Treatment Patterns, Clinical Events, and Costs of Care for Patients With Triple Negative Metastatic Breast Cancer: A Retrospective US Claims Database Study.

Background: Chemotherapy is the main treatment for patients with metastatic triple-negative breast cancer (mTNBC) who are ineligible for immunotherapy. TNBC is associated with poorer treatment outcomes than other breast cancer subtypes. Objective: To evaluate treatment patterns, quantify real-world healthcare costs and assess the burden of clinical events of interest (CEIs) among US patients with mTNBC who did not receive immunotherapy. Methods: This retrospective study used IQVIA PharMetrics® Plus healthcare claims data. Treatment-based proxies were used to identify patients first diagnosed with mTNBC from March 2017 to September 2023. Treatment regimens, frequency and incidence of CEIs, and all-cause, breast cancer-related, and CEI-related costs per patient per month (PPPM, including drug costs) were described during overall follow-up (any line of therapy [LOT]) and during LOT1 and LOT2. Results: A total of 2717 patients with mTNBC (99.1% female; mean±SD age, 55.6 ± 10.7 years) were identified. Over the follow-up period (median [Q1,Q3], 11.7 [6.0, 26.5] months), most patients (73.1%) only reached LOT1, and the remaining 26.9% of patients had multiple LOTs. Most patients had chemotherapy in LOT1 (98.1%) and LOT2 (90.6%); 98.5% had chemotherapy across any LOTs. Taxanes were the most common, observed in 74.8% of the overall cohort, followed by anthracyclines (56.4%). Across any LOT, 76.1% of patients had ≥1 CEI, most commonly hematological (49.5%), gastrointestinal (44.3%), infusion-related reactions (31.2%), and fatigue (27.8%). Mean (SD) all-cause total costs PPPM were Discussion: Our study findings confirm previously reported high economic burden of mTNBC, with about 80% related to BC treatment. Most patients experienced CEIs during treatment, and these accounted for one-third of their total healthcare costs. Conclusions: Our study focused on patients with mTNBC with the greatest unmet need, namely those ineligible for immunotherapy. In patients with mTNBC, most of whom received chemotherapy as standard of care, CEIs presented both a clinical and economic burden, highlighting the need for newer treatments that balance total costs of care with adverse events and clinical benefit.