Health care resource utilization and costs of Medicare-enrolled patients with HR+/HER2- metastatic breast cancer treated with a CDK4/6i in the first-line setting.

Background: The introduction of cyclin-dependent kinases 4 and 6 inhibitors (CDK4/6is) has transformed the treatment landscape for patients with hormone receptor positive (HR+) and human epidermal growth factor receptor 2 negative (HER2-) metastatic breast cancer (MBC). To our knowledge, no studies have quantified health care resource utilization (HRU) or economic burden following CDK4/6i initiation in the Medicare population.

Objective: To describe HRU and quantify health care costs among Medicare-enrolled patients with HR+ HER2- MBC treated with CDK4/6is in the first-line setting.

Methods: We conducted a retrospective cohort study on Medicare-enrolled patients with HR+ HER2- MBC who initiated a CDK4/6i in the first-line setting between February 2, 2016, and December 31, 2022, using claims from the Merative MarketScan database. We examined all-cause HRU by summarizing the number of inpatient (IP), outpatient (OP), and emergency department (ED) visits as well as the length of stay during the 6 months following CDK4/6i initiation. Additionally, we assessed all-cause health care costs, including IP, OP, ED, and pharmacy, over the 1 year following CDK4/6i initiation using the Kaplan-Meier sample average estimator to account for censoring. We reported total health care costs as the sum of IP, OP, ED, and pharmacy costs.

Results: 901 patients met the inclusion criteria with a mean age of 74 years (SD = 6.84). Nearly 24% (n = 214) had an IP admission in the 6 months following CDK4/6i initiation. Among patients with an IP admission, the mean number of admissions per patient was 1.65 (SD = 0.98) with a mean length of stay per admission of 5.98 (SD = 6.25) days. Roughly 30% (n = 271) of patients had an ED visit, with a mean of 2.1 (SD = 1.54) visits per patient among those who had a visit. Most patients (n = 868, 96.44%) had an OP service, and among those with an OP service, the mean number of days with OP services was 19.96 (SD = 12.29). Mean total health care costs over the 1-year period following CDK4/6is were $62,228 (95% CI = 52,281-73,029) per patient with the main drivers being OP services ($31,686 [95% CI = 27,168-36,925]) and pharmacy costs ($22,727 [95% CI = 19,273-25,931]).

Conclusions: There are numerous sources of HRU and cost in patients following CDK4/6i initiation in the Medicare population. Patients with HR+ HER2- MBC incur high HRU, providing insights for health care decision-makers to optimize treatment strategies and resource allocation for this population.