OBJECTIVES: To explore considerations unique to health economic modelling in a crowded treatment landscape and provide recommendations for addressing these considerations.

METHODS: Three disease areas with several available treatments were chosen as case studies: moderate-to-severe psoriasis, active psoriatic arthritis, and moderately-to-severely active ulcerative colitis. Within each area, five of the most recent health technology assessments (HTAs) from the UK, Canada, Australia, and the US were reviewed for considerations unique to modelling in a crowded treatment landscape. Data were extracted and themes were identified across the included HTAs.

RESULTS: All reviewed HTAs were highly affected by the large number of pre-existing treatments in the disease area. All models (15/15) replicated the model structure of earlier treatments and most followed earlier approaches to utility and cost estimates (9/15), with the remainder taking a cost-comparison approach (6/15). HTA bodies frequently scrutinised areas of uncertainty unique to crowded landscapes, noting challenges regarding capturing possible treatment pathways (6/15), estimates of prior treatment exposure effect (5/15), definitions of best supportive care (3/15), and the heterogeneity observed in the indirect treatment comparisons used to inform the models (13/15). Two HTAs were general landscape reviews not assessing individual treatments for recommendation. Of the remaining, most resulted in positive recommendation (12/13) and, amongst these, preceding treatments put downward pressure on price and limited the population indicated (12/12), although recommendations were sometimes restricted to even smaller subgroups (2/12).

CONCLUSIONS: Unique considerations emerged when reviewing economic models for new treatments in crowded landscapes. When preparing new models in these conditions, manufacturers should be aware of the influence of past submissions and will need to source compelling, high-quality evidence to justify deviation from precedent. They should carefully consider uncertainty regarding the role and impact of alternative treatments, and submitters should be prepared for indication and price limitations driven by alternate treatments.