PCN44 Cost-Effectiveness of Durvalumab Following Chemoradiotherapy in Unresectable Stage III NSCLC Patients in the US: An Update Based on 4-Year Survival Data

Abstract

Assess the effects of using 4-year time-to-event data from the PACIFIC trial in estimating the cost-effectiveness of durvalumab following chemoradiotherapy (CRT) versus CRT alone in patients with unresectable stage III NSCLC. Updated PACIFIC trial results, incorporating additional follow-up, were recently published. Four-year progression-free survival (PFS), time to progression (TTP), post-progression survival (PPS) and overall survival (OS) data from the update were added to a 3-state (progression-free, progressed, and death) state-transition (semi-Markov) model that was based on PACIFIC 3-year OS and PPS data and 2-year PFS and TTP data. Other model inputs, such as costs and utilities, remained constant for consistency when comparing outcomes. Modelling was conducted from the Medicare payer perspective over a 30-year time horizon, which was considered lifelong. The 4-year time-to-event data for the durvalumab and placebo arms in PACIFIC closely matched the original model’s extrapolated OS and PFS. For the durvalumab arm, there was a 1% difference between actual 4-year OS and PFS and values predicted using 3-year PPS and 2-year TTP and PFS data. For the placebo arm there was a difference of 5% in OS and 6% in PFS between estimates from the previous model and actual 4-year data. Durvalumab following CRT was associated with incremental quality-adjusted life year (QALY) gains of 1.65 and 1.49 QALYs in the original and updated models respectively. The original and updated ICERs for a Medicare-aged population were $55,285 and $60,692 per QALY respectively, both below a $100,000 willingness-to-pay threshold. The model was highly accurate at predicting 4-year OS and PFS in the durvalumab arm. Updated ICER estimates based on 4-year time-to-event data from PACIFIC indicate that durvalumab remains a cost-effective treatment option for patients with unresectable stage III NSCLC following chemoradiotherapy.