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Comparing methods to combine functional loss and mortality in clinical trials for amyotrophic lateral sclerosis

Authors van Eijk RPA, Eijkemans MJC, Rizopoulos D, van den Berg LH, Nikolakopoulos S

Received 4 October 2017

Accepted for publication 28 December 2017

Published 19 March 2018 Volume 2018:10 Pages 333—341


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Professor Lars Pedersen

Ruben PA van Eijk,1 Marinus JC Eijkemans,2 Dimitris Rizopoulos,3 Leonard H van den Berg,4,* Stavros Nikolakopoulos5,*

1Department of Neurology, University Medical Center Utrecht, Utrecht, the Netherlands; 2Department of Biostatistics, University Medical Center Utrecht, Utrecht, the Netherlands; 3Department of Biostatistics, Erasmus University Medical Center, Rotterdam, the Netherlands; 4Department of Neurology, University Medical Center Utrecht, Utrecht, the Netherlands; 5Department of Biostatistics, University Medical Center Utrecht, Utrecht, the Netherlands

*These authors contributed equally to this work

Objective: Amyotrophic lateral sclerosis (ALS) clinical trials based on single end points only partially capture the full treatment effect when both function and mortality are affected, and may falsely dismiss efficacious drugs as futile. We aimed to investigate the statistical properties of several strategies for the simultaneous analysis of function and mortality in ALS clinical trials.
Methods: Based on the Pooled Resource Open-Access ALS Clinical Trials (PRO-ACT) database, we simulated longitudinal patterns of functional decline, defined by the revised amyotrophic lateral sclerosis functional rating scale (ALSFRS-R) and conditional survival time. Different treatment scenarios with varying effect sizes were simulated with follow-up ranging from 12 to 18 months. We considered the following analytical strategies: 1) Cox model; 2) linear mixed effects (LME) model; 3) omnibus test based on Cox and LME models; 4) composite time-to-6-point decrease or death; 5) combined assessment of function and survival (CAFS); and 6) test based on joint modeling framework. For each analytical strategy, we calculated the empirical power and sample size.
Results: Both Cox and LME models have increased false-negative rates when treatment exclusively affects either function or survival. The joint model has superior power compared to other strategies. The composite end point increases false-negative rates among all treatment scenarios. To detect a 15% reduction in ALSFRS-R decline and 34% decline in hazard with 80% power after 18 months, the Cox model requires 524 patients, the LME model 794 patients, the omnibus test 526 patients, the composite end point 1,274 patients, the CAFS 576 patients and the joint model 464 patients.
Conclusion: Joint models have superior statistical power to analyze simultaneous effects on survival and function and may circumvent pitfalls encountered by other end points. Optimizing trial end points is essential, as selecting suboptimal outcomes may disguise important treatment clues.

Keywords: joint models, CAFS, clinical trials, amyotrophic lateral sclerosis

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