Adverse event-related costs for systemic metastatic breast cancer treatment among female Medicaid beneficiaries.

Objective: This retrospective study compared the real-world incidence and costs of systemic treatment-related adverse events (AEs) in patients with metastatic breast cancer in a Medicaid population.

Methods: Insurance claims data for adult women who received biologic or chemotherapy (± hormonal therapy) for metastatic breast cancer between 2006-2013 were extracted from the Truven Health MarketScan Multi-State Medicaid database. Incidence of AEs (per 100 person years) and average monthly AE-related healthcare costs (per-patient-per-month) during each line of therapy (first or later lines) were estimated. The association between AEs and total all-cause healthcare costs was estimated using multivariable regression.

Results: A total of 729 metastatic breast cancer patients were analyzed. Hematological (202.3 per 100 person years) and constitutional AEs (289.6 per 100 person years) were the most common class of AEs reported. Unadjusted per-patient-per-month AE-related expenditure by class were highest for hematological AEs ($1524), followed by gastrointestinal ($839) and constitutional AEs ($795), with anemia ($942), nausea/vomiting ($699), and leukopenia/neutropenia ($550) having incurred the highest total AE-related costs. Adjusted total all-cause monthly costs increased with the number of AEs ($19,701 for >7 AEs, $16,264 for 4 - 6 AEs, and $13,731 for 1 - 3 AEs) compared to no AEs ($5908) (all p < 0.01).

Conclusions: Among metastatic breast cancer patients treated with systemic therapy in a Medicaid population, AEs were associated with significant increases in costs, which increased with the number of AEs experienced. Therapies associated with a lower incidence of AEs may reduce cost burden and improve patient outcomes.