OBJECTIVES: The APHINITY trial (NCT01358877) demonstrated a significant invasive disease-free survival improvement with PH + CT versus H + CT in patients with HER2-positive EBC at high risk of recurrence (PMID: 28581356). A previous CEA model (PMID: 30975391) used primary analysis data from APHINITY to estimate the lifetime effectiveness and costs of PH-based therapy in the United States. We developed an updated CEA model that included data from the most recent APHINITY interim analysis (8.4 years’ follow-up) to estimate PH cost effectiveness in Belgium, Spain and the Republic of Ireland (ROI). Additionally, we explore how changes in the metastatic BC (MBC) treatment landscape can impact the results of the EBC model.

METHODS: The previous Markov-based, decision-analytic (state transition) model was used. Outputs (PH + CT versus H + CT) included costs, quality-adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICERs), according to two scenarios: 1) inclusion of the updated APHINITY data; 2) inclusion of the updated APHINITY data as well as trastuzumab deruxtecan use in patients with MBC.

RESULTS: Scenario 1: Belgium (∆cost: €13,003; ∆QALY: 0.69; ICER: €18,874); Spain (∆cost: €34,042; ∆QALY: 0.50; ICER: €67,943); ROI (∆cost: €31,046; ∆QALY: 0.65; ICER: €48,097). In comparison, changes in the MBC treatment landscape (Scenario 2) resulted in a lower ICER across all three countries, with reductions ranging from –17.9% (Spain) to dominating results (Belgium).

CONCLUSIONS: These are the first CEA results published using the 8.4-year-follow-up data from APHINITY, and provide more robust evidence for the cost-effectiveness of PH in HER2-positive EBC. Adding more efficacious, but more costly, MBC treatments into the model reduced the ICER considerably in the three countries explored, highlighting the importance of optimal treatment in the early, curative setting to avoid metastasis and more costly treatments. These findings are likely to be applicable to other early oncology settings/models.