Analyzing overall survival in randomized controlled trials with crossover and implications for economic evaluation

Linus Jönsson*, Rickard Sandin, Mattias Ekman, Joakim Ramsberg, Claudie Charbonneau, Xin Huang, Bengt Jönsson, Milton C. Weinstein, Michael Drummond

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Offering patients in oncology trials the opportunity to cross over to active treatment at disease progression is a common strategy to address ethical issues associated with placebo controls but may lead to statistical challenges in the analysis of overall survival and cost-effectiveness because crossover leads to information loss and dilution of comparative clinical efficacy. Objectives: We provide an overview of how to address crossover, implications for risk-effect estimates of survival (hazard ratios) and cost-effectiveness, and how this influences decisions of reimbursement agencies. Two case studies using data from two phase III sunitinib oncology trials are used as illustration. Methods: We reviewed the literature on statistical methods for adjusting for crossover and recent health technology assessment decisions in oncology. Results: We show that for a trial with a high proportion of crossover from the control arm to the investigational arm, the choice of the statistical method greatly affects treatment-effect estimates and cost-effectiveness because the range of relative mortality risk for active treatment versus control is broad. With relatively frequent crossover, one should consider either the inverse probability of censoring weighting or the rank-preserving structural failure time model to minimize potential bias, with choice dependent on crossover characteristics, trial size, and available data. A large proportion of crossover favors the rank-preserving structural failure time model, while large sample size and abundant information about confounding factors favors the inverse probability of censoring weighting model. When crossover is very infrequent, methods yield similar results. Conclusions: Failure to correct for crossover may lead to suboptimal decisions by pricing and reimbursement authorities, thereby limiting an effective drug's potential.

Original languageEnglish
Pages (from-to)707-713
Number of pages7
JournalValue in Health
Volume17
Issue number6
DOIs
Publication statusPublished - Sept 2014

Keywords

  • cost effectiveness
  • crossover
  • oncology
  • sunitinib
  • surviva

Cite this