Presentation (CTI)

OBJECTIVES: Assumptions around treatment effect extrapolation are important for decision-making across National Institute for Health and Care Excellence (NICE) technology appraisals. Although this issue has been examined mainly in the context of Single Technology Appraisals for oncology indications, to our knowledge no published research has specifically explored how treatment effect extrapolation assumptions have informed NICE Highly Specialised Technologies (HST) evaluations. This study seeks to fill that gap by systematically reviewing whether and how treatment effect extrapolation has been incorporated in previous HST appraisals and informed decision-making.
METHODS: A systematic review of the documentation available for all HST topics with guidance published by April 24th 2025 was conducted. Each appraisal document for each topic was examined for references to treatment effect extrapolation or waning. Company approaches and any External Assessment Group (EAG) preferred amendments were of specific interest, as well as final implied or stated Committee-preferred approaches to treatment effect extrapolation informing decision making, and whether the final recommendation was positive. Methodological application of treatment effect assumptions within selected cost-effectiveness model structures was also of interest.
RESULTS: Thirty HST topics with published guidance were identified. In all bar one topic appraisal (HST4), the submitting company made treatment effect extrapolation assumptions beyond pivotal trial evidence of effect. Twenty-eight of the 30 included HST topics (93%) led to a positive recommendation. Scenario analyses around treatment effect extrapolation assumptions were explored in 26 appraisals (87%). In 15 appraisals (50%), available documentation implies that no waning of treatment effect was assumed over the cost-effectiveness model’s time horizon, in incremental cost-effectiveness ratio (ICER) calculations informing decision-making.
CONCLUSIONS: Treatment effect extrapolation assumptions have been essential to recommendations of HSTs through the NICE technology appraisal process to date. This research documents the assumptions used within cost-effectiveness analyses to extrapolate treatment effect and produce decision-informing cost-effectiveness results.