Modeling the consequences of recurrences after trastuzumab treatment of HER2+ early-stage breast cancer.

Abstract

e12032 Background: The study objective was to estimate the long-term consequences of recurrences following treatment with trastuzumab (TRA) among women with HER2+ early stage breast cancer (BC) in the United States (US). Methods: A simulation model was constructed to estimate the following outcomes for each combination of hormone receptor (+/-) and nodal (+/-) status: number of recurrences, direct medical cost and indirect cost attributed to recurrences. The number of women aged ≥18 years with newly diagnosed HER2+ BC between 2018 and 2037 was estimated using SEER incidence rates (assumed constant over time) and from US Census data and accounted for the proportion of women utilizing adjuvant TRA by nodal status and age (assumed constant over time). The recurrence rate to any regional, distant or contralateral site was based on the long-term follow-up of the HERceptin Adjuvant (HERA) trial (expected 20-year recurrence proportions of 27.6% for TRA and 36.7% without TRA). Medical and pharmacy costs due to a recurrence were based on a 3-year study of metastatic BC patients treated with HER2 targeted agents. Beyond year 3, cost increased by 4.5% per year. The indirect costs of recurrences included loss of income from early retirement valued at the mean hourly wage, work absenteeism ($6,960/year), and reduced productivity while at work ($3,456/year). Non-cancer related mortality was estimated using SEER data. Results: We estimated that there would be 411,373 incident cases of early stage BC who would receive adjuvant TRA treatment from 2018 to 2037. Following each annual cohort for 20 years, we estimated that there would be 112,700 recurrences after TRA treatment and 149,674 recurrences without TRA treatment. The 20-year direct medical costs of recurrences were estimated to be $28.2 and $37.5 billion with and without TRA, respectively and the indirect costs were estimated to be $4.1 and $5.6 billion with and without TRA, respectively. Conclusions: Although TRA reduced recurrences by 25% in our 20-year model, there was a substantial number of recurrences. Future research will assess the clinical and economic impact of newer HER2 directed therapies in the adjuvant (pertuzumab, T-DM1) and extended adjuvant (neratinib) setting.