SMART Planning of Early-Stage Health Economic Decision Models for Mechanism-Based Precision Treatments in Rare Cancers: An Application and Tool Update.

The Systematic Model adequacy Assessment and Reporting Tool (SMART) was developed to help ensure that health decision-analytic models (DAMs) are fit for purpose, by listing key model features for which ideal modelling choices are identified. Then the user is required to report and justify any deviations from the ideal, and the consequences of these deviations for model validity and transparency. SMART can be particularly valuable in early development settings, where limited data and resources often require model simplifications. This study illustrates the application of SMART in developing model plans in such early-stage settings and examines whether updates to the tool are needed. The planned DAMs are for evaluating precision and combination treatments in two rare cancers: advanced thyroid cancer and diffuse midline glioma. Using health economic guidelines, literature, and clinical and pre-clinical expert co-author input, SMART was completed and the models were conceptualized. Deviations from ideal modelling choices included assuming homogeneous populations, adopting narrower model perspectives, omitting diagnostic pathways, and relying on simplifying assumptions. SMART highlighted these deviations, indicating a low-to-moderate impact on model validity and variable impact on transparency. Updates to SMART included refining the decision-context section, adding guiding questions and additional space for supporting resources, expanding instructions on justifying deviations and assessing their consequences, and adding a report-generating function. Using SMART enabled a systematic definition of the decision context and supported consensus between model analysts and clinical and pre-clinical experts on clear, well-justified model plans that are adequate for this resource-constrained development stage.