sc. administration is associated with lower administration costs. Switching patients from iv. to sc. would make it possible to treat more patients without increasing the personnel resources.

Background: Information and knowledge about cost of illness and labour productivity in patients with HER2-positive early-stage and metastatic breast cancer treated with trastuzumab is limited. The aim of this study was to estimate the direct and indirect costs associated with treatment of HER2-positive breast cancer among patients with early-stage and metastatic breast cancer, treated with trastuzumab, in a 10-year period after diagnosis. Materials and Methods: This study included all Danish HER2-positive breast cancer patients (≥18 years) treated with trastuzumab between 2005 and 2016 identified in the Danish national registers. Among this population, patients experiencing metastatic breast cancer were identified. For the study populations, we estimated total healthcare costs and indirect costs for one year prior to the breast cancer diagnosis and up to 10 years after diagnosis compared with a group of matched controls free of breast cancer.Results: We identified 4,153 HER2-positive breast cancer patients, whereof 27% were identified with metastatic breast cancer. During the follow-up period of 10 years, we estimated excess healthcare costs of EUR 115,000 among the total study population compared to controls; EUR 211,000 among patients with recurrence; and EUR 89,000 among patients without recurrence. Healthcare costs were found to be highest in the first year after diagnosis and also peaked in the year after recurrence. Labour productivity was significantly lower among patients with recurrence 10 years after breast cancer diagnosis compared with controls.Conclusions: In this study, we estimated the direct and indirect cost associated with HER2-positive breast cancer to be significantly increased during the 10 years after diagnosis, specifically among patients experiencing recurrence of breast cancer.