Patient out-of-pocket savings with lower-dose trastuzumab.

Abstract

e18828 Background: Trastuzumab-related costs of human epidermal growth factor receptor 2 (HER2) positive breast cancer treatment are significant, approaching $70,000 per patient in the adjuvant setting alone. Recently developed population pharmacokinetic models demonstrate that therapeutic levels of trastuzumab are maintained despite decreased maintenance dose or dose frequency, potentially improving trastuzumab’s value proposition. In this observational study, we evaluate the potential patient- and health system-level financial implications of low-dose trastuzumab. Methods: We identified 196 individuals who received treatment for HER2-positive breast cancer with trastuzumab or its biosimilars at a single urban comprehensive cancer center between January 1, 2017 and October 31, 2019. We estimate, using publicly available information, patient-experienced out-of-pocket costs using deterministic modeling under different conditions corresponding to changes in dosing practices, geographic site of trastuzumab administration, patient employment status, intent of treatment, and billing procedures, as well as Medicare cost-savings estimates. Results: Both reducing the maintenance dose of trastuzumab from the FDA-labeled dose of 6 mg/kg to 4 mg/kg Q3W and reducing maintenance dose frequency of trastuzumab from 6 mg/kg Q3W to Q4W were each associated with significant patient savings on drug- and administration-related out-of-pocket costs. Depending on billing practice and clinical scenario, patient savings as a percentage of total costs were 9-20% (neoadjuvant), 17-22% (adjuvant), and 14-19% (metastatic) with 6 mg/kg Q4W dosing. Similarly, 4 mg/kg Q3W dosing had savings of 15-25% (neoadjuvant), 19-28% (adjuvant), and 13-28% (metastatic). Utilization of off-label dosing regimens could result in $2.69 billion USD in annual Medicare spending on trastuzumab, an estimated savings of $670-810 million USD. Conclusions: Meaningful patient-level and system-level financial savings in the treatment of HER2-positive breast cancer can be achieved using pharmacokinetically near-equivalent low-dose or reduced frequency maintenance trastuzumab dosing. Given the significant potential savings, further prospective studies aimed at reducing dose or frequency of monoclonal antibodies in the treatment of cancer are warranted.