Years-needed-to-treat to add 1 year of life: a new metric to estimate treatment effects in randomized trials.
OBJECTIVE
A standard metric to estimate absolute treatment effects is numbers-needed-to-treat (NNT), which implicitly assumes that all benefits reverse at trial-end. However, in-trial survival benefits typically do not reverse until long after trial-end, so that NNT will substantially underestimate lifetime benefits.


RESULTS
We developed a new concept, years-needed-to-treat (YNT) to add 1 year of life, that quantifies the expected average life expectancy for two treatments including the estimated years of life remaining post-trial. Numbers-needed-to-treat and YNT were calculated in the COMET trial, in which carvedilol vs. metoprolol tartrate resulted in 17% lower mortality over 4.8 years. A multivariate Cox model was used to predict survival. Remaining years of life were estimated using the mortality-life-table method. At trial-end, survival was 9% higher in the carvedilol arm. Assuming that patients remained on the same therapy post-trial, the average total years of life for carvedilol vs. metoprolol were 10.63 +/- 0.19 vs. 9.48 +/- 0.18 (P < 0.0001) or 1.15 (95% confidence interval 0.64-1.66) additional years of life. The YNT was 9.2, indicating that 9.2 person-years of treatment added 1 person-year of life, compared with NNT of 59.


CONCLUSIONS
Compared with NNT, the YNT method more accurately accounts for potential long-term benefits of interventions in randomized trials.
Levy
Wayne C
WC
Division of Cardiology, University of Washington, Box 356422, 1959 NE Pacific Street, Seattle, WA 98177, USA. levywc@u.washington.edu
Mozaffarian
Dariush
D
Linker
David T
DT
Kenyon
Kenneth W
KW
Cleland
John G F
JG
Komajda
Michel
M
Remme
Willem J
WJ
Torp-Pedersen
Christian
C
Metra
Marco
M
Poole-Wilson
Philip A
PA
D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage / Q000627:therapeutic use*; D002227:Carbazoles / Q000008:administration & dosage / Q000627:therapeutic use*; D000077261:Carvedilol; D016001:Confidence Intervals; D005500:Follow-Up Studies; D006333:Heart Failure / Q000188:drug therapy* / Q000401:mortality*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008017:Life Expectancy / Q000639:trends*; D008790:Metoprolol / Q000008:administration & dosage / Q000627:therapeutic use*; D016017:Odds Ratio; D011412:Propanolamines / Q000008:administration & dosage / Q000627:therapeutic use*; D015996:Survival Rate / Q000639:trends; D013997:Time Factors; D016896:Treatment Outcome
D000319:Adrenergic beta-Antagonists; D002227:Carbazoles; D011412:Propanolamines; D000077261:Carvedilol; D008790:Metoprolol