Cost-Effectiveness Analysis of Durvalumab for Advanced Biliary Tract Cancers

We were unable to obtain specific utility values for the patients with PFS and PD status. We used data from previously published studies as the health utility of BTCs patients in PFS and PD states (0.76 for PFS and 0.68 for PD) (31 (link)). To simplify the calculation, Grade 3 or higher adverse events (≥3 AEs) with the highest incidence difference between the durvalumab plus GP and GP groups were selected. Costs were converted based on 2021 US dollar exchange rates (USD 1.0 = CNY 6.34). We only consider the direct costs associated with medication, follow-up treatment, administration, laboratory tests and major ≥3 AEs according to the TOPAZ-1 trial. We obtained the latest prices of the drugs involved in the study through the sales prices of local hospitals or by consulting local drug suppliers. The upper and lower price limits of the drugs were determined by referring to all winning bids on the national pharmaceutical data platform (www.yaozh.com). For advanced BTCs, according to China's National Basic Medical Insurance, Industrial injury insurance and maternity insurance drug catalog (32 ), durvalumab could not be covered to partially reduce patient payments. We present the prices of the relevant drugs as costs both before and after health insurance coverage in Table 1. Except for the cost of ≥3 AEs as a one-time cost input model, the costs were calculated based on the dose used in the clinical trial and on a three-week cycle. As some of the costs referred to previously published literature, we used the consumer price index (CPI) inflation calculator to adjust these costs to 2022 prices (38 ).
The drug dose was based on actual clinical trials. In the GP plus durvalumab group, the patients received 1,500 mg of durvalumab and gemcitabine (1,000 mg/m²) and cisplatin (25 mg/m²) once every 3 weeks. In the control group, the patients received gemcitabine (1,000 mg/m²) and cisplatin (25 mg/m²) once every 3 weeks. According to a report on the status of Chinese residents' nutrition and chronic diseases in 2020, the average weight of the adult Chinese population was 64.8 kg (39 ). However, considering the long progression of BTCs, most patients are likely to be middle-aged and older adults, and in the advanced stage of the disease, patients are likely to suffer from weight loss and other discomforts. Therefore, we assumed that the average weight of patients was 60 kg. The weight set would be used to calculate the drug dose per cycle for durvalumab. A total of 42.5% of patients in the durvalumab plus GP group and 49.4% in the GP group received subsequent treatments.