Life expectancy difference and life expectancy ratio: two measures of treatment effects in randomised trials with non-proportional hazards.
Where this comes from
- Record sourced from PubMed, PMID 28546261.
- Also identified by DOI 10.1136/bmj.j2250 and PMC identifier 5444092.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The hazard ratio (HR) is the most common measure of treatment effect in clinical trials that use time-to-event outcomes such as survival. When survival curves cross over or separate only after a considerable time, the proportional hazards assumption of the Cox model is violated, and HR can be misleading. We present two measures of treatment effects for situations where the HR changes over time: the life expectancy difference (LED) and life expectancy ratio (LER). LED is the difference between mean survival times in the intervention and control arms. LER is the ratio of these two times. LED and LER can be calculated for at least two time intervals during the trial, allowing for curves where the treatment effect changes over time. The two measures are readily interpretable as absolute and relative gains or losses in life expectancy.
Medical subject headings
- Data Interpretation, Statistical
- Humans
- Kaplan-Meier Estimate
- Life Expectancy
- Randomized Controlled Trials as Topic
- Randomized Controlled Trials as Topic/methods