Long-term effect of trastuzumab on QT dispersion in adjuvant treatment for patients with Her2 receptor positive breast cancer: a pilot study.

We investigated the long-term effect of trastuzumab, a monoclonal antibody against the Her2 signalling pathway, on QT dispersion in female patients with early-stage breast cancer. A total of 46 eligible patients with early-stage breast cancer were divided into two groups according to whether they were treated with trastuzumab: Group 1 (n = 32, patients with Her2-positive tumours who were treated with trastuzumab) and Group 2 (n = 14, patients with Her2-negative tumours who were not treated with trastuzumab). The both groups were compared using QT interval measurements. Patients with breast cancer treated with trastuzumab after an anthracycline-based regimen exhibited a significantly higher QTd than non-treated patients (0.064 ± 0.023 s vs. 0.051 ± 0.016 s, respectively) (P = 0.034). The mean increases in QTd and QTcd for Group 1 patients after paclitaxel-trastuzumab combination treatment (0.021 ± 0.011 and 0.022 ± 0.014 s, respectively) are significantly different than the mean increases in QT and QTcd after an anthracycline-based regimen (0.005 ± 0.003 and 0.006 ± 0.008 s) in the same group (P = 0.0246), compared with initial measurements. It has been concluded that the relationship between increased QTd measurements and trastuzumab treatment for 12 weeks in an adjuvant setting for patients with early-stage breast cancer is independent from other study variables. We suggested that long-term treatment with trastuzumab significantly prolonged the QT interval and increased QTd in patients with breast cancer.