OBJECTIVES: This retrospective study used US claims data to quantify healthcare resource use (HCRU) and costs among patients with HR+/HER2- metastatic breast cancer (mBC).

METHODS: Patients with ≥1 ICD-10 diagnosis code for BC and metastasis were identified in IQVIA PharMetrics^® Plus from 03/2019-11/2022. Selection criteria included continuous enrollment 6 months before (baseline) and ≥3 months after (follow-up) index date (earliest metastasis code), HR+/HER2- mBC treatment during follow-up, no diagnosis codes for other cancers or metastasis within 15 months pre-index, and no HER2+ or triple-negative BC treatment during follow-up. A hierarchy was used where endocrine therapy (ET) regimens were ET-only, chemotherapy (CT) included CT±ET, and targeted therapy (TT) included TT±ET/CT. Follow-up all-cause, BC-related, and clinical event of interest (CEI)-related HCRU and costs per patient per month (PPPM) were reported, overall and by treatment category. BC-related use was determined via diagnosis codes or treatments. CEI-related claims, a subset of BC-related utilization, included prophylaxis and treatment of potential adverse effects of BC therapies.

RESULTS: Among treated HR+/HER2- mBC patients (N=11,419; 98.9% female; mean±SD age, 56.6±10.4 years), the most prevalent comorbidities were obesity (17.2%), diabetes (7.7%), and chronic pulmonary disease (3.2%). Over follow-up (median [Q1,Q3], 19.0 [10.5,30.6] months), 79.4% of patients had ET, 30.6% had CT, and 23.4% had TT regimens. Most common CEIs were fatigue during ET (21.8%), gastrointestinal-related during CT (42.8%), and hematological-related during TT (42.4%). CEI-related inpatient (17.5% vs. 4.5%) and emergency department visits (8.7% vs. 1.3%) were more frequent during TT vs. ET. Mean±SD total all-cause costs PPPM were ($8,734±$9,201), of which 82.3% were BC-related and 17.8% were CEI-related. Mean±SD all-cause costs PPPM during treated follow-up were $4,161±$21,761 during ET, $15,902±$14,301 during CT, and $19,384±$12,318 during TT.

CONCLUSIONS: Numerically higher costs were observed for HR+/HER2- patients during TT. The CEI frequency may suggest an unmet need for alternative therapies.