Treatment patterns and medical costs of metastatic breast cancer care in the United States.

Abstract

e18834 Background: Substantial advances in treatment of metastatic breast cancer (mBC) have led to changes in clinical practice and treatment costs in the United States in the past decade. We aimed to identify treatment patterns in mBC patients by subgroup and year after mBC diagnosis and associated costs from payer and societal perspectives. Methods: This study used the nationwide Flatiron Health electronic health record (EHR)-derived de-identified database (1/2011-5/2021). We excluded cases that were male, had < 6 months of follow up, no treatment data, no structured data within 90 days of diagnosis, participated in clinical trials, had non-breast invasive cancers, received therapies not used in mBC, had no data on human epidermal growth factor (HER2) and hormone receptor (HR) status. We classified patients into four subgroups: HER2-HR+, HER2+HR+, HER2+HR-, and Triple Negative (TNBC). We calculated anti-cancer and supportive drug costs at the patient level and mean costs by year after diagnosis for each subgroup. We used average wholesale prices (AWP, from McKesson Corporation) for payer perspective and Medicare prices (part B payment limit data, Part D Drug Spending Dashboard) for societal perspective. We estimated costs up to year 5 after diagnosis of mBC (< 8% received treatment after year 5). Results: 15,215 patients met the criteria (64.41% non-Hispanic White, 66.85% HER2-HR+, 18.30% HER2+HR+, 5.27% HER2+HR-, 9.58% TNBC). AWP and Medicare cost estimates by year after diagnosis and subgroup are shown in Table. 334,812 for HER2+HR+, $284,609 for HER2+HR-, $104,774 for HER2-HR+, and $54,355 for the TNBC. We observed an increase in annual costs between years 2011-2021 in most subgroups. This increase was most substantial for HER2-HR+ patients. From 2011 to 2019 (most recent complete year 1 data is for patients diagnosed in 2019), annual Medicare treatment costs in year 1 increased from $12,986 to $80,563 for HER2-HR+, $99,997 to $156,712 for HER2+HR+, and $31,397 to $53,775 for TNBC. There was no increase in costs of treating HER2+HR- in year 1, but an increase in year 2 (from $90,427 to $129,690 between 2011-2019). Conclusions: mBC treatment costs vary significantly by receptor subtype and years after diagnosis. Annual costs increased over time. Costs were greatest for HER2+ and lowest for TNBC.[Table: see text]