Long-term safety of trastuzumab in patients with HER2-positive breast cancer

Patients with HER2-positive breast cancer receive one year of trastuzumab as
part of optimal standard adjuvant systemic therapy. The addition of trastuzumab
to the standard adjuvant chemotherapy in HER2-positive breast cancer patients
markedly improves treatment outcome. Short-term side effects of trastuzumab
treatment are mild and mostly treatable. Few long-term data are available of
trastuzumab tolerability. In this study we want to recruit long-term breast
cancer survivors after adjuvant trastuzumab treatment to participate in a late
tolerability study, to determine long-term effects after trastuzumab treatment
to added co morbidity over time.

Primary objective
• To explore changes in left ventricular ejection fraction (LVEF) values
before, during and after trastuzumab treatment

Secondary objectives
• To explore the reversibility of congestive heart failure associated with
trastuzumab treatment
• To determine the relation between *Brain Natriuretic Peptide* (NT-proBNP),
troponin T blood levels and changes in left ventricular ejection fractions
(LVEF) after trastuzumab treatment
• To determine genetic variability in relevant known single nucleotide
polymorphisms [SNPs] in the extracellular-, transmembrane and intracellular
domain

Retrospective part (period before and during trastuzumab treatment) and a
prospective part (period after trastuzumab treatment) of the study

Three hospital visits will be done during the first- and during the second
study period. In one session five tubes of 5 ml blood will be taken for
haematological, chemistry and genotype analysis. The following assessments will
be performed; MUGA scan and electrocardiogram.