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November 2017

Restricted Mean Survival Time as a Measure to Interpret Clinical Trial Results

Author Affiliations
  • 1Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women’s Hospital, Boston, Massachusetts
  • 2Division of Gerontology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts
  • 3Division of Population Sciences, Department of Medical Oncology, Dana Farber Cancer Institute, Boston, Massachusetts
  • 4Department of Biostatistics, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
JAMA Cardiol. 2017;2(11):1179-1180. doi:10.1001/jamacardio.2017.2922

Clinical trials of cardiovascular therapeutics have been criticized for underrepresentation of older adults with frailty and multiple chronic conditions. Major strides have been made in the past decade to increase representation of this population, as exemplified by clinical trials of transcatheter aortic valve replacement (TAVR).1,2 While more high-quality evidence is being generated to guide treatment in older adults, the challenge remains to interpret treatment effect in a manner that is informative and intuitive to clinical communities. This is particularly important for older adults with frailty and with limited life expectancy in whom the expected benefit may be too small or remote to justify the risk of treatment-related adverse events. Most cardiovascular trials conventionally report treatment effect in terms of relative risk reduction (eg, hazard ratio [HR]) and absolute risk reduction (or equivalently, number needed to treat) for deaths or cardiovascular events at a specific point. In 2010, restricted mean survival time (RMST) was proposed as an alternative measure of treatment effect that offers some advantages in design, analysis, and interpretation over the conventional measures.3-5 In this Viewpoint, we explain how different measures of treatment effect are interpreted for evidence-based communication and their caveats using the 5-year follow-up data from the Placement of Aortic Transcatheter Valves (PARTNER) A and B trials1,2 as an example.