Cost-Effectiveness of Adjuvant Olaparib in Germline BRCA1/2-Mutated, High-Risk, Human Epidermal Growth Factor-2-Negative Early Breast Cancer: A Canadian Perspective

OBJECTIVES: This evaluation examined the cost-effectiveness of adjuvant olaparib versus watch and wait (W&W) in patients with germline BRCA1/2 gene mutation (gBRCAm1/2), high-risk, human epidermal growth factor-2 (HER2)-negative early breast cancer (eBC) previously treated with adjuvant or neoadjuvant chemotherapy, from a Canadian healthcare perspective.

METHODS: A five-state, semi-Markov state transition model was developed using a lifetime horizon. The target population was the intent-to-treat (‘overall’) population of the phase III randomized trial OlympiA (NCT02032823) which included patients with triple-negative (TNBC) and hormone receptor-positive (HR+) eBC. Health state transitions were modelled using data from OlympiA, supplemented with data from the OlympiAD (NCT02000622) phase III trial in gBRCAm1/2 advanced breast cancer and gBRCAm1/2-adjusted background mortality. Modelled costs included drug acquisition and administration, subsequent therapies, adverse events, hospitalization, and physician visits. Outcomes were measured in life years (LY), and quality-adjusted LYs (QALY) calculated using literature utility values. Costs and outcomes were discounted at 1.5% annually. To account for differences in future treatment and recurrence risk by HER2 status, total costs and outcomes were estimated separately for TNBC and HR+ and combined to calculate an overall population incremental cost-effectiveness ratio (ICER). Probabilistic and deterministic analyses were performed.

RESULTS: In the probabilistic base case, olaparib was associated with an additional 2.03 LYs (24.49 vs. 22.46) and 1.63 QALYs (19.41 vs. 17.77) and an incremental cost of $67,970CAD versus W&W. The ICER for olaparib was $41,597CAD per QALY gained in the probabilistic analysis, and $45,370CAD in the deterministic analysis. The probability of olaparib being cost effective at $50,000CAD per QALY gained was 66.5%. Results were consistent across HER2 subgroup and scenario analyses. Modelled outcomes were validated against OlympiA and external data.

CONCLUSIONS: Adjuvant olaparib is a cost-effective alternative to W&W in patients with gBRCAm1/2, high-risk, HER2-negative eBC, including those with TNBC and HR+, in Canada.