; this, however, did not reach statistical significance (47 versus 28 months; p = 0.069). Positive estrogen receptor (ER) status (HR 1.6; 95% CI 1.13–2.27) was associated with better outcome compared to negative estrogen receptor status (p = 0.02). Addition of lapatinib did not improve OS significantly in patients with prior trastuzumab‐based therapy (62 versus 47 months; p = n.s.). Patients receiving lapatinib after diagnosis of BM, however, experienced an improvement of OS (22 versus 5 months; p = 0.022). Trastuzumab improves OS in patients with HER‐2 positive MBC with further nonsignificant improvement when administered in multiple lines. Lapatinib did not further improve OS in the entire population; however, lapatinib might improve OS in patients with BM.