Reducing Opioid Use for Chronic Pain With a Group-Based Intervention: Cost-Effectiveness Analysis Using Data from the I-WOTCH Randomised Controlled Trial

Background and aims: Long-term strong opioid use for chronic non-malignant pain (CNMP) represents a significant public health challenge, associated with reduced healthrelated quality of life (HRQoL) and increased mortality.The Improving the Wellbeing of people with Opioid Treated CHronic pain (I-WOTCH) trial demonstrated that a multicomponent intervention supporting opioid withdrawal in people with CNMP successfully reduced opioid consumption compared with best usual care (BUC), without adversely affecting perceived pain levels.This study aimed to assess the value-for-money of the strategies tested in the I-WOTCH trial, from the perspective of the United Kingdom National Health Service (NHS) and Personal and Social Services.Design, setting and participants: Within-trial cost-consequence (CCA) and model-based cost-effectiveness analyses (CEA), over one year and lifetime horizons, respectively.Data were sourced from the I-WOTCH trial, which recruited 608 participants from 191 primary care centres in England between May 2017 and January 2019 and followed them up for up to 12 months.Participants received either BUC or 3 group sessions (lasting one day each) led by a trained intervention nurse and by a lay person with CNMP and lived experience with opioid tapering.These sessions, designed to develop selfmanagement skills, were supplemented by ongoing one-to-one support from nursing and lay personnel during follow-up.We used a probabilistic state-transition model to predict expected quality-adjusted life years (QALYs) and costs (in UK £) of each strategy over the lifetime of an individual.Model input parameters were derived mostly from the I-WOTCH trial.Opioid-related excess mortality and fracture rates were extracted from the literature.Measurements: Individual-level healthcare resource use and generic HRQoL [measured using the EuroQOL five dimensions questionnaire (Equation 5D)] were collected at baseline, 4, 8 and 12 months, and analysed to estimate total costs and health consequences for the I-WOTCH and BUC groups.