Cost-Effectiveness Analysis of Adjuvant Olaparib Versus Watch and Wait in the Treatment of Germline BRCA1/2-Mutated, High-Risk, HER2-Negative Early Breast Cancer in Sweden.

Introduction: This study evaluated the cost effectiveness of adjuvant olaparib versus watch and wait (WaW) in patients with germline breast cancer susceptibility gene 1/2 (gBRCA1/2)-mutated, high-risk, human epidermal growth factor receptor 2 (HER2)-negative early breast cancer (eBC), previously treated with neoadjuvant or adjuvant chemotherapy, from a Swedish healthcare perspective.

Methods: A five-state (invasive disease-free survival [IDFS], non-metastatic breast cancer [non-mBC], early-onset mBC, late-onset mBC, death) semi-Markov state transition model with a lifetime horizon was developed. Transition probabilities were informed by data from the Phase III OlympiA trial, supplemented with data from additional studies in BRCA-mutated, HER2-negative mBC. Health state utilities were derived via mapping of OlympiA data and supplemented by literature estimates. Treatment, adverse events and other medical costs were extracted from publicly available Swedish sources. Incremental cost per life-year (LY) and quality-adjusted life-year (QALY) gained were estimated. Costs and outcomes were discounted at 3% annually. One-way deterministic and probabilistic sensitivity analyses (PSA) were conducted.

Results: Over a lifetime horizon, adjuvant olaparib was associated with an additional 1.50 LYs and 1.22 QALYs, and incremental cost of 471,156 Swedish krona (SEK) versus WaW (discounted). The resulting ICER was 385,183SEK per QALY gained for olaparib versus WaW. ICERs remained below 1,000,000SEK across a range of scenarios, and were consistent across subgroups (hormone receptor [HR]-positive/HER2-negative and triple-negative breast cancer [TNBC]). In PSA, the probability of olaparib being cost effective at 1,000,000SEK per QALY was 99.8%.

Conclusions: At list price, adjuvant olaparib is a cost-effective alternative to WaW in patients with gBRCA1/2-mutated, high-risk, HER2-negative eBC in Sweden.