A Guide to Selecting Flexible Survival Models to Inform Economic Evaluations of Cancer Immunotherapies

Stephen Palmer, Isabelle Borget, Tim Friede, Don Husereau, Jonathan Karnon, Ben Kearns, Emma Medin, Elisabeth F.P. Peterse, Sven L. Klijn, Elisabeth J.M. Verburg-Baltussen, Elisabeth Fenwick, John Borrill

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)
46 Downloads (Pure)


Objectives: Parametric models are routinely used to estimate the benefit of cancer drugs beyond trial follow-up. The advent of immune checkpoint inhibitors has challenged this paradigm, and emerging evidence suggests that more flexible survival models, which can better capture the shapes of complex hazard functions, might be needed for these interventions. Nevertheless, there is a need for an algorithm to help analysts decide whether flexible models are required and, if so, which should be chosen for testing. This position article has been produced to bridge this gap. 

Methods: A virtual advisory board comprising 7 international experts with in-depth knowledge of survival analysis and health technology assessment was held in summer 2021. The experts discussed 24 questions across 6 topics: the current survival model selection procedure, data maturity, heterogeneity of treatment effect, cure and mortality, external evidence, and additions to existing guidelines. Their responses culminated in an algorithm to inform selection of flexible survival models. 

Results: The algorithm consists of 8 steps and 4 questions. Key elements include the systematic identification of relevant external data, using clinical expert input at multiple points in the selection process, considering the future and the observed hazard functions, assessing the potential for long-term survivorship, and presenting results from all plausible models. 

Conclusions: This algorithm provides a systematic, evidence-based approach to justify the selection of survival extrapolation models for cancer immunotherapies. If followed, it should reduce the risk of selecting inappropriate models, partially addressing a key area of uncertainty in the economic evaluation of these agents.

Original languageEnglish
Pages (from-to)185-192
Number of pages8
JournalValue in Health
Issue number2
Early online date13 Aug 2022
Publication statusPublished - Feb 2023


  • algorithm
  • cancer
  • extrapolation
  • immunotherapy
  • survival analysis


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