An Evaluation of an Algorithm for the Selection of Flexible Survival Models for Cancer Immunotherapies: Pass or Fail?

BACKGROUND AND OBJECTIVE: Accurately extrapolating survival beyond trial follow-up is essential in a health technology assessment where model choice often substantially impacts estimates of clinical and cost effectiveness. Evidence suggests standard parametric models often provide poor fits to long-term data from immuno-oncology trials. Palmer et al. developed an algorithm to aid the selection of more flexible survival models for these interventions. We assess the usability of the algorithm, identify areas for improvement and evaluate whether it effectively identifies models capable of accurate extrapolation. METHODS: We applied the Palmer algorithm to the CheckMate-649 trial, which investigated nivolumab plus chemotherapy versus chemotherapy alone in patients with gastroesophageal adenocarcinoma. We evaluated the algorithm's performance by comparing survival estimates from identified models using the 12-month data cut to survival observed in the 48-month data cut. RESULTS: The Palmer algorithm offers a systematic procedure for model selection, encouraging detailed analyses and ensuring that crucial stages in the selection process are not overlooked. In our study, a range of models were identified as potentially appropriate for extrapolating survival, but only flexible parametric non-mixture cure models provided extrapolations that were plausible and accurately predicted subsequently observed survival. The algorithm could be improved with minor additions around the specification of hazard plots and setting out plausibility criteria. CONCLUSIONS: The Palmer algorithm provides a systematic framework for identifying suitable survival models, and for defining plausibility criteria for extrapolation validity. Using the algorithm ensures that model selection is based on explicit justification and evidence, which could reduce discordance in health technology appraisals.

Treatment Effect Waning in Immuno-oncology Health Technology Assessments: A Review of Assumptions and Supporting Evidence with Proposals to Guide Modelling.

Treatment effect waning (TEW) refers to the attenuation of treatment effects over time. Assumptions of a sustained immuno-oncologic treatment effect have been a source of contention in health technology assessment (HTA). We review how TEW has been addressed in HTA and in the wider scientific literature. We analysed company submissions to English language HTA agencies and summarised methods and assumptions used. We subsequently reviewed TEW-related work in the ISPOR Scientific Presentations Database and conducted a targeted literature review (TLR) for evidence of the maintenance of immuno-oncology (IO) treatment effects post-treatment discontinuation. We found no standardised approach adopted by companies in submissions to HTA agencies, with immediate TEW most used in scenario analyses. Independently fitted survival models do however suggest TEW may often be implicitly modelled. Materials in the ISPOR scientific database suggest gradual TEW is more plausible than immediate TEW. The TLR uncovered evidence of durable survival in patients treated with IOs but no evidence that directly addresses the presence or absence of TEW. Our HTA review shows the need for a consistent and appropriate implementation of TEW in oncology appraisals. However, the TLR highlights the absence of direct evidence on TEW in literature, as TEW is defined in terms of relative treatment effects-not absolute survival. We propose a sequence of steps for analysts to use when assessing whether a TEW scenario is necessary and appropriate to present in appraisals of IOs.

Is single-inhaler triple therapy for COPD cost-effective in the UK? The IMPACT trial.

BACKGROUND: The IMPACT trial demonstrated superior outcomes following 52 weeks of once-daily single-inhaler treatment with fluticasone furoate (FF)/umeclidinium (UMEC)/vilanterol (VI) (100/62.5/25 µg) compared with once-daily FF/VI (100/25 µg) or UMEC/VI (62.5/25 µg). This study evaluated the cost-effectiveness of FF/UMEC/VI compared with FF/VI or UMEC/VI for the treatment of chronic obstructive pulmonary disease (COPD) from a UK National Health Service perspective. METHODS: Patient characteristics and treatment effects from IMPACT were populated into a hybrid decision tree/Markov economic model. Costs (GB£ inflated to 2018 equivalents) and health outcomes were modelled over a lifetime horizon, with a discount rate of 3.5% per annum applied to both. Sensitivity analyses were performed to test the robustness of key assumptions and input parameters. RESULTS: Compared with FF/VI and UMEC/VI, FF/UMEC/VI provided an additional 0.296 and 0.145 life years (LYs) (discounted) and 0.275 and 0.118 quality-adjusted life years (QALYs), at an additional cost of £1129 and £760, respectively. Incremental cost-effectiveness ratios (ICERs) for FF/UMEC/VI were £4104/QALY and £3809/LY gained versus FF/VI and £6418/QALY and £5225/LY gained versus UMEC/VI. At a willingness-to-pay threshold of £20 000/QALY, the probability that FF/UMEC/VI was cost-effective was 96% versus FF/VI and 74% versus UMEC/VI. Results were similar in a subgroup of patients recommended triple therapy in the 2019 National Institute for Health and Care Excellence COPD guideline. CONCLUSIONS: FF/UMEC/VI single-inhaler triple therapy improved health outcomes and was a cost-effective option compared with FF/VI or UMEC/VI for patients with symptomatic COPD and a history of exacerbations in the UK at recognised cost-effectiveness threshold levels.

Use of a flowable haemostat versus an oxidised regenerated cellulose agent in primary elective cardiac surgery: economic impact from a UK healthcare perspective.

BACKGROUND: Flowable haemostatic agents have been shown to be superior to non-flowable agents in terms of haemostatic control and need for transfusion products in patients undergoing cardiac surgery. We investigated the economic impact of the use of a flowable haemostatic agent (Floseal) compared with non-flowable oxidised regenerated cellulose (ORC) agent in primary elective cardiac surgery from the perspective of the UK National Health Service (NHS). METHODS: A cost-consequence framework based upon clinical data from a prospective trial and an observational trial and NHS-specific actual reference costs (2016) was developed to compare the economic impact of Floseal with that of ORC. The individual domains of care investigated comprised complications (major and minor) avoided, operating room time savings, surgical revisions for bleeding avoided and transfusions avoided. The cost impact of Floseal versus ORC on ICU days and extended bed days avoided was modelled separately. RESULTS: Compared with ORC, the use of Floseal would be associated with overall net savings to the NHS of £178,283 per 100 cardiac surgery patients who experience intraoperative bleeding requiring haemostatic therapy. Cost savings were apparent in all individual domains of care (complications avoided: £83,536; operating room time saved: £63,969; surgical revisions avoided: £34,038; and blood transfusions avoided: £22,317). Cost savings per 100 patients with Floseal over ORC in terms of ICU days avoided (n = 30) and extended bed days avoided (n = 51.7) were £57,960 and £21,965, respectively. A sensitivity analysis indicated that these findings remained robust when the model parameters representing the clinical benefit of Floseal over ORC were reduced by up to 20%. CONCLUSIONS: Despite higher initial acquisition costs, the use of flowable haemostatic agents achieves substantial cost savings over non-flowable agents in cardiac surgery. These cost savings commence during the operating theatre and appear to continue to be realised throughout the postoperative period.