Effect of Cardiac Dysfunction on Treatment Outcomes in Women Receiving Trastuzumab for HER2-Overexpressing Metastatic Breast Cancer

Abstract

Trastuzumab improves time to disease progression (TTP) and survival when added to chemotherapy for HERpositive metastatic breast cancer (MBC), but it is associated with infrequent cardiac dysfunction (CD). We analyzed data from a previous pivotal randomized trial of 469 women with HER2-overexpressing MBC. The aim was to determine the benefit of adding trastuzumab to chemotherapy in terms of TTP that was free of CD, including all CD, moderate or severe (New York Heart Association class III/IV) CD only, or moderate or severe CD that did not improve with cardiac therapy. We also assessed moderate or severe CD-free survival. We assessed the impact of trastuzumab for these indices on the entire cohort and on specific chemotherapy subsets. Median TTP or any CD improved when trastuzumab was added to all chemotherapy (4.6 months vs. 6.6 months with trastuzumab, P = 0.0001), an anthracycline (doxorubicin or epirubicin) plus cyclophosphamide (AC; 6.0 months vs. 6.6 months, P = 0.24), and paclitaxel (2.8 months vs. 6.6 months, P = 0.0001). When defined as time to moderate or severe CD, median TTP improved when trastuzumab was added to all chemotherapy (4.6 months vs. 7.0 months, P = 0.0001), AC (6.0 months vs. 7.2 months, P = 0.02), and paclitaxel (2.8 months vs. 6.9 months, P = 0.0001). There was no statistical difference between moderate and severe CD-free survival with trastuzumab added to chemotherapy. Outcomes improved with trastuzumab despite CD. In particular, the benefit from trastuzumab/paclitaxel outweighed the potential risk of CD in patients with MBC. These types of analyses will be critical for trials assessing trastuzumab as adjuvant therapy.